Southern Company 10-K 2021-12-31

Table of Contents Index to Financial Statements

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

☑ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

For the Fiscal Year Ended December 31, 2021

OR

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)

OF THE SECURITIES EXCHANGE ACT OF 1934

For the Transition Period from to

(A Delaware Corporation)

30 Ivan Allen Jr. Boulevard, N.W.

Atlanta, Georgia 30308

(404) 506-5000

(An Alabama Corporation)

600 North 18th Street

Birmingham, Alabama 35203

(205) 257-1000

(A Georgia Corporation)

241 Ralph McGill Boulevard, N.E.

Atlanta, Georgia 30308

(404) 506-6526

(A Mississippi Corporation)

2992 West Beach Boulevard

Gulfport, Mississippi 39501

(228) 864-1211

(A Delaware Corporation)

30 Ivan Allen Jr. Boulevard, N.W.

Atlanta, Georgia 30308

(404) 506-5000

(A Georgia Corporation)

Ten Peachtree Place, N.E.

Atlanta, Georgia 30309

(404) 584-4000

Table of Contents Index to Financial Statements

Securities registered pursuant to Section 12(b) of the Act:

**Securities registered pursuant to Section 12(g) of the Act:*()

(*)At December 31, 2021

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ¨ No x (Response applicable to all registrants.)

Indicate by check mark whether the registrants (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrants were required to file such reports), and (2) have been subject to such filing requirements for the past 90 days. Yes x No ¨

Indicate by check mark whether the registrants have submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrants were required to submit such files). Yes x No ¨

Table of Contents Index to Financial Statements

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No x (Response applicable to all registrants.)

Aggregate market value of The Southern Company's common stock held by non-affiliates of The Southern Company at June 30, 2021: $64.1 billion. All of the common stock of the other registrants is held by The Southern Company. A description of each registrant's common stock follows:

Documents incorporated by reference: specified portions of The Southern Company's Definitive Proxy Statement on Schedule 14A relating to the 2022 Annual Meeting of Stockholders are incorporated by reference into PART III. In addition, specified portions of Alabama Power Company's Definitive Proxy Statement on Schedule 14A relating to its 2022 Annual Meeting of Shareholders are incorporated by reference into PART III.

Each of Georgia Power Company, Mississippi Power Company, Southern Power Company, and Southern Company Gas meets the conditions set forth in General Instructions I(1)(a) and (b) of Form 10-K and is therefore filing this Form 10-K with the reduced disclosure format specified in General Instructions I(2)(b), (c), and (d) of Form 10-K.

This combined Form 10-K is separately filed by The Southern Company, Alabama Power Company, Georgia Power Company, Mississippi Power Company, Southern Power Company, and Southern Company Gas. Information contained herein relating to any individual registrant is filed by such registrant on its own behalf. Each registrant makes no representation as to information relating to the other registrants.

Table of Contents Index to Financial Statements

Table of Contents

i

Table of Contents Index to Financial Statements

DEFINITIONS

When used in this Form 10-K, the following terms will have the meanings indicated.

ii

Table of Contents Index to Financial Statements

DEFINITIONS

(continued)

iii

Table of Contents Index to Financial Statements

DEFINITIONS

(continued)

iv

Table of Contents Index to Financial Statements

DEFINITIONS

(continued)

v

Table of Contents Index to Financial Statements

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION

This Annual Report on Form 10-K contains forward-looking statements. Forward-looking statements include, among other things, statements concerning the potential and expected effects of the COVID-19 pandemic, regulated rates, the strategic goals for the business, customer and sales growth, economic conditions, cost recovery and other rate actions, projected equity ratios, current and proposed environmental regulations and related compliance plans and estimated expenditures, GHG emissions reduction goals, pending or potential litigation matters, access to sources of capital, projections for the qualified pension plans, postretirement benefit plans, and nuclear decommissioning trust fund contributions, financing activities, completion dates and costs of construction projects, matters related to the abandonment of the Kemper IGCC, completion of announced acquisitions, filings with state and federal regulatory authorities, federal and state income tax benefits, estimated sales and purchases under power sale and purchase agreements, and estimated construction plans and expenditures. In some cases, forward-looking statements can be identified by terminology such as "may," "will," "could," "would," "should," "expects," "plans," "anticipates," "believes," "estimates," "projects," "predicts," "potential," or "continue" or the negative of these terms or other similar terminology. There are various factors that could cause actual results to differ materially from those suggested by the forward-looking statements; accordingly, there can be no assurance that such indicated results will be realized. These factors include:

• the impact of recent and future federal and state regulatory changes, including tax, environmental, and other laws and regulations to which Southern Company and its subsidiaries are subject, as well as changes in application of existing laws and regulations;

• the potential effects of the continued COVID-19 pandemic, including, but not limited to, those described in Item 1A "Risk Factors" herein;

• the extent and timing of costs and legal requirements related to CCR;

• current and future litigation or regulatory investigations, proceedings, or inquiries, including litigation and other disputes related to the Kemper County energy facility;

• the effects, extent, and timing of the entry of additional competition in the markets in which Southern Company's subsidiaries operate, including from the development and deployment of alternative energy sources;

• variations in demand for electricity and natural gas;

• available sources and costs of natural gas and other fuels;

• the ability to complete necessary or desirable pipeline expansion or infrastructure projects, limits on pipeline capacity, and operational interruptions to natural gas distribution and transmission activities;

• transmission constraints;

• effects of inflation;

• the ability to control costs and avoid cost and schedule overruns during the development, construction, and operation of facilities or other projects, including Plant Vogtle Units 3 and 4 (which includes components based on new technology that only within the last few years began initial operation in the global nuclear industry at this scale) and Plant Barry Unit 8, due to current and/or future challenges which include, but are not limited to, changes in labor costs, availability, and productivity; challenges with management of contractors or vendors; subcontractor performance; adverse weather conditions; shortages, delays, increased costs, or inconsistent quality of equipment, materials, and labor; contractor or supplier delay; delays due to judicial or regulatory action; nonperformance under construction, operating, or other agreements; operational readiness, including specialized operator training and required site safety programs; engineering or design problems or any remediation related thereto; design and other licensing-based compliance matters, including, for nuclear units, inspections and the timely submittal by Southern Nuclear of the ITAAC documentation for each unit and the related investigations, reviews, and approvals by the NRC necessary to support NRC authorization to load fuel; challenges with start-up activities, including major equipment failure, or system integration; and/or operational performance; and challenges related to the COVID-19 pandemic;

• the ability to overcome or mitigate the current challenges at Plant Vogtle Units 3 and 4, as described in Note 2 to the financial statements under "Georgia Power – Nuclear Construction" in Item 8 herein, that could further impact the cost and schedule for the project;

• legal proceedings and regulatory approvals and actions related to construction projects, such as Plant Vogtle Units 3 and 4 and Plant Barry Unit 8, including PSC approvals and FERC and NRC actions;

• under certain specified circumstances, a decision by holders of more than 10% of the ownership interests of Plant Vogtle Units 3 and 4 not to proceed with construction and the ability of other Vogtle Owners to tender a portion of their ownership interests to Georgia Power following certain construction cost increases;

vi

Table of Contents Index to Financial Statements

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING INFORMATION

(continued)

• in the event Georgia Power becomes obligated to provide funding to MEAG Power with respect to the portion of MEAG Power's ownership interest in Plant Vogtle Units 3 and 4 involving JEA, any inability of Georgia Power to receive repayment of such funding;

• the ability to construct facilities in accordance with the requirements of permits and licenses (including satisfaction of NRC requirements), to satisfy any environmental performance standards and the requirements of tax credits and other incentives, and to integrate facilities into the Southern Company system upon completion of construction;

• investment performance of the employee and retiree benefit plans and nuclear decommissioning trust funds;

• advances in technology, including the pace and extent of development of low- to no-carbon energy technologies and negative carbon concepts;

• performance of counterparties under ongoing renewable energy partnerships and development agreements;

• state and federal rate regulations and the impact of pending and future rate cases and negotiations, including rate actions relating to ROE, equity ratios, additional generating capacity, and fuel and other cost recovery mechanisms;

• the ability to successfully operate the electric utilities' generating, transmission, and distribution facilities, Southern Power's generation facilities, and Southern Company Gas' natural gas distribution and storage facilities and the successful performance of necessary corporate functions;

• the inherent risks involved in operating and constructing nuclear generating facilities;

• the inherent risks involved in transporting and storing natural gas;

• the performance of projects undertaken by the non-utility businesses and the success of efforts to invest in and develop new opportunities;

• internal restructuring or other restructuring options that may be pursued;

• potential business strategies, including acquisitions or dispositions of assets or businesses, which cannot be assured to be completed or beneficial to Southern Company or its subsidiaries;

• the ability of counterparties of Southern Company and its subsidiaries to make payments as and when due and to perform as required;

• the ability to obtain new short- and long-term contracts with wholesale customers;

• the direct or indirect effect on the Southern Company system's business resulting from cyber intrusion or physical attack and the threat of physical attacks;

• interest rate fluctuations and financial market conditions and the results of financing efforts;

• access to capital markets and other financing sources;

• changes in Southern Company's and any of its subsidiaries' credit ratings;

• the replacement of LIBOR with an alternative reference rate;

• the ability of Southern Company's electric utilities to obtain additional generating capacity (or sell excess generating capacity) at competitive prices;

• catastrophic events such as fires, earthquakes, explosions, floods, tornadoes, hurricanes and other storms, droughts, pandemic health events, political unrest, or other similar occurrences;

• the direct or indirect effects on the Southern Company system's business resulting from incidents affecting the U.S. electric grid, natural gas pipeline infrastructure, or operation of generating or storage resources;

• impairments of goodwill or long-lived assets;

• the effect of accounting pronouncements issued periodically by standard-setting bodies; and

• other factors discussed elsewhere herein and in other reports filed by the Registrants from time to time with the SEC.

The Registrants expressly disclaim any obligation to update any forward-looking statements.

vii

Table of Contents Index to Financial Statements

PART I

Southern Company is a holding company that owns all of the outstanding common stock of three traditional electric operating companies, Southern Power Company, and Southern Company Gas.

• The traditional electric operating companies – Alabama Power, Georgia Power, and Mississippi Power – are each operating public utility companies providing electric service to retail customers in three Southeastern states in addition to wholesale customers in the Southeast.

• Southern Power Company is also an operating public utility company. The term "Southern Power" when used herein refers to Southern Power Company and its subsidiaries, while the term "Southern Power Company" when used herein refers only to the Southern Power parent company. Southern Power develops, constructs, acquires, owns, and manages power generation assets, including renewable energy projects, and sells electricity at market-based rates in the wholesale market.

• Southern Company Gas is an energy services holding company whose primary business is the distribution of natural gas in four states – Illinois, Georgia, Virginia, and Tennessee – through the natural gas distribution utilities. Southern Company Gas is also involved in several other businesses that are complementary to the distribution of natural gas.

Southern Company also owns SCS, Southern Linc, Southern Holdings, Southern Nuclear, PowerSecure, and other direct and indirect subsidiaries. SCS, the system service company, has contracted with Southern Company, each traditional electric operating company, Southern Power, Southern Company Gas, Southern Nuclear, SEGCO, and other subsidiaries to furnish, at direct or allocated cost and upon request, the following services: general executive and advisory, general and design engineering, operations, purchasing, accounting, finance, treasury, legal, tax, information technology, marketing, auditing, insurance and pension administration, human resources, systems and procedures, digital wireless communications, cellular tower space, and other services with respect to business and operations, construction management, and Southern Company power pool transactions. Southern Linc provides digital wireless communications for use by Southern Company and its subsidiary companies and also markets these services to the public and provides fiber optics services through its subsidiary, Southern Telecom, Inc. Southern Linc's system covers approximately 127,000 square miles in the Southeast. Southern Holdings is an intermediate holding company subsidiary, which invests in various projects. During 2021, Southern Holdings sold or terminated three of its leveraged lease investments and only one remains. Southern Nuclear operates and provides services to the Southern Company system's nuclear power plants and is currently managing construction of and developing Plant Vogtle Units 3 and 4, which are co-owned by Georgia Power. PowerSecure develops distributed energy and resilience solutions and deploys microgrids for commercial, industrial, governmental, and utility customers.

See "The Southern Company System" herein for additional information. Also see Note 15 to the financial statements in Item 8 herein for information regarding recent acquisition and disposition activity. Segment information for Southern Company and Southern Company Gas is included in Note 16 to the financial statements in Item 8 herein.

The Registrants' Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, and any amendments to those reports are made available on Southern Company's website, free of charge, as soon as reasonably practicable after such material is electronically filed with or furnished to the SEC. Southern Company's internet address is www.southerncompany.com.

The Southern Company System

Traditional Electric Operating Companies

The traditional electric operating companies are vertically integrated utilities that own generation, transmission, and distribution facilities. See PROPERTIES in Item 2 herein for additional information on the traditional electric operating companies' generating facilities. Each company's transmission facilities are connected to the respective company's own generating plants and other sources of power (including certain generating plants owned by Southern Power) and are interconnected with the transmission facilities of the other traditional electric operating companies and SEGCO. For information on the State of Georgia's integrated transmission system, see "Territory Served by the Southern Company System – Traditional Electric Operating Companies and Southern Power" herein.

Agreements in effect with principal neighboring utility systems provide for capacity and energy transactions that may be entered into for reasons related to reliability or economics. Additionally, the traditional electric operating companies have entered into various reliability agreements with certain neighboring utilities, each of which provides for the establishment and periodic review of principles and procedures for planning and operation of generation and transmission facilities, maintenance schedules, load retention programs, emergency operations, and other matters affecting the reliability of bulk power supply. The traditional electric operating companies have joined with other utilities in the Southeast to form the SERC to augment further

I-1

Table of Contents Index to Financial Statements

the reliability and adequacy of bulk power supply. Through the SERC, the traditional electric operating companies are represented at the North American Electric Reliability Corporation. In February 2021, Southern Company joined a filing at the FERC proposing a Southeast Energy Exchange Market (SEEM) that included many of the other electric service providers in the Southeast. In October 2021, the proposal became effective by operation of law following a tie vote by the FERC, subject to certain rehearing requests. A petition for appeal has been filed regarding the FERC's orders. SEEM is an extension of the existing bilateral market where participants will use an automated, intra-hour energy exchange to buy and sell power close to the time the energy is consumed, utilizing available unreserved transmission. SEEM is expected to begin service in mid-2022. The ultimate outcome of this matter cannot be determined at this time.

The utility assets of the traditional electric operating companies and certain utility assets of Southern Power Company are operated as a single integrated electric system, or Southern Company power pool, pursuant to the IIC. Activities under the IIC are administered by SCS, which acts as agent for the traditional electric operating companies and Southern Power Company. The fundamental purpose of the Southern Company power pool is to provide for the coordinated operation of the electric facilities in an effort to achieve the maximum possible economies consistent with the highest practicable reliability of service. Subject to service requirements and other operating limitations, system resources are committed and controlled through the application of centralized economic dispatch. Under the IIC, each traditional electric operating company and Southern Power Company retains its lowest cost energy resources for the benefit of its own customers and delivers any excess energy to the Southern Company power pool for use in serving customers of other traditional electric operating companies or Southern Power Company or for sale by the Southern Company power pool to third parties. The IIC provides for the recovery of specified costs associated with the affiliated operations thereunder, as well as the proportionate sharing of costs and revenues resulting from Southern Company power pool transactions with third parties. In connection with the sale of former subsidiary Gulf Power in January 2019, an

Showing the first 8K of 72K characters. Open the full section

In addition to the other information in this Form 10-K, including MANAGEMENT'S DISCUSSION AND ANALYSIS – FUTURE EARNINGS POTENTIAL in Item 7, and other documents filed by Southern Company and/or its subsidiaries with the SEC, the following factors should be carefully considered in evaluating Southern Company and its subsidiaries. Such factors could affect actual results and cause results to differ materially from those expressed in any forward-looking statements made by, or on behalf of, Southern Company and/or its subsidiaries. The risk factors discussed below could adversely affect a Registrant's results of operations, financial condition, liquidity, and cash flow, as well as cause reputational damage.

UTILITY REGULATORY, LEGISLATIVE, AND LITIGATION RISKS

Southern Company and its subsidiaries are subject to substantial federal, state, and local governmental regulation, including with respect to rates. Compliance with current and future regulatory requirements and procurement of necessary approvals, permits, and certificates may result in substantial costs to Southern Company and its subsidiaries.

Laws and regulations govern the terms and conditions of the services the Southern Company system offers, protection of critical electric infrastructure assets, transmission planning, reliability, pipeline safety, interaction with wholesale markets, and relationships with affiliates, among other matters. The Registrants' businesses are subject to regulatory regimes which could result in substantial monetary penalties if a Registrant is found to be noncompliant.

The profitability of the traditional electric operating companies' and the natural gas distribution utilities' businesses is largely dependent on their ability, through the rates that they are permitted to charge, to recover their costs and earn a reasonable rate of return on invested capital. The traditional electric operating companies and the natural gas distribution utilities seek to recover their costs, including compliance costs (including a reasonable return on invested capital), through their retail rates, which must be approved by the applicable state PSC or other applicable state regulatory agency. Such regulators, in a future rate proceeding, may alter the timing or amount of certain costs for which recovery is allowed or modify the current authorized rate of return. Rate refunds may also be required. Additionally, the rates charged to wholesale customers by the traditional electric operating companies and Southern Power and the rates charged to natural gas transportation customers by Southern Company Gas' pipeline investments and for some of its storage assets must be approved by the FERC. Changes to Southern Power's and the traditional electric operating companies' ability to conduct business pursuant to FERC market-based rate authority could affect wholesale rates. Also, while a small percentage of transmission revenues are collected through wholesale electric tariffs, the majority are collected through retail rates. Transmission planning could be impacted by FERC policy changes.

The impact of any future revision or changes in interpretations of existing regulations or the adoption of new laws and regulations applicable to Southern Company or any of its subsidiaries is uncertain. Changes in regulation, the imposition of additional regulations, changes in enforcement practices of regulators, or penalties imposed for noncompliance with existing laws or regulations could influence the operating environment of the Southern Company system and may result in substantial costs.

The Southern Company system's costs of compliance with environmental laws and satisfying related AROs are significant.

The Southern Company system's operations are regulated by state and federal environmental agencies through a variety of laws and regulations governing air, GHGs, water, land, avian and other wildlife and habitat protection, and other natural resources. Compliance with existing environmental requirements involves significant capital and operating costs including the settlement of AROs, a major portion of which is expected to be recovered through retail and wholesale rates. There is no assurance, however, that all such costs will be recovered. The Registrants expect future compliance expenditures will continue to be significant.

The EPA has adopted and is implementing regulations governing air and GHG emissions under the Clean Air Act and water quality under the Clean Water Act. The EPA and certain states have also adopted and continue to propose regulations governing the disposal and management of CCR at power plant sites. The cost estimates for AROs related to the disposal of CCR are based on information using various assumptions related to closure and post-closure costs, timing of future cash outlays, inflation and discount rates, and the potential compliance methods. The traditional electric operating companies will continue to periodically update their ARO cost estimates.

Additionally, environmental laws and regulations covering the handling and disposal of waste and release of hazardous substances could require the Southern Company system to incur substantial costs to clean up affected sites, including certain current and former operating sites, and locations subject to contractual obligations.

Litigation over environmental issues and claims of various types, including property damage, personal injury, and citizen enforcement of environmental requirements has occurred throughout the U.S. This litigation has included, but is not limited to,

I-15

Table of Contents Index to Financial Statements

claims for damages alleged to have been caused by CO2 and other emissions, CCR, releases of regulated substances, alleged exposure to regulated substances, and/or requests for injunctive relief in connection with such matters.

Compliance with any new or revised environmental laws or regulations could affect many areas of operations for the Southern Company system. The Southern Company system's ultimate environmental compliance strategy and future environmental expenditures will depend on various factors, such as state adoption and implementation of requirements, the availability and cost of any deployed control technology, fuel prices, and the outcome of pending and/or future legal challenges. Compliance costs may result from the installation of additional environmental controls, closure and monitoring of CCR facilities, unit retirements, operational changes, or changing fuel sources for certain existing units, as well as related upgrades to the Southern Company system's transmission and distribution (electric and natural gas) systems. Environmental compliance spending over the next several years may differ materially from the amounts estimated and could adversely affect the Registrants if such costs cannot continue to be recovered on a timely basis. Further, increased costs that are recovered through regulated rates could contribute to reduced demand for electricity and natural gas. Additionally, many commercial and industrial customers may also be affected by existing and future environmental requirements, which for some may have the potential to reduce their demand for electricity or natural gas.

The Southern Company system may be exposed to regulatory and financial risks related to the impact of GHG legislation, regulation, and emission reduction goals.

Concern and activism about climate change continue to increase and, as a result, demand for energy conservation and sustainable assets could further increase. Additionally, costs associated with GHG legislation, regulation, and emission reduction goals could be significant.

The Southern Company system has robust processes for identifying, assessing, and responding to climate-related risks, including a scen

Showing the first 8K of 68K characters. Open the full section

None.

I-26

Table of Contents Index to Financial Statements

Electric

The traditional electric operating companies, Southern Power, and SEGCO, at December 31, 2021, owned and/or operated 30 hydroelectric generating stations, 24 fossil fuel generating stations, three nuclear generating stations, 13 combined cycle/cogeneration stations, 45 solar facilities, 15 wind facilities, one fuel cell facility, and four battery storage facilities. The amounts of capacity for each company at December 31, 2021 are shown in the table below. The traditional electric operating companies have certain jointly-owned generating stations. For these facilities, the nameplate capacity shown represents the Registrant's portion of total plant capacity, with ownership percentages provided if less than 100%. See "Jointly-Owned Facilities" and "Titles to Property" herein and Note 5 to the financial statements under "Joint Ownership Agreements" in Item 8 herein for additional information.

I-27

Table of Contents Index to Financial Statements

I-28

Table of Contents Index to Financial Statements

I-29

Table of Contents Index to Financial Statements

I-30

Table of Contents Index to Financial Statements

(a)Alabama Power and Georgia Power each own 50% of the outstanding common stock of SEGCO, an operating public utility company. Alabama Power and Georgia Power are each entitled to one-half of SEGCO's capacity and energy. Alabama Power acts as SEGCO's agent in the operation of SEGCO's units and furnishes fuel to SEGCO for its units. See Note 7 to the financial statements under "SEGCO" in Item 8 herein for additional information.

(b)Generation is dedicated to a single industrial customer. See MANAGEMENT'S DISCUSSION AND ANALYSIS – FINANCIAL CONDITION AND LIQUIDITY – "Credit Rating Risk" in Item 7 herein.

(c)Operated by OPC.

(d)Southern Power owns a 67% equity interest in SP Solar (a limited partnership indirectly owning all of Southern Power's solar facilities, except the Roserock and Gaskell West I solar facilities). SP Solar is the 51% majority owner of Boulder I, Garland, Henrietta, Imperial Valley, Lost Hills Blackwell, North Star, and Tranquillity solar facilities; the 66% majority owner of Desert Stateline solar facility; and the sole owner of the remaining SP Solar solar facilities. Southern Power owns 100% of Roserock and is also the controlling partner in a tax equity partnership owning Gaskell West I. All of these entities are consolidated subsidiaries of Southern Power and the capacity shown in the table is 100% of the nameplate capacity for the respective facility.

(e)Southern Power is the controlling member in SP Wind (a tax equity entity owning eight of Southern Power's wind facilities). SP Wind is the 90.1% majority owner of Wake Wind and owns 100% of the remaining SP Wind facilities. Southern Power is the controlling partner in other tax equity partnerships owning Cactus Flats, Wildhorse Mountain, Reading, Skookumchuck, and Deuel Harvest (additionally for Skookumchuck and Deuel Harvest, a noncontrolling interest in Southern Power's remaining equity is owned by another partner). Southern Power owns 100% of Glass Sands and is also the controlling member in a non-tax equity partnership for Beech Ridge II. All of these entities are consolidated subsidiaries of Southern Power and the capacity shown in the table is 100% of the nameplate capacity for the respective facility.

(f)Southern Power has two noncontrolling interest partners that own approximately 10 MWs of the facility.

(g)The facility has a total nameplate capacity of 88 MWs, of which 73 MWs were placed in service during 2021 and the remaining MWs are expected to be placed in service later in the first quarter 2022.

(h)Southern Power has an equity method investment in the facility as the Class A member.

(i)The facility has a total nameplate capacity of 72 MWs, of which 32 MWs were placed in service during 2021 and the remaining MWs are expected to be placed in service later in the first quarter 2022.

(j)Southern Power is the controlling partner in a tax equity partnership owning the Garland and Tranquillity battery energy storage facilities. Additionally, the noncontrolling interests in Southern Power's remaining equity are owned by two other partners and the facilities are indirect subsidiaries of SP Solar.

I-31

Table of Contents Index to Financial Statements

See MANAGEMENT'S DISCUSSION AND ANALYSIS – FUTURE EARNINGS POTENTIAL – "Environmental Matters" in Item 7 herein and Note 2 to the financial statements under "Georgia Power – Integrated Resource Plan" and "Mississippi Power – Integrated Resource Plan" in Item 8 herein for information regarding plans to retire or convert to natural gas certain coal-fired generating capacity included in the table above.

Except as discussed below under "Titles to Property," the principal plants and other important units of the traditional electric operating companies, Southern Power, and SEGCO are owned in fee by the respective companies. It is the opinion of management of each such company that its operating properties are adequately maintained and are substantially in good operating condition, and suitable for their intended purpose.

Mississippi Power owns a 79-mile length of 500-kilovolt transmission line which is leased to Entergy Gulf States Louisiana, LLC. The line extends from Plant Daniel to the Louisiana state line. Entergy Gulf States Louisiana, LLC is paying a use fee through 2024 covering all expenses and the amortization of the original cost. At December 31, 2021, the unamortized portion was approximately $5 million.

Mississippi Power owns a lignite mine that was intended to provide fuel for the Kemper IGCC. Liberty Fuels Company, LLC, the operator of the mine, has a legal obligation to perform mine reclamation and Mississippi Power has a contractual obligation to fund all reclamation activities. As a result of the abandonment of the Kemper IGCC, final mine reclamation began in 2018 and was substantially completed in 2020, with monitoring expected to continue through 2028. See Note 3 to the financial statements under "Other Matters – Mississippi Power – Kemper County Energy Facility" in Item 8 herein for additional information.

In conjunction with Southern Company's sale of Gulf Power, Mississippi Power and Gulf Power agreed to seek a restructuring of their 50% undivided ownership interests in the Plant Daniel coal units such that each of them would, after the restructuring, own 100% of a generating unit. In 2019, Gulf Power provided notice to Mississippi Power that Gulf Power will retire its share of the coal generating capacity of Plant Daniel on January 15, 2024. Mississippi Power has the option to purchase Gulf Power's ownership interest for $1 on January 15, 2024, provided that Mississippi Power exercises the option no later than 120 days prior to that date. See Note 3 to the financial statements under "Other Matters – Mississippi Power – Plant Daniel" in Item 8 herein for additional information.

In 2021, the maximum demand on the traditional electric operating companies, Southern Power Company, and SEGCO was 33,373,000 KWs and occurred on July 29, 2021. The all-time maximum demand of 38,777,000 KWs on the traditional electric operating companies (including Gulf Power), Southern Power Company, and SEGCO occurred on August 22, 2007. These amounts exclude demand served by capacity retained by MEAG Power, OPC, and SEPA. The reserve margin for the traditional electric operating companies, Southern Power Company, and SEGCO in 2021 was 36%.

Jointly-Owned Facilities

Alabama Power, Georgia Power, and Mississippi Power at December 31, 2021 had undivided interests in certain generating plants and other related facilities with non-affiliated parties. The percentages of ownership of the total plant or facility are as follows:

Alabama Power, Georgia Power, and Mississippi Power have contracted to operate and maintain the respective units in which each has an interest (other than Rocky Mountain) as agent for the joint owners. Southern Nuclear operates and provides services to Alabama Power's and Georgia Power's nuclear plants.

I-32

Table of Contents Index to Financial Statements

In addition, Georgia Power has commitments, in the form of capacity purchases totaling $42 million, regarding a portion of a 5% interest in the original cost of Plant Vogtle Units 1 and 2 owned by MEAG Power that are in effect until the later of the retirement of the plant or the latest stated maturity date of MEAG Power's bonds issued to finance such ownership interest. See Note 3 to the financial statements under "Commitments" in Item 8 herein for additional information.

Construction continues on Plant Vogtle Units 3 and 4, which are jointly owned by the Vogtle Owners (with each owner holding the same undivided ownership interest as shown in the table above with respect to Plant Vogtle Units 1 and 2). See Note 2 to the financial statements under "Georgia Power – Nuclear Construction" in Item 8 herein.

Titles to Property

The traditional electric operating companies', Southern Power's, and SEGCO's interests in the principal plants and other important units of the respective companies are owned in fee by such companies, subject to the following major encumbrances: (1) a leasehold interest granted by Mississippi Power's largest retail customer, Chevron Products Company (Chevron), at the Chevron refinery, where five combustion turbines owned by Mississippi Power are located and used for co-generation, as well as liens on these assets pursuant to the related co-generation agreements and (2) liens associated with Georgia Power's reimbursement obligations to the DOE under its loan guarantee, which are secured by a first priority lien on (a) Georgia Power's undivided ownership interest in Plant Vogtle Units 3 and 4 and (b) Georgia Power's rights and obligations under the principal contracts relating to Plant Vogtle Units 3 and 4. See Note 5 to the financial statements under "Assets Subject to Lien" and Note 8 to the financial statements under "Long-term Debt" in Item 8 herein for additional information. The traditional electric operating companies own the fee interests in certain of their principal plants as tenants in common. See "Jointly-Owned Facilities" herein and Note 5 to the financial statements under "Joint Ownership Agreements" in Item 8 herein for additional information. Properties such as electric transmission and distribution lines, steam heating mains, and gas pipelines are constructed principally on rights-of-way, which are maintained under franchise or are held by easement only. A substantial portion of lands submerged by reservoirs is held under flood right easements. In addition, certain of the renewable generating facilities occupy or use real property that is not owned, primarily through various leases, easements, rights-of-way, permits, or licenses from private landowners or governmental entities.

Natural Gas

Southern Company Gas considers its properties to be adequately maintained, substantially in good operating condition, and suitable for their intended purpose. The following sections provide the location and general character of the materially important properties that are used by the segments of Southern Company Gas. Substantially all of Nicor Gas' properties are subject to the lien of the indenture securing its first mortgage bonds. See Note 8 to the financial statements in Item 8 herein for additional information.

Distribution and Transmission Mains

Southern Company Gas' distribution systems transport natural gas from its pipeline suppliers to customers in its service areas. These systems consist primarily of distribution and transmission mains, compressor stations, peak shaving/storage plants, service lines, meters, and regulators. At December 31, 2021, Southern Company Gas' gas distribution operations segment owned 76,289 miles of underground distribution and transmission mains, which are located on easements or rights-of-way that generally provide for perpetual use.

Storage Assets

Gas Distribution Operations

Southern Company Gas owns and operates eight underground natural gas storage fields in Illinois with a total working capacity of approximately 150 Bcf, approximately 135 Bcf of which is usually cycled on an annual basis. This system is designed to meet about 50% of the estimated peak-day deliveries and approximately 40% of the normal winter deliveries in Illinois. This level of storage capability provides Nicor Gas with supply flexibility, improves the reliability of deliveries, and helps mitigate the risk associated with seasonal price movements.

Southern Company Gas also has four LNG plants located in Georgia and Tennessee with total LNG storage capacity of approximately 7.0 Bcf. In addition, Southern Company Gas owns two propane storage facilities in Virginia, each with storage capacity of approximately 0.3 Bcf. The LNG plants and propane storage facility are used by Southern Company Gas' gas distribution operations segment to supplement natural gas supply during peak usage periods.

I-33

Table of Contents Index to Financial Statements

All Other

Southern Company Gas subsidiaries own two high-deliverability natural gas storage and hub facilities that are included in the all other segment. Golden Triangle Storage, Inc. operates a storage facility in Texas consisting of two salt dome caverns. Central Valley Gas Storage, LLC operates a depleted field storage facility in California.

Jointly-Owned Properties

Southern Company Gas' gas pipeline investments segment has a 50% undivided ownership interest in a 115-mile pipeline facility in northwest Georgia that was placed in service in 2017. Southern Company Gas also has an agreement to lease its 50% undivided ownership in the pipeline facility. See Note 5 to the financial statements under "Joint Ownership Agreements" in Item 8 herein for additional information.

See Note 3 to the financial statements in Item 8 herein for descriptions of legal and administrative proceedings discussed therein. The Registrants' threshold for disclosing material environmental legal proceedings involving a governmental authority where potential monetary sanctions are involved is $1 million.

Not applicable.

I-34

Table of Contents Index to Financial Statements

INFORMATION ABOUT OUR EXECUTIVE OFFICERS – SOUTHERN COMPANY

(Identification of executive officers of Southern Company is inserted in Part I in accordance with Regulation S-K, Item 401) The ages of the officers set forth below are as of December 31, 2021.

Thomas A. Fanning

Chairman, President, and Chief Executive Officer

Age 64

First elected in 2003. Chairman and Chief Executive Officer since December 2010 and President since August 2010.

Daniel S. Tucker

Executive Vice President and Chief Financial Officer

Age 51

First elected in 2021. Executive Vice President and Chief Financial Officer since September 2021. Previously served as Executive Vice President, Chief Financial Officer, and Treasurer of Georgia Power from January 2021 to September 2021, Executive Vice President and Chief Financial Officer of Southern Company Gas from January 2019 to January 2021, and Treasurer of Southern Company and Senior Vice President and Treasurer of SCS from October 2015 to January 2019.

Bryan D. Anderson

Executive Vice President

Age 55

First elected in 2020. Executive Vice President and President of External Affairs since January 2021. Executive Vice President of SCS since November 2020. Previously served as Senior Vice President of SCS with responsibility for governmental affairs from January 2015 to November 2020.

Stanley W. Connally, Jr.

Executive Vice President of SCS

Age 52

First elected in 2012. Executive Vice President for Operations of SCS since June 2018. Previously served as President, Chief Executive Officer, and Director of Gulf Power from July 2012 through December 2018 and Chairman of Gulf Power's Board of Directors from July 2015 through December 2018.

Mark A. Crosswhite

Chairman, President and Chief Executive Officer of Alabama Power

Age 59

First elected in 2011. President, Chief Executive Officer, and Director of Alabama Power since March 2014. Chairman of Alabama Power's Board of Directors since May 2014.

Christopher Cummiskey

Executive Vice President

Age 47

First elected in 2021. Executive Vice President since January 2021. Chairman of Southern Power since February 2021 and Executive Vice President of SCS, Chief Executive Officer of Southern Power, and President and Chief Executive Officer of Southern PowerSecure Holdings, Inc. and Southern Holdings since July 2020. Previously served as Executive Vice President, External Affairs of Georgia Power from May 2015 to June 2020.

Martin B. Davis

Executive Vice President and Chief Information Officer

Age 58

First elected in 2021. Executive Vice President since April 2021. Chief Information Officer and Executive Vice President of SCS since July 2015. Previously served as Vice President from July 2015 through April 2021.

Kimberly S. Greene

Chairman, President, and Chief Executive Officer of Southern Company Gas

Age 55

First elected in 2013. Chairman, President, and Chief Executive Officer of Southern Company Gas since June 2018. Director of Southern Company Gas since July 2016. Previously served as Executive Vice President and Chief Operating Officer of Southern Company from March 2014 through June 2018.

I-35

Table of Contents Index to Financial Statements

James Y. Kerr II

Executive Vice President, Chief Legal Officer, and Chief Compliance Officer

Age 57

First elected in 2014. Executive Vice President, Chief Legal Officer (formerly known as General Counsel), and Chief Compliance Officer since March 2014.

Stephen E. Kuczynski

Chairman, President, and Chief Executive Officer of Southern Nuclear

Age 59

First elected in 2011. Chairman, President, and Chief Executive Officer of Southern Nuclear since July 2011.

Anthony L. Wilson

Chairman, President, and Chief Executive Officer of Mississippi Power

Age 57

First elected in 2015. President of Mississippi Power since October 2015 and Chief Executive Officer and Director since January 2016. Chairman of Mississippi Power's Board of Directors since August 2016.

Christopher C. Womack

Chairman, President, and Chief Executive Officer of Georgia Power

Age 63

First elected in 2008. Chairman and Chief Executive Officer of Georgia Power since June 2021 and President of Georgia Power since November 2020. Previously served as Executive Vice President and President of External Affairs of Southern Company from January 2009 to October 2020.

The officers of Southern Company were elected pursuant to a written consent in lieu of a meeting of the directors following the last annual meeting of stockholders held on May 26, 2021 for a term of one year or until their successors are elected and have qualified, except for Mr. Tucker, whose election as Executive Vice President and Chief Financial Officer of Southern Company was effective September 1, 2021.

I-36

Table of Contents Index to Financial Statements

INFORMATION ABOUT OUR EXECUTIVE OFFICERS – ALABAMA POWER

(Identification of executive officers of Alabama Power is inserted in Part I in accordance with Regulation S-K, Item 401.) The ages of the officers set forth below are as of December 31, 2021.

Mark A. Crosswhite

Chairman, President, and Chief Executive Officer

Age 59

First elected in 2014. President, Chief Executive Officer, and Director since March 1, 2014. Chairman since May 2014.

J. Jeffrey Peoples

Executive Vice President

Age 62

First elected in 2020. Executive Vice President of Customer and Employee Services since June 2020. Previously served as Senior Vice President of Employee Services and Labor Relations from June 2018 to June 2020 and as Vice President of Human Resources from December 2015 to June 2018.

Philip C. Raymond

Executive Vice President, Chief Financial Officer, and Treasurer

Age 62

First elected in 2010. Executive Vice President, Chief Financial Officer, and Treasurer since August 2010.

Zeke W. Smith

Executive Vice President

Age 62

First elected in 2010. Executive Vice President of External Affairs since November 2010.

James P. Heilbron

Senior Vice President and Senior Production Officer

Age 50

First elected in 2013. Senior Vice President and Senior Production Officer of Alabama Power since March 2013 and Senior Vice President and Senior Production Officer – West of SCS and Senior Production Officer of Mississippi Power since October 2018.

R. Scott Moore

Senior Vice President

Age 54

First elected in 2017. Senior Vice President of Power Delivery since May 2017. Previously served as Vice President of Transmission from August 2012 to May 2017.

The officers of Alabama Power were elected at the meeting of the directors held on April 23, 2021 for a term of one year or until their successors are elected and have qualified.

I-37

Table of Contents Index to Financial Statements

PART II

(a)(1) The common stock of Southern Company is listed and traded on the NYSE under the ticker symbol SO. The common stock is also traded on regional exchanges across the U.S.

There is no market for the other Registrants' common stock, all of which is owned by Southern Company.

(a)(2) Number of Southern Company's common stockholders of record at January 31, 2022: 103,154

Southern Company has paid dividends on its common stock since 1948. Dividends paid per share of common stock were $2.62 in 2021 and $2.54 in 2020. In January 2022, Southern Company declared a quarterly dividend of 66 cents per share. Dividends on Southern Company's common stock are payable at the discretion of Southern Company's Board of Directors and depend upon earnings, financial condition, and other factors. See Note 8 to the financial statements under "Dividend Restrictions" in Item 8 herein for additional information.

Each of the other Registrants have one common stockholder, Southern Company.

(a)(3) Securities authorized for issuance under equity compensation plans.

See Part III, Item 12. Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters.

(b) Use of Proceeds

Not applicable.

(c) Issuer Purchases of Equity Securities

None.

II-1

Table of Contents Index to Financial Statements

This section generally discusses 2021 and 2020 items and year-to-year comparisons between 2021 and 2020. Discussions of 2019 items and year-to-year comparisons between 2020 and 2019 that are not included in this Annual Report on Form 10-K can be found in Item 7 of each Registrant's Annual Report on Form 10-K for the year ended December 31, 2020, which was filed with the SEC on February 17, 2021. The following Management's Discussion and Analysis of Financial Condition and Results of Operations is a combined presentation; however, information contained herein relating to any individual Registrant is filed by such Registrant on its own behalf and each Registrant makes no representation as to information related to the other Registrants.

See MANAGEMENT'S DISCUSSION AND ANALYSIS – FINANCIAL CONDITION AND LIQUIDITY – "Market Price Risk" in Item 7 herein and Note 1 to the financial statements under "Financial Instruments" in Item 8 herein. Also see Notes 13 and 14 to the financial statements in Item 8 herein.

II-2

Table of Contents Index to Financial Statements

COMBINED MANAGEMENT'S DISCUSSION AND ANALYSIS

Southern Company and Subsidiary Companies 2021 Annual Report

OVERVIEW

Business Activities

Southern Company is a holding company that owns all of the common stock of three traditional electric operating companies, Southern Power, and Southern Company Gas and owns other direct and indirect subsidiaries. The primary businesses of the Southern Company system are electricity sales by the traditional electric operating companies and Southern Power and the distribution of natural gas by Southern Company Gas. Southern Company's reportable segments are the sale of electricity by the traditional electric operating companies, the sale of electricity in the competitive wholesale market by Southern Power, and the sale of natural gas and other complementary products and services by Southern Company Gas. See Note 16 to the financial statements for additional information.

• The traditional electric operating companies – Alabama Power, Georgia Power, and Mississippi Power – are vertically integrated utilities providing electric service to retail customers in three Southeastern states in addition to wholesale customers in the Southeast.

• Southern Power develops, constructs, acquires, owns, and manages power generation assets, including renewable energy projects, and sells electricity at market-based rates in the wholesale market. Southern Power continually seeks opportunities to execute its strategy to create value through various transactions including acquisitions, dispositions, and sales of partnership interests, development and construction of new generating facilities, and entry into PPAs primarily with investor-owned utilities, IPPs, municipalities, electric cooperatives, and other load-serving entities, as well as commercial and industrial customers. In general, Southern Power commits to the construction or acquisition of new generating capacity only after entering into or assuming long-term PPAs for the new facilities.

• Southern Company Gas is an energy services holding company whose primary business is the distribution of natural gas. Southern Company Gas owns natural gas distribution utilities in four states – Illinois, Georgia, Virginia, and Tennessee – and is also involved in several other complementary businesses. Southern Company Gas manages its business through three reportable segments – gas distribution operations, gas pipeline investments, and gas marketing services, which includes SouthStar, a Marketer and provider of energy-related products and services to natural gas markets – and one non-reportable segment, all other. Prior to the sale of Sequent on July 1, 2021, Southern Company Gas' reportable segments also included wholesale gas services. See Notes 7, 15, and 16 to the financial statements for additional information.

Southern Company's other business activities include providing distributed energy and resilience solutions and deploying microgrids for commercial, industrial, governmental, and utility customers, as well as investments in telecommunications and gas storage facilities. Management continues to evaluate the contribution of each of these activities to total shareholder return and may pursue acquisitions, dispositions, and other strategic ventures or investments accordingly.

See FUTURE EARNINGS POTENTIAL herein for a discussion of the many factors that could impact the Registrants' future results of operations, financial condition, and liquidity.

Recent Developments

Southern Company

On October 29, 2021, Southern Company completed the sale of assets subject to a domestic leveraged lease to the lessee for $45 million. No gain or loss was recognized on the sale. On December 13, 2021, Southern Company completed the termination of its leasehold interest in assets associated with its two international leveraged lease projects and received cash proceeds of approximately $673 million after the accelerated exercise of the lessee's purchase options. The pre-tax gain associated with the transaction was approximately $93 million ($99 million gain after tax). See Note 15 to the financial statements under "Southern Company" for additional information.

Alabama Power

On September 23, 2021, Alabama Power entered into an agreement to acquire all of the equity interests in Calhoun Power Company, LLC, which owns and operates a 743-MW winter peak, simple-cycle, combustion turbine generation facility in Calhoun County, Alabama (Calhoun Generating Station). The completion of the acquisition is subject to the satisfaction and waiver of certain conditions, including, among other customary conditions, approval by the Alabama PSC and the FERC. On October 28, 2021, Alabama Power filed a petition for a CCN with the Alabama PSC to procure additional generating capacity through this acquisition. The ultimate outcome of this matter cannot be determined at this time.

II-3

Table of Contents Index to Financial Statements

COMBINED MANAGEMENT'S DISCUSSION AND ANALYSIS (continued)

Southern Company and Subsidiary Companies 2021 Annual Report

During 2021, Alabama Power continued construction of Plant Barry Unit 8. At December 31, 2021, associated project expenditures included in CWIP totaled approximately $304 million.

For the year ended December 31, 2021, Alabama Power's weighted common equity return exceeded 6.15%, resulting in Alabama Power establishing a current regulatory liability of $181 million. In accordance with an Alabama PSC order issued on February 1, 2022, Alabama Power will apply $126 million to reduce the Rate ECR under recovered balance and the remaining $55 million will be refunded to customers through bill credits in July 2022.

See Note 2 to the financial statements under "Alabama Power" for additional information.

Georgia Power

Plant Vogtle Units 3 and 4 Construction and Start-Up Status

Construction continues on Plant Vogtle Units 3 and 4 (with electric generating capacity of approximately 1,100 MWs each), in which Georgia Power holds a 45.7% ownership interest. Georgia Power's share of the total project capital cost forecast to complete Plant Vogtle Units 3 and 4, including contingency, through the end of the first quarter 2023 and the fourth quarter 2023, respectively, is $10.4 billion.

Georgia Power estimates the productivity impacts of the COVID-19 pandemic have consumed approximately three to four months of schedule margin previously embedded in the site work plan for Unit 3 and Unit 4. The continuing effects of the COVID-19 pandemic could further disrupt or delay construction and testing activities at Plant Vogtle Units 3 and 4.

During 2021, Southern Nuclear performed additional construction remediation work necessary to ensure quality and design standards are met and support system turnovers necessary for Unit 3 hot functional testing, which was completed in July 2021, and fuel load. As a result of Unit 3 challenges including, but not limited to, construction productivity, construction remediation work, the pace of system turnovers, spent fuel pool repairs, and the timeframe and duration for hot functional and other testing, at the end of each of the second and third quarters 2021, Southern Nuclear further extended certain milestone dates, including fuel load for Unit 3, from those established in January 2021. Through the fourth quarter 2021, the project continued to face these and other challenges related to the completion of documentation, inclu

Showing the first 8K of 339K characters. Open the full section

Showing the first 8K of 936K characters. Open the full section

None.

Disclosure Controls and Procedures.

As of the end of the period covered by this Annual Report on Form 10-K, Southern Company, Alabama Power, Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas conducted separate evaluations under the supervision and with the participation of each company's management, including the Chief Executive Officer and Chief Financial Officer, of the effectiveness of the design and operation of the disclosure controls and procedures (as defined in Rules 13a-15(e) and 15d-15(e) of the Securities Exchange Act of 1934, as amended). Based upon these evaluations, the Chief Executive Officer and the Chief Financial Officer, in each case, concluded that the disclosure controls and procedures are effective.

Internal Control Over Financial Reporting.

(a) Management's Annual Report on Internal Control Over Financial Reporting.

(b) Attestation Report of the Registered Public Accounting Firm.

The report of Deloitte & Touche LLP, Southern Company's independent registered public accounting firm, regarding Southern Company's Internal Control over Financial Reporting is included in Item 8 herein of this Form 10-K. This report is not applicable to Alabama Power, Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas as these companies are not accelerated filers or large accelerated filers.

(c) Changes in internal control over financial reporting.

There have been no changes in Southern Company's, Alabama Power's, Georgia Power's, Mississippi Power's, Southern Power's, or Southern Company Gas' internal control over financial reporting (as such term is defined in Rules 13a-15(f) and 15d-15(f) under the Securities Exchange Act of 1934, as amended) during the fourth quarter 2021 that have materially affected or are reasonably likely to materially affect Southern Company's, Alabama Power's, Georgia Power's, Mississippi Power's, Southern Power's, or Southern Company Gas' internal control over financial reporting.

None.

Not applicable.

II-269

Table of Contents Index to Financial Statements

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Southern Company and Subsidiary Companies 2021 Annual Report

The management of Southern Company is responsible for establishing and maintaining an adequate system of internal control over financial reporting as required by the Sarbanes-Oxley Act of 2002 and as defined in Exchange Act Rule 13a-15(f). A control system can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

Under management's supervision, an evaluation of the design and effectiveness of Southern Company's internal control over financial reporting was conducted based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that Southern Company's internal control over financial reporting was effective as of December 31, 2021.

Deloitte & Touche LLP, as auditors of Southern Company's financial statements, has issued an attestation report on the effectiveness of Southern Company's internal control over financial reporting as of December 31, 2021, which is included herein.

/s/ Thomas A. Fanning

Thomas A. Fanning

Chairman, President, and Chief Executive Officer

/s/ Daniel S. Tucker

Daniel S. Tucker

Executive Vice President and Chief Financial Officer

February 16, 2022

II-270

Table of Contents Index to Financial Statements

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Alabama Power Company 2021 Annual Report

The management of Alabama Power is responsible for establishing and maintaining an adequate system of internal control over financial reporting as required by the Sarbanes-Oxley Act of 2002 and as defined in Exchange Act Rule 13a-15(f). A control system can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

Under management's supervision, an evaluation of the design and effectiveness of Alabama Power's internal control over financial reporting was conducted based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that Alabama Power's internal control over financial reporting was effective as of December 31, 2021.

/s/ Mark A. Crosswhite

Mark A. Crosswhite

Chairman, President, and Chief Executive Officer

/s/ Philip C. Raymond

Philip C. Raymond

Executive Vice President, Chief Financial Officer, and Treasurer

February 16, 2022

II-271

Table of Contents Index to Financial Statements

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Georgia Power Company 2021 Annual Report

The management of Georgia Power is responsible for establishing and maintaining an adequate system of internal control over financial reporting as required by the Sarbanes-Oxley Act of 2002 and as defined in Exchange Act Rule 13a-15(f). A control system can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

Under management's supervision, an evaluation of the design and effectiveness of Georgia Power's internal control over financial reporting was conducted based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that Georgia Power's internal control over financial reporting was effective as of December 31, 2021.

/s/ Christopher C. Womack

Christopher C. Womack

Chairman, President, and Chief Executive Officer

/s/ Aaron P. Abramovitz

Aaron P. Abramovitz

Executive Vice President, Chief Financial Officer, and Treasurer

February 16, 2022

II-272

Table of Contents Index to Financial Statements

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Mississippi Power Company 2021 Annual Report

The management of Mississippi Power is responsible for establishing and maintaining an adequate system of internal control over financial reporting as required by the Sarbanes-Oxley Act of 2002 and as defined in Exchange Act Rule 13a-15(f). A control system can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

Under management's supervision, an evaluation of the design and effectiveness of Mississippi Power's internal control over financial reporting was conducted based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that Mississippi Power's internal control over financial reporting was effective as of December 31, 2021.

/s/ Anthony L. Wilson

Anthony L. Wilson

Chairman, President, and Chief Executive Officer

/s/ Moses H. Feagin

Moses H. Feagin

Senior Vice President, Chief Financial Officer, and Treasurer

February 16, 2022

II-273

Table of Contents Index to Financial Statements

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Southern Power Company and Subsidiary Companies 2021 Annual Report

The management of Southern Power is responsible for establishing and maintaining an adequate system of internal control over financial reporting as required by the Sarbanes-Oxley Act of 2002 and as defined in Exchange Act Rule 13a-15(f). A control system can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

Under management's supervision, an evaluation of the design and effectiveness of Southern Power's internal control over financial reporting was conducted based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that Southern Power's internal control over financial reporting was effective as of December 31, 2021.

/s/ Christopher Cummiskey

Christopher Cummiskey

Chairman and Chief Executive Officer

/s/ Elliott L. Spencer

Elliott L. Spencer

Senior Vice President, Chief Financial Officer, and Treasurer

February 16, 2022

II-274

Table of Contents Index to Financial Statements

MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Southern Company Gas and Subsidiary Companies 2021 Annual Report

The management of Southern Company Gas is responsible for establishing and maintaining an adequate system of internal control over financial reporting as required by the Sarbanes-Oxley Act of 2002 and as defined in Exchange Act Rule 13a-15(f). A control system can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

Under management's supervision, an evaluation of the design and effectiveness of Southern Company Gas' internal control over financial reporting was conducted based on the framework in Internal Control—Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that Southern Company Gas' internal control over financial reporting was effective as of December 31, 2021.

/s/ Kimberly S. Greene

Kimberly S. Greene

Chairman, President, and Chief Executive Officer

/s/ David P. Poroch

David P. Poroch

Executive Vice President, Chief Financial Officer, and Treasurer

February 16, 2022

II-275

Table of Contents Index to Financial Statements

PART III

Items 10 (other than the information under "Code of Ethics" below), 11, 12, 13, and 14 for Southern Company are incorporated by reference to Southern Company's Definitive Proxy Statement relating to the 2022 Annual Meeting of Stockholders. Specifically, reference is made to "Corporate Governance at Southern Company" and "Biographical Information about our Nominees for Director," as well as "Delinquent Section 16(a) Reports," if required, for Item 10, "Compensation Discussion and Analysis," "Executive Compensation Tables," and "Director Compensation" for Item 11, "Stock Ownership Information," "Executive Compensation Tables," and "Equity Compensation Plan Information" for Item 12, "Biographical Information about our Nominees for Director" and "Corporate Governance at Southern Company" for Item 13, and "Principal Independent Registered Public Accounting Firm Fees" for Item 14.

Items 10 (other than the information under "Code of Ethics" below), 11, 12, 13, and 14 for Alabama Power are incorporated by reference to Alabama Power's Definitive Proxy Statement relating to its 2022 Annual Meeting of Shareholders. Specifically, reference is made to "Nominees for Election as Directors," "Corporate Governance," and "Delinquent Section 16(a) Reports," if required, for Item 10, "Executive Compensation," "Compensation Committee Interlocks and Insider Participation," "Director Compensation," "Director Deferred Compensation Plan," and "Director Compensation Table" for Item 11, "Stock Ownership Table" and "Executive Compensation" for Item 12, "Certain Relationships and Related Transactions" and "Governance Policies and Processes and Director Independence" for Item 13, and "Principal Independent Registered Public Accounting Firm Fees" for Item 14.

Items 10, 11, 12, and 13 for each of Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas are omitted pursuant to General Instruction I(2)(c) of Form 10-K. Item 14 for each of Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas is contained herein.

Code of Ethics

The Registrants collectively have adopted a code of business conduct and ethics (Code of Ethics) that applies to each director, officer, and employee of the Registrants and their subsidiaries. The Code of Ethics can be found on Southern Company's website located at www.southerncompany.com. The Code of Ethics is also available free of charge in print to any shareholder by requesting a copy from Myra C. Bierria, Corporate Secretary, Southern Company, 30 Ivan Allen Jr. Boulevard NW, Atlanta, Georgia 30308. Any amendment to or waiver from the Code of Ethics that applies to executive officers and directors will be posted on the website.

III-1

Table of Contents Index to Financial Statements

The following represents fees billed to Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas in 2021 and 2020 by Deloitte & Touche LLP, each company's principal public accountant:

(1)Includes services performed in connection with financing transactions.

(2)Represents fees for non-statutory audit services and audit services associated with reviewing internal controls for a system implementation.

(3)Represents registration fees for attendance at Deloitte & Touche LLP-sponsored education seminars in 2021 and 2020 and other advisory services in 2021.

(4)Represents fees in connection with audits of Southern Power partnerships in 2021 and 2020, audit services associated with green bond expenditures in 2021, and audit services associated with reviewing internal controls for a system implementation in 2020.

(5)Includes fees in connection with statutory audits of several Southern Company Gas subsidiaries.

(6)Represents fees for non-statutory audit services and audit services associated with reviewing internal controls for a system implementation in 2021 and 2020 and audit services associated with a forecast review in 2021.

The Southern Company Audit Committee (on behalf of Southern Company and its subsidiaries) has a Policy of Engagement of the Independent Auditor for Audit and Non-Audit Services that includes pre-approval requirements for the audit and non-audit services provided by Deloitte & Touche LLP. All of the services provided by Deloitte & Touche LLP in fiscal years 2021 and 2020 and related fees were approved in advance by the Southern Company Audit Committee.

III-2

Table of Contents Index to Financial Statements

PART IV

(a)The following documents are filed as a part of this report on Form 10-K:

(1)Financial Statements and Financial Statement Schedules:

Management's Reports on Internal Control Over Financial Reporting for Southern Company and Subsidiary Companies, Alabama Power, Georgia Power, Mississippi Power, Southern Power and Subsidiary Companies, and Southern Company Gas and Subsidiary Companies are listed under Item 9A herein.

Reports of Independent Registered Public Accounting Firm (Deloitte & Touche LLP, PCAOB ID: 34) on the financial statements for Southern Company and Subsidiary Companies, Alabama Power Company, Georgia Power Company, Mississippi Power Company, Southern Power Company and Subsidiary Companies, and Southern Company Gas and Subsidiary Companies are listed under Item 8 herein. Also included in Item 8 herein is the Report of Independent Registered Public Accounting Firm (BDO USA, LLP; Houston, Texas; PCAOB ID: 243) on the financial statements of Southern Natural Gas Company, L.L.C., Southern Company Gas' investment which is accounted for by the use of the equity method.

The financial statements filed as a part of this report for Southern Company and Subsidiary Companies, Alabama Power, Georgia Power, Mississippi Power, Southern Power and Subsidiary Companies, and Southern Company Gas and Subsidiary Companies are listed under Item 8 herein.

Reports of Independent Registered Public Accounting Firm (Deloitte & Touche LLP, PCAOB ID 34) on the financial statement schedules for Southern Company and Subsidiary Companies, Alabama Power Company, Georgia Power Company, Mississippi Power Company, Southern Power Company and Subsidiary Companies, and Southern Company Gas and Subsidiary Companies are included on pages IV-2 through IV-7.

The financial statement schedules (Schedule II, Valuation and Qualifying Accounts and Reserves) for Southern Company and Subsidiary Companies, Alabama Power, Georgia Power, Mississippi Power, Southern Power and Subsidiary Companies, and Southern Company Gas and Subsidiary Companies are included on pages page IV-8 and IV-9. Columns in Schedule II may be omitted if the information is not applicable or not required. All other schedules are omitted as not applicable or not required.

(2)Exhibits:

Exhibits for Southern Company, Alabama Power, Georgia Power, Mississippi Power, Southern Power, and Southern Company Gas are listed in the Exhibit Index at page E-1.

None.

IV-1

Table of Contents Index to Financial Statements

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the stockholders and the Board of Directors of The Southern Company and Subsidiary Companies

Opinion on the Financial Statement Schedule

We have audited the consolidated financial statements of The Southern Company and subsidiary companies (Southern Company) as of December 31, 2021 and 2020, and for each of the three years in the period ended December 31, 2021, and Southern Company's internal control over financial reporting as of December 31, 2021, and have issued our report thereon dated February 16, 2022; such report is included elsewhere in this Form 10-K. Our audits also included the financial statement schedule of Southern Company listed in Item 15. This financial statement schedule is the responsibility of Southern Company's management. Our responsibility is to express an opinion based on our audits. In our opinion, such financial statement schedule, when considered in relation to the financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

/s/ Deloitte & Touche LLP

Atlanta, Georgia

February 16, 2022

IV-2

Table of Contents Index to Financial Statements

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the stockholders and the Board of Directors of Alabama Power Company

Opinion on the Financial Statement Schedule

We have audited the financial statements of Alabama Power Company (Alabama Power) (a wholly-owned subsidiary of The Southern Company) as of December 31, 2021 and 2020, and for each of the three years in the period ended December 31, 2021, and have issued our report thereon dated February 16, 2022; such report is included elsewhere in this Form 10-K. Our audits also included the financial statement schedule of Alabama Power listed in Item 15. This financial statement schedule is the responsibility of Alabama Power's management. Our responsibility is to express an opinion based on our audits. In our opinion, such financial statement schedule, when considered in relation to the financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

/s/ Deloitte & Touche LLP

Birmingham, Alabama

February 16, 2022

IV-3

Table of Contents Index to Financial Statements

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the stockholder and the Board of Directors of Georgia Power Company

Opinion on the Financial Statement Schedule

We have audited the financial statements of Georgia Power Company (Georgia Power) (a wholly-owned subsidiary of The Southern Company) as of December 31, 2021 and 2020, and for each of the three years in the period ended December 31, 2021, and have issued our report thereon dated February 16, 2022; such report is included elsewhere in this Form 10-K. Our audits also included the financial statement schedule of Georgia Power listed in Item 15. This financial statement schedule is the responsibility of Georgia Power's management. Our responsibility is to express an opinion based on our audits. In our opinion, such financial statement schedule, when considered in relation to the financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

/s/ Deloitte & Touche LLP

Atlanta, Georgia

February 16, 2022

IV-4

Table of Contents Index to Financial Statements

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the stockholders and the Board of Directors of Mississippi Power Company

Opinion on the Financial Statement Schedule

We have audited the financial statements of Mississippi Power Company (Mississippi Power) (a wholly-owned subsidiary of The Southern Company) as of December 31, 2021 and 2020, and for each of the three years in the period ended December 31, 2021, and have issued our report thereon dated February 16, 2022; such report is included elsewhere in this Form 10-K. Our audits also included the financial statement schedule of Mississippi Power listed in Item 15. This financial statement schedule is the responsibility of Mississippi Power's management. Our responsibility is to express an opinion based on our audits. In our opinion, such financial statement schedule, when considered in relation to the financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

/s/ Deloitte & Touche LLP

Atlanta, Georgia

February 16, 2022

IV-5

Table of Contents Index to Financial Statements

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the stockholder and the Board of Directors of Southern Power Company and Subsidiary Companies

Opinion on the Financial Statement Schedule

We have audited the consolidated financial statements of Southern Power Company and subsidiary companies (Southern Power) (a wholly-owned subsidiary of The Southern Company) as of December 31, 2021 and 2020, and for each of the three years in the period ended December 31, 2021, and have issued our report thereon dated February 16, 2022; such report is included elsewhere in this Form 10-K. Our audits also included the financial statement schedule of Southern Power listed in Item 15. This financial statement schedule is the responsibility of Southern Power's management. Our responsibility is to express an opinion based on our audits. In our opinion, such financial statement schedule, when considered in relation to the financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

/s/ Deloitte & Touche LLP

Atlanta, Georgia

February 16, 2022

IV-6

Table of Contents Index to Financial Statements

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the stockholder and the Board of Directors of Southern Company Gas and Subsidiary Companies

Opinion on the Financial Statement Schedule

We have audited the consolidated financial statements of Southern Company Gas and subsidiary companies (Southern Company Gas) (a wholly-owned subsidiary of The Southern Company) as of December 31, 2021 and 2020, and for each of the three years in the period ended December 31, 2021, and have issued our report thereon dated February 16, 2022; such report is included elsewhere in this Form 10-K. Our audits also included the financial statement schedule of Southern Company Gas listed in Item 15. This financial statement schedule is the responsibility of Southern Company Gas' management. Our responsibility is to express an opinion based on our audits. In our opinion, such financial statement schedule, when considered in relation to the financial statements taken as a whole, presents fairly, in all material respects, the information set forth therein.

/s/ Deloitte & Touche LLP

Atlanta, Georgia

February 16, 2022

IV-7

Table of Contents Index to Financial Statements

SCHEDULE II — VALUATION AND QUALIFYING ACCOUNTS

FOR THE YEARS ENDED DECEMBER 31, 2021, 2020, AND 2019

Showing the first 8K of 137K characters. Open the full section