Southern Company 10-K 2023-12-31

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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, 2023

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

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

Securities registered pursuant to Section 12(g) of the Act: None

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 ¨

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. ☐

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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.

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant's executive officers during the relevant recovery period pursuant to § 240.10D-1(b). ☐

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, 2023: $76.6 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 2024 Annual Meeting of Stockholders are incorporated by reference into PART III.

Each of Alabama Power Company, 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.

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DEFINITIONS

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

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DEFINITIONS

(continued)

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DEFINITIONS

(continued)

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DEFINITIONS

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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 regulated rates, the strategic goals for the business, customer and sales growth, economic conditions, including inflation, 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, 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 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 and Plant Vogtle Units 3 and 4;

• 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 and commodities;

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

• transmission constraints;

• 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 Unit 4 (which includes components based on new technology that only within the last several years began initial operation in the global nuclear industry at this scale), due to current and/or future challenges which include, but are not limited to, changes in labor costs, availability, and productivity; challenges with the 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; the impacts of inflation; 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; challenges with start-up activities, including major equipment failure, or system integration; and/or operational performance; challenges related to pandemic health events; continued public and policymaker support for projects; environmental and geological conditions; delays or increased costs to interconnect facilities to transmission grids; and increased financing costs as a result of changes in interest rates or as a result of project delays;

• the ability to overcome or mitigate the current challenges, or challenges yet to be identified, at Plant Vogtle Unit 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 past and ongoing construction projects, including PSC approvals and FERC actions;

• under certain specified circumstances, a decision by holders of more than 10% of the ownership interests of Plant Vogtle Unit 4 not to proceed with construction;

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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 and battery energy storage 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 traditional electric operating companies' and SEGCO's generation, 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 cyber and physical attacks;

• global and U.S. economic conditions, including impacts from geopolitical conflicts, recession, inflation, 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 ability of the traditional electric operating companies 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, wars, 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.

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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 of the Subsidiary Registrants, 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 122,000 square miles in the Southeast. Southern Holdings is an intermediate holding company subsidiary, which invests in various projects. Southern Nuclear operates and provides services to the Southern Company system's nuclear power plants and is currently managing construction and start-up of Plant Vogtle Unit 4, which is 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. Alabama Power, Georgia Power, and Mississippi Power each operate with one reportable business segment, since substantially all of their business is providing electric service to customers. Southern Power also operates its business with one reportable business segment, the sale of electricity in the competitive wholesale market.

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

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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 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 November 2022, the Southeast Energy Exchange Market (SEEM) began service. SEEM, whose members include the traditional electric operating companies and many of the other electric service providers in the Southeast, is an extension of the existing bilateral market where participants use an automated, intra-hour energy exchange to buy and sell power close to the time the energy is consumed, utilizing available unreserved transmission. On July 14, 2023, the U.S. Court of Appeals for the District of Columbia Circuit vacated certain FERC orders related to SEEM and remanded the proceeding to the FERC. 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 p

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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 retail customers, 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 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. The outcome of any such proceeding could be impacted by a variety of factors, including the level of opposition from intervenors, potential impacts to customers, and past or future changes in the political, regulatory, economic, or legislative environment. 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 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 costs are recovered through wholesale electric tariffs, the majority are recovered through retail rates. Transmission planning and the resulting grid improvements could be impacted by FERC policy changes as well as North American Electric Reliability Corporation planning standard changes.

The IRA, among other items, imposes a 15% corporate minimum tax on book income and is subject to the issuance of additional guidance by the U.S. Treasury Department and the IRS. Any rate recovery by the traditional electric operating companies or the natural gas distribution utilities will be determined pursuant to the regulatory processes of the FERC, state PSCs, or other applicable state regulatory agencies. There is no assurance, however, that such tax expense will be recoverable through the applicable regulatory process.

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 application of existing regulations and 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 under the Resource Conservation and Recovery Act and applicable state laws. The cost estimates for AROs related to the disposal of CCR are based on information using various assumptions

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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 and those updates could be material.

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 United States. This litigation has included, but is not limited to, 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 adv

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None.

Cybersecurity is a critical component of Southern Company's risk management program. The Southern Company system has implemented a cybersecurity program to assess, identify, and manage risks from cybersecurity threats that may result in material adverse effects on the Southern Company system's ability to fulfill critical business functions, including energy delivery service failures, and on the confidentiality, integrity, and availability of the Southern Company system's information systems.

Governance and Oversight of Cybersecurity Risk

Board of Directors

The Southern Company Board of Directors (Board), along with certain committees (primarily the Audit Committee of the Board) oversees the Southern Company system's enterprise risk management process. The Board devotes significant time and attention to overseeing cybersecurity risk, and the Southern Company system's approach to cybersecurity governance establishes oversight throughout the enterprise. The Board has delegated the primary responsibility to oversee cybersecurity matters to the Business Security and Resiliency Committee (BSRC) of the Board. Having a committee like the BSRC, focused on and dedicated to security, is a strong governance practice. Comprised solely of independent members of the Board, the BSRC is charged with oversight of risks related to cybersecurity, physical security, and operational resiliency. The BSRC

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includes directors with an understanding of cyber issues. The BSRC meets at every regular Board meeting and when needed in the event of a specific threat or emerging issue. The Chair of the BSRC regularly reports to the Board in connection with key matters the BSRC considered. The BSRC routinely receives presentations on a range of topics, including the threat environment and vulnerabilities and risks, policies, practices, technology trends, and regulatory developments, from the Chief Information Security Officer (CISO) and the legal organization and, as needed, the Chief Information Officer (CIO). The CISO reports to the BSRC at each regular committee meeting. Protocols have been established by which certain cybersecurity incidents are escalated internally and, where appropriate, reported to the BSRC, and ongoing updates regarding any such incident are provided until it has been resolved. See "Incident Response" herein.

Management

The Southern Company system has implemented a cross-functional, risk-based, "defense-in-depth" approach to preventing, detecting, identifying, mitigating, responding to, and recovering from cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents so that decisions regarding the public disclosure and reporting of such incidents can be made by management in a timely manner. Overall network efforts are led by the CISO and the Technology Security Organization (TSO), the organization responsible for implementing, monitoring, and maintaining cybersecurity practices across the Southern Company system, and aided by the Executive Vice President of Operations and the Energy Management System and Generation organization. The CISO meets regularly with the CIO and the Chief Executive Officer and reports regularly to committees of the Board to discuss risk management measures implemented to identify and mitigate data protection and cybersecurity risks. Security and resiliency are emphasized through business assurance, enterprise risk management, and incident response plans designed to identify, evaluate, and remediate incidents when they occur. Among other things, the Cybersecurity Incident Response Plan (CIRP) establishes a team comprised of the CISO, the Deputy CISO, the Director of the Digital Defense Center, and members of the legal and compliance organizations to evaluate emerging cyber threats and escalate to executive management and business units as appropriate. Plans, policies, and technologies are regularly updated and training exercises and crisis management preparedness activities are conducted to test effectiveness.

The CISO works closely with the legal and compliance organizations, as well as the relevant business units, to help ensure broad oversight of and compliance with legal, regulatory, and contractual cybersecurity requirements. The CISO has extensive cybersecurity knowledge and skills gained from over 30 years of work experience within the Southern Company system. The CISO receives reports on cybersecurity threats from a variety of sources both internally and externally on an ongoing basis and regularly reviews risk management measures implemented to identify and mitigate cybersecurity risks. Briefings to the Board on cybersecurity matters include annual briefings to the Audit Committee and the Operations, Environmental, and Safety Committee in addition to briefings to the BSRC at each of its regular meetings (at least five times annually).

Internal Cybersecurity Team

The TSO, led by the CISO, is responsible for the implementation, monitoring, and maintenance of the cybersecurity and data protection practices across the Southern Company system. The Southern Company system also relies on a Data Privacy and Protection team in the compliance organization, as well as the internal audit organization, to work with the TSO on data protection policies and practices. Multiple experienced information security leaders with internal and external security experience responsible for various parts of the business report to the CISO, each of whom is supported by a team of trained cybersecurity professionals. In addition to these internal cybersecurity capabilities, external auditors and security companies are regularly engaged to assist with assessing, testing, identifying, and managing cybersecurity, including through penetration testing, vulnerability testing, and other technical evaluations.

Risk Management and Strategy

Although many of the networks are segmented, overall network security is a centralized shared service across the Southern Company system, led by the TSO and the CISO. Recognizing that no single technology, process, or business control can effectively prevent or mitigate all risks related to cyber threats, multiple technologies, processes, and controls, all working independently but as part of a cohesive strategy, are employed to reduce risk. Southern Company system exposure and defenses are regularly tested through auditing, penetration testing, vulnerability testing, and other exercises designed to assess effectiveness.

The Southern Company system emphasizes both security and resiliency through business assurance and incident response plans designed to identify, evaluate, and remediate incidents when they occur. A 24/7 security operations center is also utilized, which facilitates real-time situational awareness across the cyber-threat environment, and a robust insider threat protection program that leverages cross-function information sharing to assess insider threat activity is employed. The Southern Company system regularly reviews and updates its plans, policies, and technologies and conducts regular training exercises and crisis management preparedness activities to test their effectiveness. In addition, a security awareness program for the Southern

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Company system's employees has also been implemented, which is designed to educate and train employees at least annually, or more often as needed, about risks inherent to human interaction with information and operational technology.

The Southern Company system's cybersecurity program is increasingly leveraging intelligence-sharing capabilities about emerging threats within the energy industry, across other industries, with specialized vendors, and through public-private partnerships with U.S. government intelligence agencies. By engaging with both the Electricity Information Sharing and Analysis Center and the Downstream Natural Gas Information Sharing and Analysis Center, the Southern Company system benefits from quality analysis and rapid sharing of security information across the energy sector. Such intelligence helps to allow for better detection and prevention of emerging cyber threats before they materialize. Just as it tests its policies and plans internally, the Southern Company system also engages in external exercises such as the bi-annual GridEx Security Exercise to evaluate and address the preparedness of the industry as a whole.

Many cybersecurity policies and standards across the Southern Company system are governed by multiple regulatory requirements. Portions of these policies and standards are audited by the FERC, the Transportation Security Administration, and the NRC, as appropriate, and are periodically evaluated by third parties such as cybersecurity insurance carriers. Certain members of senior management have high-level security clearances to facilitate access to critical information, and the Southern Company system participates in pilot programs with industry and the U.S. government to share additional information and strengthen cybersecurity and business resiliency.

The Southern Company system also employs systems and processes designed to oversee, identify, and reduce the potential impact of a security incident at a third-party vendor, service provider, or customer or otherwise implicating the third-party technology and systems used. Among other things, the Southern Company system has established a Vendor Security Incident Working Group to address such third-party security incidents, including following up with the third party as appropriate and taking steps to mitigate any impact to systems. The Vendor Security Incident Working Group includes members of the internal cybersecurity teams to address any incidents that may invoke the CIRP. Additionally, the Southern Company system typically imposes contractual obligations on vendors and other third-party business partners related to privacy, confidentiality, and data security based on their access to the Southern Company system's data and systems. The Southern Company system also maintains insurance coverage for cyber incidents; the scope of coverage and fitness of coverage is evaluated each year.

Incident Response

The Southern Company system has adopted a CIRP that applies in the event of certain cybersecurity threats or incidents to provide a standardized guide for responding to security incidents. The CIRP sets out a coordinated approach to investigating, containing, documenting, and mitigating incidents, including reporting findings and keeping senior management and other key stakeholders informed and involved as appropriate. In general, the incident response process follows the National Institute of Standards and Technology guidance and focuses on four phases: preparation; detection and analysis; containment, eradication, and recovery; and post-incident remediation. The CIRP is reviewed periodically to help ensure its applicability to any changing needs or circumstances and to provide users a tactical tool to effectively respond to incidents. The CIRP applies to all Southern Company system personnel (including third-party contractors, vendors, and partners) that perform functions or services requiring access to secure Southern Company system information and to all devices and network services that are owned or managed by the Southern Company system. A full tabletop exercise is performed at least annually, including stakeholders from business units beyond technology security, such as power delivery, legal, compliance, risk management, and corporate communications. In addition, the Southern Company system participates in sector-level and cross-sector exercises led by industry or the U.S. government. In the event of an incident, the technology security organization, the legal organization, and other stakeholders frequently review lessons learned after an incident has been remediated.

Material Cybersecurity Risks, Threats, and Incidents

Due to evolving cybersecurity threats, it has and will continue to be difficult to prevent, detect, mitigate, and remediate cybersecurity incidents. Risks from cybersecurity threats, including as a result of any previous cybersecurity incidents, have not materially affected the Southern Company system, including its business strategy, results of operations, or financial condition. While the Southern Company system has not experienced any material cybersecurity incidents, there can be no guarantee that it will not be the subject of future successful attacks, threats, or incidents. Additional information on cybersecurity risks can be found in Item 1A "Risk Factors" of this Form 10-K which should be read in conjunction with the foregoing information.

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Electric

At December 31, 2023, the traditional electric operating companies, Southern Power, and SEGCO owned and/or operated the generating facilities listed 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.

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(a)Represents the primary fuel source.

(b)Operated by OPC.

(c)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.

(d)Southern Power is the controlling partner in a non-tax equity partnership for Beech Ridge II and also owns 100% of Glass Sands. Southern Power is the controlling partner in tax equity partnerships owning Cactus Flats, Deuel Harvest, Reading, Skookumchuck, and Wildhorse Mountain (additionally for Deuel Harvest and Skookumchuck, a noncontrolling interest in Southern Power's remaining equity is owned by another partner). Southern Power is the controlling partner in SP Wind (a tax equity partnership owning the remaining eight Southern Power wind facilities). SP Wind is the 90.1% majority owner of Wake Wind and owns 100% of the other SP Wind facilities. 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 owns a 67% equity interest in SP Solar (a limited partnership indirectly owning all of Southern Power's solar facilities, except the Gaskell West I and Roserock 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 is the controlling partner in a tax equity partnership owning Gaskell West I and also owns 100% of Roserock. 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.

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(f)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. 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.

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

(h)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.

See MANAGEMENT'S DISCUSSION AND ANALYSIS – FUTURE EARNINGS POTENTIAL – "Environmental Matters" in Item 7 herein and Note 2 to the financial statements under "Alabama Power – Environmental Accounting Order," "Georgia Power – Integrated Resource Plans," 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 covering all expenses and the amortization of the capitalized costs through the expiration of the agreement between the parties on May 31, 2024. At December 31, 2023, the unamortized portion was approximately $1 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 2019 sale of Gulf Power, Mississippi Power and NextEra Energy agreed to negotiate a mutually acceptable revised operating agreement for Plant Daniel. In July 2022, the co-owners executed a revised operating agreement. The dispatch procedures in the revised operating agreement for the two jointly-owned coal units at Plant Daniel resulted in Mississippi Power designating one of the two units as primary and the other as secondary in lieu of each company separately owning 100% of a single generating unit. Mississippi Power did not exercise an option to purchase its co-owner's ownership interest for $1 on January 15, 2024. See Notes 2 and 3 under "Mississippi Power – Integrated Resource Plan" and "Other Matters – Mississippi Power – Plant Daniel," respectively, in Item 8 herein for additional information on Plant Daniel.

In 2023, the maximum demand on the traditional electric operating companies, Southern Power Company, and SEGCO was 36,919,000 KWs and occurred on August 14, 2023. The all-time maximum demand of 37,035,000 KWs occurred on June 15, 2022. 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 2023 was 19%.

Jointly-Owned Facilities

Alabama Power, Georgia Power, and Mississippi Power at December 31, 2023 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:

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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.

In addition, Georgia Power has commitments, in the form of capacity purchases totaling $39 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 currently 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, 2023, Southern Company Gas' gas distribution operations segment owned approximately 77,900 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.

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All Other

In September 2022, certain affiliates of Southern Company Gas entered into agreements to sell two natural gas storage facilities located in California and Texas. The sale of the Texas facility was completed in November 2022 and the sale of the California facility was completed on September 22, 2023. See Note 15 to the financial statements under "Southern Company Gas" in Item 8 herein for additional information.

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. 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.

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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, 2023.

Christopher C. Womack

Chairman, President, and Chief Executive Officer

Age 65

First elected in 2008. President since March 2023, Chief Executive Officer since May 2023, and Chairman since December 2023. Previously served as Chairman and Chief Executive Officer of Georgia Power from June 2021 to March 2023, President of Georgia Power from November 2020 to March 2023, and Executive Vice President and President of External Affairs of Southern Company from January 2009 to October 2020.

Daniel S. Tucker

Executive Vice President and Chief Financial Officer

Age 53

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, and Executive Vice President and Chief Financial Officer of Southern Company Gas from January 2019 to January 2021.

Bryan D. Anderson

Executive Vice President

Age 57

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

Age 54

First elected in 2012. Executive Vice President since April 2021. Chairman, President, and Chief Executive Officer of SCS since April 2021. Previously served as Executive Vice President for Operations of SCS from June 2018 to April 2021.

Christopher Cummiskey

Executive Vice President

Age 49

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 60

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 Georgia Power

Age 57

First elected in 2013. Chairman, President, and Chief Executive Officer of Georgia Power since April 2023. Previously served as Chairman, President, and Chief Executive Officer of Southern Company Gas from June 2018 to March 2023.

James Y. Kerr II

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

Age 59

First elected in 2014. Chairman, President, and Chief Executive Officer of Southern Company Gas since April 2023. Previously served as Executive Vice President, Chief Legal Officer, and Chief Compliance Officer of Southern Company from March 2014 to March 2023.

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Stephen E. Kuczynski

Chairman and Chief Executive Officer of Southern Nuclear

Age 61

First elected in 2011. Chairman and Chief Executive Officer of Southern Nuclear since July 2011. Previously served as President of Southern Nuclear from July 2011 through March 2023.

J. Jeffrey Peoples

Chairman, President, and Chief Executive Officer of Alabama Power

Age 64

First elected in 2023. Chairman, President, and Chief Executive Officer of Alabama Power since January 2023. Previously served as Executive Vice President of Customer and Employee Services of Alabama Power from June 2020 to January 2023, Senior Vice President of Employee Services and Labor Relations of Alabama Power from June 2018 to June 2020, and Executive Vice President and Chief Administrative Officer of Southern Company Gas and President of AGL Services Company from September 2018 to June 2020.

Sterling A. Spainhour

Executive Vice President and Chief Legal Officer

Age 55

First elected in 2023. Executive Vice President and Chief Legal Officer since April 2023. Previously served as Chief Compliance Officer of Southern Company from April 2023 to January 2024, Senior Vice President, General Counsel, Corporate Secretary, and Chief Compliance Officer of Georgia Power from June 2020 to March 2023, Senior Vice President and General Counsel – East of SCS from July 2020 to March 2023, and Senior Vice President and General Counsel of SCS from December 2016 to July 2020.

Anthony L. Wilson

Chairman, President, and Chief Executive Officer of Mississippi Power

Age 59

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.

Each officer listed above was elected at the annual meeting (or by written consent in lieu of the annual meeting) of the board of directors of the applicable company, to serve until the next such annual meeting or until his or her successor is elected and qualified, except for Mr. Womack who was elected as Chairman on December 11, 2023.

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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, 2024: 95,412

Southern Company has paid dividends on its common stock since 1948. Dividends paid per share of common stock were $2.78 in 2023 and $2.70 in 2022. In January 2024, Southern Company declared a quarterly dividend of 70 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.

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This section generally discusses 2023 and 2022 items and year-to-year comparisons between 2023 and 2022. Discussions of 2021 items and year-to-year comparisons between 2022 and 2021 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, 2022, which was filed with the SEC on February 15, 2023. 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.

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COMBINED MANAGEMENT'S DISCUSSION AND ANALYSIS

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. 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 many factors that could impact the Registrants' future results of operations, financial condition, and liquidity.

Recent Developments

Alabama Power

On March 24, 2023, Alabama Power filed Rate CNP New Plant with the Alabama PSC to recover costs associated with the acquisition of the Central Alabama Generating Station. The filing reflected an annual increase in retail revenues of $78 million, or 1.1%, effective with June 2023 billings. Through May 2023, Alabama Power recovered substantially all costs associated with the Central Alabama Generating Station through Rate RSE, offset by revenues from a power sales agreement. On May 24, 2023, the Central Alabama Generating Station was placed into retail service. On November 1, 2023, Alabama Power placed Plant Barry Unit 8 in service. On December 1, 2023, Alabama Power filed Rate CNP New Plant with the Alabama PSC to recover costs associated with Plant Barry Unit 8. The filing reflected an annual increase in retail revenues of $91 million, or 1.4%, effective with January 2024 billings.

On June 14, 2023, the Alabama PSC issued an order approving modifications to Alabama Power's Renewable Generation Certificate. The modifications authorized Alabama Power to procure an additional 2,400 MWs of renewable capacity and energy by June 14, 2029 and to market the related energy and environmental attributes to customers and other third parties. The modifications also increased the size of allowable renewable projects from 80 MWs to 200 MWs and increased the annual approval limit from 160 MWs to 400 MWs.

On July 11, 2023, the Alabama PSC issued an order authorizing Alabama Power to expand the existing authority of its reliability reserve to include certain production-related expenses that are intended to maintain reliability in between scheduled generating unit maintenance outages.

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COMBINED MANAGEMENT'S DISCUSSION AND ANALYSIS

On August 18, 2023, Alabama Power notified the Alabama PSC of its intent to use a portion of its reliability reserve balance in 2023. During the fourth quarter 2023, Alabama Power used $75 million of the reliability reserve for reliability-related transmission, distribution, and generation expenses and nuclear production-related expenses. At December 31, 2023, Alabama Power accrued $52 million to its reliability reserve.

On October 3, 2023, the Alabama PSC issued an order modifying its December 2022 order related to excess federal accumulated deferred income taxes and authorizing Alabama Power to (i) flow back in 2023 approximately $24 million of certain federal excess accumulated deferred income taxes resulting from the Tax Cuts and Jobs Act of 2017 and (ii) make available any remaining balance of excess accumulated deferred income taxes at the end of 2023 for the benefit of customers in 2024 and/or 2025. At December 31, 2023, the remaining balance was $81 million, of which approximately $67 million and $14 million will flow back in 2024 and 2025, respectively, for the benefit of customers.

On November 9, 2023, the Alabama PSC approved a decrease to Rate ECR of approximately $126 million annually, effective with December 2023 billings.

On December 1, 2023, Alabama Power submitted calculations to the Alabama PSC for Rate CNP Compliance for 2024, which resulted in an annual revenue decrease of approximately $23 million, or 0.3%, effective with January 2024 billings.

For the year ended December 31, 2023, Alabama Power's weighted common equity return exceeded 6.15%, resulting in Alabama Power establishing a current regulatory liability of $15 million for Rate RSE refunds, which will be refunded to customers through bill credits in April 2024.

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

Georgia Power placed Plant Vogtle Unit 3 in service on July 31, 2023 and continues construction on Plant Vogtle Unit 4 (each with electric generating capacity of approximately 1,100 MWs), in which it holds a 45.7% ownership interest. Georgia Power's share of the total project capital cost forecast to complet

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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 2023 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.

There were no adoptions, modifications, or terminations of "Rule 10b5-1 trading arrangements" or "non-Rule 10b5-1 trading arrangements," as defined in Item 408(a) of Regulation S-K, during the three months ended December 31, 2023 by the Registrants' directors and "officers," as defined in Rule 16a-1(f) under the Securities Exchange Act of 1934, as amended.

Not applicable.

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MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Southern Company and Subsidiary Companies

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, 2023.

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, 2023, which is included herein.

/s/ Christopher C. Womack

Christopher C. Womack

Chairman, President, and Chief Executive Officer

/s/ Daniel S. Tucker

Daniel S. Tucker

Executive Vice President and Chief Financial Officer

February 14, 2024

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MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Alabama Power Company

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, 2023.

/s/ J. Jeffrey Peoples

J. Jeffrey Peoples

Chairman, President, and Chief Executive Officer

/s/ Moses H. Feagin

Moses H. Feagin

Executive Vice President, Chief Financial Officer, and Treasurer

February 14, 2024

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MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Georgia Power Company

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, 2023.

/s/ Kimberly S. Greene

Kimberly S. Greene

Chairman, President, and Chief Executive Officer

/s/ Aaron P. Abramovitz

Aaron P. Abramovitz

Executive Vice President, Chief Financial Officer, and Treasurer

February 14, 2024

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MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Mississippi Power Company

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, 2023.

/s/ Anthony L. Wilson

Anthony L. Wilson

Chairman, President, and Chief Executive Officer

/s/ Matthew P. Grice

Matthew P. Grice

Vice President, Chief Financial Officer, and Treasurer

February 14, 2024

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MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Southern Power Company and Subsidiary Companies

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, 2023.

/s/ Christopher Cummiskey

Christopher Cummiskey

Chairman and Chief Executive Officer

/s/ Gary Kerr

Gary Kerr

Senior Vice President, Chief Financial Officer, and Treasurer

February 14, 2024

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MANAGEMENT'S REPORT ON INTERNAL CONTROL OVER FINANCIAL REPORTING

Southern Company Gas and Subsidiary Companies

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, 2023.

/s/ James Y. Kerr II

James Y. Kerr II

Chairman, President, and Chief Executive Officer

/s/ Grace A. Kolvereid

Grace A. Kolvereid

Executive Vice President, Chief Financial Officer, and Treasurer

February 14, 2024

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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 2024 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, 11, 12, and 13 for each of the Subsidiary Registrants are omitted pursuant to General Instruction I(2)(c) of Form 10-K. Item 14 for each of the Subsidiary Registrants 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.

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The following represents fees billed to the Subsidiary Registrants in 2023 and 2022 by Deloitte & Touche LLP, each company's principal public accountant: