Vistra: 2025 Third-Party Emissions Assurance

STATEMENT OF GREENHOUSE GAS ("GHG") EMISSIONS FOR THE YEAR ENDED DECEMBER 31, 2025

The management of Vistra Corp. ("Vistra" or the "Company") is responsible for the completeness, accuracy, and validity of the Company's Statement of GHG Emissions (the "2025 Statement of GHG Emissions").

Management is also responsible for the collection, quantification, and presentation of the 2025 Statement of GHG Emissions and for the selection of the criteria, which management believes to provide an objective basis for measuring and reporting. Management of Vistra asserts that the 2025 Statement of GHG Emissions for the year ended December 31, 2025, is presented in accordance with the Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (Revised Edition), published by the World Resources Institute/World Business Council for Sustainable Development (the "GHG Protocol").

Vistra (NYSE: VST) is a leading Fortune 500 integrated retail electricity and power generation company based in Irving, Texas, that provides essential power resources to customers, businesses, and communities from California to Maine.

‌Vistra is one of the largest competitive power generator in the U.S., with a capacity of approximately 44,000 megawatts, operating in all of the major competitive wholesale markets in the country. Vistra is a leader in energy transformation and expansion with an unyielding focus on reliability, affordability, and sustainability, powered by a diverse portfolio that includes natural gas, nuclear, coal, solar, and battery energy storage facilities. The Company continues to grow its zero-carbon resources, operating the second-largest fleet of competitive nuclear power plants in the country, substantial battery energy storage capacity, and a growing number of solar facilities.

‌Vistra is one of the largest competitive electricity providers in the country and takes an innovative, customer-centric approach to retail, offering solutions to meet customers' needs, including more than 50 renewable energy plans. Through its family of retail brands, Vistra serves approximately 5 million residential, commercial, and industrial retail customers.

‌As a leader in the responsible transformation of the country's energy supply, Vistra has made significant progress towards its 2030 and 2050 targets. The Company has committed to a 60% reduction of Scope 1 and 2 greenhouse gas emissions by 2030, as compared to our 2010 baseline, and net-zero carbon emissions by 2050, assuming necessary technological advancements and public policy incentives are achieved. Learn more about our environmental, social, and governance efforts and read the Company's sustainability report at https://vistracorp.com/sustainability/.‌

The 2025 Statement of GHG Emissions has been prepared based on a calendar reporting year that is the same as the Company's financial reporting period of January 1, 2025, to December 31, 2025. The disclosures included in the 2025 Statement of GHG Emissions for the calendar year ended December 31, 2025, are presented in accordance with the GHG Protocol.

A summary of the key disclosure policies is set out below.

1 Base year for Scope 1 GHG emissions is 2010, base year for Scope 2 location-based GHG emissions is 2018, and base year for Scope 2 market-based GHG emissions is 2023.

2 This information was not subject to review by Deloitte & Touche LLP and, accordingly, Deloitte & Touche does not express a conclusion or any form of assurance on such information.

3 Total GHG Emissions represent total Scope 1 and total Scope 2 location-based GHG Emissions.

The 2025 Statement of GHG Emissions includes Scope 1 and Scope 2 GHG emissions reported for operations with the organizational boundary described below.

Specifically:

• Scope 1 GHG emissions include all relevant GHG emissions emitted directly from the Company's activities, including fuel combustion in boilers, turbines, and engines used for wholesale electric power production. Scope 1 GHG emissions are reported as required under the U.S. EPA's Mandatory Reporting Rule (40 CFR 98) and include ancillary boilers and heaters used at the facilities for operations but does not include mobile equipment nor fugitive emissions, as they are not a material source of emissions.

• Scope 2 GHG emissions include indirect GHG emissions from consumption of purchased electricity by the Company. Scope 2 GHG emissions are calculated using both location-based and market-based methodologies.

GHG emissions have been reported according to the equity share approach as defined by the GHG Protocol. GHG emissions that pertain to the organizational and operational boundaries have been reported for the Company owned buildings and power generation facilities, including facilities that are not required to report direct emissions under the US EPA's Mandatory Reporting Rule, and the Company's real estate financial and operating leases located in the United States. The Company's policy is to report Scope 1 and Scope 2 emissions data from a facility in the year in which the facility is acquired, unless the emissions data is not readily available as of the date of the report.

The base year for Scope 1 GHG emissions is 2010. The Scope 2 location-based GHG emissions base year is 2018, the first year Vistra calculated Scope 2 location-based GHG emissions. The Scope 2 market-based GHG emissions base year is 2023, the first year Vistra calculated Scope 2 market-based GHG emissions. Vistra's emissions reduction target of 60% by 2030 includes Scope 2 location-based GHG emissions, even though these emissions for the base year 2010 are not available. Vistra's Scope 2 location-based GHG emissions are not a material driver of its overall emissions profile, consistently representing less than 0.5% of the total GHG emissions. As such, Vistra's Scope 2 location-based GHG emissions represent an immaterial addition to the target base year's emissions.

Vistra has established a recalculation policy to update base year calculations when cumulative changes to methodology would result in changes exceeding a 5% threshold. While the GHG Protocol makes no specific recommendations as to what constitutes a significant threshold for baseline recalculation, 5% is comparable with the GHG protocol on materiality where "an error is considered to be materially misleading if its value exceeds 5% of the total inventory for the part of the organization being verified." This threshold applies to structural changes in the reporting organization, changes in emission calculation methodology, improvements in the accuracy of the emission conversion factors, or improvements in the accuracy of the emissions activity data.

GHG emissions are reported in metric tons of carbon dioxide equivalents (CO2e) and include three of the seven greenhouse gases covered by the Kyoto Protocol-carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), Sulphur hexafluoride (SF6), and nitrogen trifluoride (NF3) emissions have been omitted from our reporting as they are not a material source of greenhouse gases for the Company. The table below includes total Scope 1 and Scope 2 location-based GHG emissions by gas in metric tons and metric tons of CO2e.

For Scope 1 GHG emissions, fuel usage, directly monitored emissions and heat input are used to calculate GHG emissions. The primary data is collected in each facility's central Data Acquisition Handling System. The corporate environmental team then calculates the associated GHG emissions through the application of appropriate GHG calculations using emission factors, as described in "GHG emissions factors" below.

For Scope 2 location-based GHG emissions, metered electricity purchases from electricity distribution utilities were collected for each facility by the corporate accounting team. The corporate sustainability team calculates the associated GHG emissions via IBM Envizi, which uses the emission factors as described in the "GHG emissions factors" below.

For Scope 2 market-based GHG emissions, energy attribute certificates (EACs) including Renewable Energy Certificates (RECs) and Emission Free Energy Certificates (EFECs) were utilized and retired per GHG Protocol. The corporate sustainability team calculates the associated GHG emissions via IBM Envizi, which uses the emission factors as described in the "GHG emissions factors" below.

Measurement of Scope 1 and Scope 2 GHG emissions includes estimates and assumptions that are subject to inherent measurement uncertainty resulting, for example, from accuracy and precision of GHG emission factors. The selection of different but acceptable measurement methods, input data, or assumptions may have resulted in different amounts or disclosures being reported.

The CO2e emissions associated with the activities noted above have been determined by directly measured GHG emissions multiplied by appropriate conversion factors or on the basis of measured or estimated energy and fuel use, multiplied by relevant GHG emission factors.

The table below indicates the relevant emission factors applied to current inventories.

Management of Vistra Corp.:

We have reviewed management of Vistra Corp.'s ("Vistra" or the "Company") assertion that the accompanying Statement of Greenhouse Gas ("GHG") Emissions for the year ended December 31, 2025 (the "2025 Statement of GHG Emissions") is presented in accordance with the Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (Revised Edition), published by the World Resources Institute/World Business Council for Sustainable Development (the "GHG Protocol", or "Criteria") ("management's assertion"). The Company's management is responsible for its assertion. Our responsibility is to express a conclusion on management's assertion based on our review.

Our review was conducted in accordance with attestation standards established by the American Institute of Certified Public Accountants. Those standards require that we plan and perform the review to obtain limited assurance about whether any material modifications should be made to management's assertion in order for it to be presented in accordance with the Criteria. The procedures performed in a review vary in nature and timing from, and are substantially less in extent than, an examination, the objective of which is to obtain reasonable assurance about whether management's assertion is presented in accordance with the Criteria, in all material respects, in order to express an opinion. Accordingly, we do not express such an opinion.

Because of the limited nature of the engagement, the level of assurance obtained in a review is substantially lower than the assurance that would have been obtained had an examination been performed. We believe that the review evidence obtained is sufficient and appropriate to provide a reasonable basis for our conclusion.

We are required to be independent and to meet our other ethical responsibilities in accordance with relevant ethical requirements related to the engagement.

The procedures we performed were based on our professional judgment. In performing our review, we performed analytical procedures, inquiries, and other procedures as we considered necessary in the circumstances. For a selection of the specified information, we performed tests of mathematical accuracy of computations or compared specified information to underlying records.

The preparation of the 2025 Statement of GHG Emissions requires management to interpret the Criteria, make determinations as to the relevancy of information to be included, and make estimates and assumptions that affect the reported information. Measurement of Scope 1 and Scope 2 GHG emissions may include estimates and assumptions that are subject to substantial inherent measurement uncertainty, including for example, the accuracy and precision of conversion factors or other estimation methodologies used by management. Obtaining sufficient, appropriate review evidence to support our conclusion does not reduce the inherent uncertainty in the amounts and disclosures. The selection by management of different but acceptable measurement methods, input data, or assumptions, may have resulted in materially different amounts or disclosures being reported.

Our review was limited to the disclosures within the 2025 Statement of GHG Emissions. Any information relating to periods prior to December 31, 2019 for Scope 1 GHG emissions or prior to December 31, 2020 for Scope 2 GHG emissions, was not subject to our review and, accordingly, we do not express a conclusion or any form of assurance on such information. Further, any information relating to forward-looking statements, targets, goals, progress against goals, and linked information was not subject to our review and, accordingly, we do not express a conclusion or any form of assurance on such information.

Based on our review, we are not aware of any material modifications that should be made to management's assertion in order for it to be presented in accordance with the GHG Protocol.

April 28, 2026

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