Vistra Corp.

13. FAIR VALUE MEASUREMENTS

Fair value measurements are based upon inputs that market participants use in pricing an asset or liability, which are characterized according to a hierarchy that prioritizes those inputs based on the degree to which they are observable. Observable inputs represent market data obtained from independent sources, whereas unobservable inputs reflect our own market assumptions. We categorize our assets and liabilities recorded at fair value based upon the following fair value hierarchy as defined by GAAP:

•Level 1 valuations use quoted prices in active markets for identical assets or liabilities that are accessible at the measurement date.

•Level 2 valuations use over-the-counter broker quotes, quoted prices for similar assets or liabilities that are corroborated by correlations or other mathematical means, and other valuation inputs such as interest rates and yield curves observable at commonly quoted intervals.

•Level 3 valuations use unobservable inputs for the asset or liability, typically reflecting our estimate of assumptions that market participants would use in pricing the asset or liability. The fair value is therefore determined using model-based techniques, including discounted cash flow models.

The fair value input hierarchy level to which an asset or liability measurement in its entirety falls is determined based on the lowest level input that is significant to the measurement.

Assets and Liabilities Measured at Fair Value on a Recurring Basis

Assets and liabilities measured at fair value on a recurring basis consisted of commodity contracts, interest rate swaps accounted for as derivatives, and NDT investments. See Note 12 for additional information on our derivative positions.

NDT Investments — NDT investments include debt, equity, and other securities held for the purpose of funding the future retirement and decommissioning of our nuclear generation facilities consistent with investment rules established by the NRC and the PUCT. The NDT investments are included in Investments in the condensed consolidated balance sheets. There were no significant concentrations of credit risk from an individual counterparty or groups of counterparties in our NDT portfolio as of March 31, 2026.

Assets and liabilities measured at fair value on a recurring basis consisted of the following at the respective balance sheet dates shown below:

(a)Fair values are determined at the individual contract level. As certain contracts give rise to both asset and liability positions, reclassification adjustments are required to reconcile these amounts to the gross presentation in the condensed consolidated balance sheets.

(b)The investment objective for NDT equity securities is to invest tax efficiently and to match the performance of the S&P 500 and Russell 3000 Indices for U.S. equity investments and the MSCI EAFE and MSCI All Country World ex-US Indices for non-U.S. equity investments.

(c)The investment objective for NDT debt securities is to invest in a diversified, high quality, tax efficient portfolio. The debt securities are weighted with government and investment grade corporate bonds. Other investable debt securities include, but are not limited to, municipal bonds, high yield bonds, securitized bonds, non-U.S. developed bonds, emerging market bonds, loans and treasury inflation-protected securities. The debt securities had an average coupon rate of 3.97% and 4.02% as of March 31, 2026 and December 31, 2025, respectively, and an average maturity ofeight years as of each of March 31, 2026 and December 31, 2025, respectively. NDT debt securities held as of March 31, 2026 mature as follows: $937 million in one to five years, $1.221 billion in five to 10 years and $537 million after 10 years.

(d)Net asset value is a practical expedient used for the classification of assets that do not have readily determinable fair values and therefore are not classified in the fair value hierarchy.

The following tables present the fair value of Level 3 assets and liabilities by major contract type and the significant unobservable inputs used in the valuations as of March 31, 2026 and December 31, 2025:

(a)(i) Electricity purchase and sales contracts include power and Heat Rate positions in ERCOT, PJM, ISO-NE, NYISO, MISO, and CAISO regions, (ii) Options consist of physical electricity options, spread options, and natural gas options, (iii) Forward purchase contracts (swaps and options) used to hedge electricity price differences between settlement points are referred to as CRRs in ERCOT and FTRs in PJM, ISO-NE, NYISO, and MISO regions, and (iv) Natural gas contracts include swaps and forward contracts.

(b)The range of the inputs may be influenced by factors such as time of day, delivery period, season, and location. The average represents the arithmetic average of the underlying inputs and is not weighted by the related fair value or notional amount.

(c)Primarily based on the historical range of forward average hourly ERCOT North Hub and ERCOT South and West Zone prices.

(d)Primarily based on historical forward ERCOT and PJM power prices and ERCOT Heat Rate variability.

(e)Primarily based on the historical forward correlation and volatility within ERCOT and PJM.

(f)While we use the market approach, there is insufficient market data for the inputs to the valuation to consider the valuation liquid.

(g)Primarily based on the historical price differences between settlement points within ERCOT hubs and load zones.

(h)Primarily based on the historical forward PJM and Northeast natural gas basis prices and fixed prices.

(i)Primarily based on the historical forward natural gas fixed prices.

(j)Other includes contracts for coal and environmental allowances.

The following table presents the changes in fair value of Level 3 assets and liabilities:

(a)Settlements reflect reversals of unrealized mark-to-market valuations previously recognized in net income. Purchases and issuances reflect option premiums paid or received, including CRRs and FTRs.

(b)Transfers into Level 3 include instruments for which significant valuation inputs became unobservable due to changes in market conditions. For the three months ended March 31, 2026 and March 31, 2025, all transfers into Level 3 were from Level 2 and primarily consisted of power derivatives for which forward pricing inputs became unobservable.

(c)Transfers out of Level 3 include instruments for which previously unobservable valuation inputs became observable. All transfers out of Level 3 during the periods presented were to Level 2. For the three months ended March 31, 2026, transfers out of Level 3 primarily consisted of power derivatives for which forward pricing inputs became observable. For the three months ended March 31, 2025, transfers out of Level 3 primarily consisted of power and coal derivatives for which forward pricing inputs became observable.

Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis

Certain assets and liabilities are measured at fair value on a nonrecurring basis. These assets and liabilities are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances. These assets and liabilities can include inventories, assets acquired and liabilities assumed in business combinations, goodwill and other long-lived assets that are written down to fair value when they are determined to be impaired or held for sale.

The Lotus Acquisition was accounted for under the acquisition method which requires all assets acquired and liabilities assumed in the acquisition be recorded at fair value at the acquisition date. See Note 2 for additional information.

Fair Value of Debt

The fair value of our debt categorized as level 2 is based on observable market prices in less active markets. The fair value of our debt categorized as level 3 is based on security pricing from an independent party who uses broker quotes and third-party pricing services to determine fair values.