Tennessee Valley Authority

TVA's consolidated financial statements are prepared in accordance with accounting principles generally accepted in the U.S. ("GAAP"), which require management to make estimates, judgments, and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Each of these estimates varies in regard to the level of judgment involved and its potential impact on TVA's financial results. Estimates are deemed critical either when a different estimate could have reasonably been used, or where changes in the estimate are reasonably likely to occur from period to period, and such use or change also would materially impact TVA's financial condition, results of operations, or cash flows. TVA's critical accounting policies are discussed in Note 1— Summary of Significant Accounting Policies of the Notes to Consolidated Financial Statements.

TVA believes that its most critical accounting estimates relate to AROs, fair value measurements, and pension and other post-retirement benefits.

Management has discussed the development, selection, and disclosure of critical accounting estimates with the Audit, Risk, and Cybersecurity Committee of the TVA Board. While TVA's estimates and assumptions are based on its knowledge of current events and actions it may undertake in the future, actual results may ultimately differ from these estimates and assumptions.

Asset Retirement Obligations

TVA recognizes legal obligations associated with the future retirement of certain tangible long-lived assets. These obligations relate to TVA's generating facilities, including coal-fired, nuclear, hydroelectric, and natural gas and/or oil-fired. They also pertain to coal ash impoundments, transmission facilities, and other property-related assets. Activities involved with the retirement of these assets could include decontamination and demolition of structures, removal and disposal of wastes, and site restoration. TVA periodically reviews its estimated asset retirement obligation ("ARO") liabilities. Revisions to the ARO estimates are made whenever factors indicate that the timing or amounts of estimated cash flows have changed. Any change to an ARO liability is recognized prospectively as an equivalent increase or decrease in the carrying value of the capitalized asset. Any accretion or depreciation expense related to these liabilities and assets is charged to a regulatory asset. See Note 11 —Regulatory Assets and Liabilities — Nuclear Decommissioning Costsand Non-Nuclear Decommissioning Costs and Note 14 —Asset Retirement Obligationsfor explanations of changes in estimates.

The initial obligation is measured at its estimated fair value using various judgments and assumptions. Fair value is developed using an expected present value technique that is based on assumptions of market participants and that considers estimated retirement costs in current period dollars that are inflated to the anticipated decommissioning date and then discounted back to the date the ARO was incurred. Changes in assumptions and estimates included within the calculations of the value of the AROs could result in different results than those identified and recorded in the financial statements, including amortization of the regulatory assets.

Nuclear Decommissioning. Decommissioning cost studies are updated for each of TVA's nuclear unit's long-lived assets at least every five years. At September 30, 2025, the estimated future nuclear decommissioning cost recognized in the financial statements was $4.0 billion and was included in AROs, and the unamortized regulatory asset related to nuclear decommissioning ARO costs of $149 million was included in Regulatory assets.

The following key assumptions can have a significant effect on estimates related to the nuclear decommissioning costs reported in TVA's nuclear ARO liability:

Timing and Method – In projecting decommissioning costs, two assumptions must be made to estimate the timing of plant decommissioning. First, the date of the plant's retirement must be estimated. At Browns Ferry and Sequoyah, the estimated retirement date is based on the unit with the longest license period remaining. At Watts Bar, the estimated retirement date is based on each unit's license period. Second, an assumption must be made on the timing of the decommissioning. TVA has ascribed probabilities to two different decommissioning methods related to its nuclear decommissioning obligation estimate: the DECON method and the SAFSTOR method. The DECON method requires that radioactive contamination be removed from a site and safely disposed of or decontaminated to a level that permits the site to be released for unrestricted use shortly after it ceases operation. The SAFSTOR method allows nuclear facilities to be placed and maintained in a condition that allows the

facilities to be safely stored and subsequently decontaminated to levels that permit release for unrestricted use. TVA bases its nuclear decommissioning estimates on site-specific cost studies, which are updated for each of TVA's nuclear units at least every five years. Changes in probabilities ascribed to the assumptions or the timing of decommissioning can significantly change the present value of TVA's obligations.

Cost Estimates – There is limited experience with actual decommissioning of large nuclear facilities. Changes in technology and experience as well as changes in regulations regarding nuclear decommissioning could cause cost estimates to change significantly. TVA's cost studies assume current technology and regulations.

Cost Escalation Rate – TVA uses expected inflation rates over the remaining timeframe until the costs are expected to be incurred to estimate the amount of future cash flows required to satisfy TVA's decommissioning obligations.

Discount Rate – TVA uses its incremental borrowing rate over a period consistent with the remaining timeframe until the costs are expected to be incurred to calculate the present value of the weighted estimated cash flows required to satisfy TVA's decommissioning obligations.

The actual decommissioning costs may vary from the derived estimates because of changes in current assumptions, such as the assumed dates of decommissioning, changes in regulatory requirements, changes in technology, and changes in the cost of labor, materials, and equipment. A 10 percent change in TVA's forecasted costs for nuclear decommissioning activities at September 30, 2025, would have affected the liability by approximately $398 million.

Non-Nuclear Decommissioning. At September 30, 2025, the estimated future non-nuclear decommissioning cost recognized in the financial statements was $6.4 billion and was included in AROs, and the unamortized regulatory asset related to non-nuclear decommissioning ARO costs of $5.6 billion was included in Regulatory assets.

This decommissioning cost estimate involves estimating the amount and timing of future expenditures and making judgments concerning whether or not such costs are considered a legal obligation. Estimating the amount and timing of future expenditures includes, among other things, making projections of the timing and duration of the asset retirement process and predicting how costs will escalate with inflation. These costs are predominantly CCR closure, CCR post-closure care and monitoring, and plant powerhouse asbestos removal. CCR closure estimates are primarily closure-in-place except for specific ponds located at Allen and Gallatin, which are closure-by-removal. CCR post-closure care and monitoring primarily includes costs for grounds maintenance, cover system and mechanical maintenance, inspections, and groundwater monitoring costs. Asbestos removal is based on cost per square foot to remove and dispose of asbestos-containing materials. TVA revises estimates of CCR closure on a project by project basis when updated cost information becomes available that causes management's expectation of cost to change materially.

The following key assumptions can have a significant effect on estimates related to the non-nuclear decommissioning costs:

Timing and Method – In projecting non-nuclear decommissioning costs, the date of the asset's retirement must be estimated. In instances where the retirement of a specific asset will precede the retirement of the generating plant, the anticipated retirement date of the specific asset is used. Additionally, TVA expects to incur certain ongoing costs subsequent to the initial asset retirement. TVA develops its cost estimates based on likelihood of decommissioning method where options exist in fulfilling legal obligations (e.g., closure-in-place or closure-by-removal for coal ash impoundments). The decommissioning method is determined based on several factors including available technologies, environmental studies, cost factors, resource availability, and timing requirements. As these factors are considered and decommissioning closure methods are determined, the detailed project schedules and estimates are adjusted. Non-nuclear decommissioning cost estimates, including CCR post-closure care and monitoring costs and asbestos removal, are studied for revision at least every five years, but revised more frequently if updated cost information becomes available that causes management's expectation of cost to change materially. TVA completed the study of its non-nuclear plant decommissioning obligations in September 2025, resulting in a decrease of $27 million. See Note 11 — Regulatory Assets and Liabilities — Non-Nuclear Decommissioning Costs.

Technology and Regulation – Changes in technology and experience as well as changes in regulations regarding non-nuclear decommissioning could cause cost estimates to change significantly. TVA's cost estimates generally assume current technology and regulations. In April 2015, EPA published its final rule governing CCR, which regulates landfill and impoundment location, design, and operations; dictates certain pond-closure conditions; and establishes groundwater monitoring and closure and post-closure standards. On May 8, 2024, EPA published its Legacy CCR Rule, which expands the scope of the existing regulatory requirements of the 2015 CCR Rule to include two additional classes of units: Legacy SIs and CCRMUs. As a result of the enactment of the final rule, during 2024, TVA recorded additional estimated AROs of $3.1 billion and recorded a corresponding regulatory asset of $3.1 billion due to these AROs being associated with closed sites and asset retirement costs having been fully depreciated. In 2025, TVA recorded a net decrease of $500 million in the AROs related to the final Legacy CCR Rule for updated cost estimates. TVA continues to evaluate the impact of the rule on its operations, including cost and timing estimates of related projects. As a result, further adjustments to its ARO liabilities may be required as estimates are refined.

Cost Escalation Rate – TVA uses expected inflation rates over the remaining timeframe until the costs are expected to be incurred to estimate the amount of future cash flows required to satisfy TVA's decommissioning obligations.

Discount Rate – TVA uses its incremental borrowing rate over a period consistent with the remaining timeframe until the costs are expected to be incurred to calculate the present value of the weighted estimated cash flows required to satisfy TVA's decommissioning obligations.

The actual decommissioning costs may vary from the derived estimates because of changes in current assumptions, such as the assumed dates of decommissioning, changes in the discount or escalation rates, changes in regulatory requirements, changes in technology, and changes in the cost of labor, materials, and equipment. A 10 percent change in TVA's forecasted costs for non-nuclear decommissioning activities at September 30, 2025, would have affected the liability by approximately $644 million.

Investments. Investment funds are comprised of equity securities and debt securities and are classified as trading. These securities are held in the Nuclear Decommissioning Trust ("NDT"), Asset Retirement Trust ("ART"), Supplemental Executive Retirement Plan ("SERP"), Deferred Compensation Plan ("DCP"), Restoration Plan ("RP"), and qualified benefit pension plan.

Investment Funds. The assets in the NDT, ART, SERP, DCP, and RP are generally measured at fair value based on quoted market prices or other observable market data such as interest rate indices. These investments are primarily U.S. and international equities, real estate investment trusts, fixed income investments, high-yield fixed income investments, U.S. Treasury Inflation-Protected Securities ("TIPS"), treasuries, currencies, derivative instruments, and other investments. TVA has classified all of these trading securities as either Level 1, Level 2, or Investments measured at net asset value ("NAV"). Private equity limited partnerships, private real asset investments, and private credit investments may include holdings of investments in private real estate, venture capital, buyout, mezzanine or subordinated debt, restructuring or distressed debt, and special situations through funds managed by third-party investment managers. These investments are valued at NAV as a practical expedient for fair value. There are no readily available quoted exchange prices for these investments. The fair value of these investments is based on information provided by the investment managers. These investments are valued on a quarterly basis. See Note 17 — Fair Value Measurements — Valuation Techniques for a discussion of valuation levels of the investments.

Plan Investments. TVA's qualified benefit pension plan is funded with qualified plan assets. These investments are primarily global public equities, private equities, fixed income securities, public real assets, and private real assets. See Note 21 —Benefit Plans — Fair Value Measurements for disclosure of fair value measurements for investments held by the TVA Retirement System ("TVARS") that support TVA's qualified defined benefit pension plan.

Pricing. Prices provided by third parties for the assets in investment funds and plan investments are subjected to automated tolerance checks by the investment portfolio trustee to identify and avoid, where possible, the use of inaccurate prices. Any such prices identified as outside the tolerance thresholds are reported to the vendor that provided the price. If the prices are validated, the primary pricing source is used. If not, a secondary source price that has passed the applicable tolerance check is used (or queried with the vendor if it is out of tolerance), resulting in either the use of a secondary price, where validated, or the last reported default price, as in the case of a missing price. For monthly valued accounts, where secondary price sources are available, an automated inter-source tolerance report identifies prices with an inter-vendor pricing variance of over two percent at an asset class level. For daily valued accounts, each security is assigned, where possible, an indicative major market index, against which daily price movements are automatically compared. Tolerance thresholds are established by asset class. Prices found to be outside of the applicable tolerance threshold are reported and queried with vendors as described above.

For investment funds, TVA additionally performs its own analytical testing on the change in fair value measurements each period to ensure the valuations are reasonable based on changes in general market assumptions. TVA also performs pricing tests on various portfolios comprised of securities classified in Levels 1 and 2 on a quarterly basis to confirm accuracy of the values received from the investment portfolio trustee. For plan investments, TVARS reviews the trustee's Service Organization Controls report and the pricing policies of the trustee's largest pricing vendor.

Derivatives. TVA has historically entered into various derivative transactions, including commodity option contracts, forward contracts, swaps, swaptions, futures, and options on futures, to manage various market risks. Other than certain derivative instruments included in investment funds, it is TVA's policy to enter into these derivative transactions solely for hedging purposes and not for speculative purposes. See Note 11 —Regulatory Assets and Liabilitiesand Note 16 —Risk Management Activities and Derivative Transactionsfor explanations of changes in estimates.

Currency and Interest Rate Derivatives. TVA has two currency swaps and two "fixed for floating" interest rate swaps. The currency swaps protect against changes in cash flows caused by volatility in exchange rates related to outstanding Bonds denominated in British pounds sterling. TVA uses interest rate swaps to fix variable short-term debt to a fixed rate. The currency and interest rate swaps are classified as Level 2 valuations as the rate curves and interest rates affecting the fair value of the contracts are based on observable data.

Commodity Contract Derivatives. TVA enters into certain commodity contract derivatives for natural gas that require physical delivery of the contracted quantity. The natural gas commodity contract derivatives are classified as Level 2 valuations based on market approaches which utilize short-term and mid-term market-quoted prices from an external industry brokerage firm.

TVA maintains policies and procedures to value commodity contracts using what is believed to be the best and most relevant data available. In addition, TVA's risk management group reviews valuations and pricing data.

Commodity Derivatives under the Financial Hedging Program ("FHP"). Currently, TVA is hedging exposure to the price of natural gas under the FHP. There is no Value at Risk aggregate transaction limit under the current FHP structure, but the TVA Board reviews and authorizes the use of tolerances and measures. The commodity derivatives under the FHP are classified as Level 2 valuations based on market approaches which utilize short-term and mid-term market-quoted prices from an external industry brokerage firm.

Fair Value Considerations. In determining the fair value of its financial instruments, TVA considers the source of observable market data inputs, liquidity of the instrument, credit risk, and risk of nonperformance of itself or the counterparty to the contract. The conditions and criteria used to assess these factors are described below.

Sources of Market Assumptions. TVA derives its financial instrument market assumptions from market data sources (e.g., Chicago Mercantile Exchange and Moody's Investors Service, Inc. ("Moody's")). In some cases, where market data is not readily available, TVA uses comparable market sources and empirical evidence to derive market assumptions and determine a financial instrument's fair value.

Market Liquidity. Market liquidity is assessed by TVA based on criteria as to whether the financial instrument trades in an active or inactive market. A financial instrument is considered to be in an active market if the prices are fully transparent to the market participants, the prices can be measured by market bid and ask quotes, the market has a relatively high trading volume, and the market has a significant number of market participants that will allow the market to rapidly absorb the quantity of the assets traded without significantly affecting the market price. Other factors TVA considers when determining whether a market is active or inactive include the presence of government or regulatory control over pricing that could make it difficult to establish a market-based price upon entering into a transaction.

Nonperformance Risk. In determining the potential impact of nonperformance risk, which includes credit risk, TVA considers changes in current market conditions, readily available information on nonperformance risk, letters of credit, collateral, other arrangements available, and the nature of master netting arrangements. TVA is a counterparty to derivative instruments that subject TVA to nonperformance risk. Nonperformance risk on the majority of investments and certain exchange-traded instruments held by TVA is incorporated into the exit price that is derived from quoted market data that is used to value the investment.

Nonperformance risk for most of TVA's derivative instruments is an adjustment to the initial asset/liability fair value. TVA adjusts for nonperformance risk, both of TVA (for liabilities) and the counterparty (for assets), by applying a credit valuation

adjustment ("CVA"). TVA determines an appropriate CVA for each applicable financial instrument based on the term of the instrument and TVA's or the counterparty's credit rating as obtained from Moody's. For companies that do not have an observable credit rating, TVA uses internal analysis to assign a comparable rating to the company. TVA discounts each financial instrument using the historical default rate (as reported by Moody's for CY 1983 to CY 2024) for companies with a similar credit rating over a time period consistent with the remaining term of the contract.

All derivative instruments are analyzed individually and are subject to unique risk exposures. The application of CVAs resulted in a less than $1 million decrease in the fair value of assets and a $3 million decrease in the fair value of liabilities at September 30, 2025.

Collateral. TVA's interest rate swaps, currency swaps, and commodity derivatives under the FHP contain contract provisions that require a party to post collateral (in a form such as cash or a letter of credit) when the party's liability balance under the agreement exceeds a certain threshold. See Note 16 —Risk Management Activities and Derivative Transactions — Other Derivative Instruments —Collateral for a discussion of collateral related to TVA's derivative liabilities.

Pension and Other Post-Retirement Benefits

TVA sponsors a defined benefit pension plan that is qualified under section 401(a) of the Internal Revenue Code and covers substantially all of its full-time annual employees hired prior to July 1, 2014. TVARS, a separate legal entity governed by its own board of directors (the "TVARS Board"), administers the qualified defined benefit pension plan. TVA also provides a SERP to certain executives in critical positions, which provides supplemental pension benefits tied to compensation levels that exceed limits imposed by IRS rules applicable to the qualified defined benefit pension plan. Additionally, TVA provides post-retirement health care benefits for most of its full-time employees who reach retirement age while still working for TVA.

TVA's pension and other post-retirement benefits contain uncertainties because they require management to make certain assumptions related to TVA's cost to provide these benefits. Numerous factors are considered including the provisions of the plans, changing employee demographics, various actuarial calculations, assumptions, and accounting mechanisms.

Certain key actuarial assumptions critical to the pension and postretirement accounting estimates include expected long-term rate of return on plan assets, discount rates, projected health care cost trend rates, cost of living adjustments ("COLA"), and mortality rates. Every five years, a formal actuarial experience study that compares assumptions to the actual experience is conducted. Additional ad-hoc experience studies are performed as needed to review recent experience and validate recommended changes to the actuarial assumptions used based upon TVA's last experience study in 2023. See Note 21 —Benefit Plans for explanations of changes in assumptions and estimates.

Expected Return on Plan Assets. The qualified defined benefit pension plan is the only plan that is funded with qualified plan assets. In determining the expected long-term rate of return on pension plan assets, TVA uses a process that incorporates actual historical asset class returns and an assessment of expected future performance and takes into consideration external actuarial advice, the current outlook on capital markets, the asset allocation policy, and the anticipated impact of active management. In June 2025, the TVARS Board approved a new asset allocation policy, but had no changes to the 6.50 percent expected return on assets assumption adopted in 2022.

TVA recognizes the impact of asset performance on pension expense over a three-year phase-in period through a market-related value of assets ("MRVA") calculation. The MRVA recognizes investment gains and losses over a three-year period and is used in calculating the expected return on assets and the recognized net actuarial loss components of pension net periodic benefit cost.

A higher expected rate of return assumption decreases the net periodic pension benefit costs, whereas a lower expected rate of return assumption increases the net periodic pension benefit cost. The plan's actual rate of return for 2025 was 4.90 percent compared to the assumption of 6.50 percent. The difference between the expected and actual return on plan assets resulted in an actuarial loss of $93 million that is recognized as an increase in the related regulatory asset and an increase in the pension benefit obligation at September 30, 2025.

Discount Rate. TVA's discount rates are derived by identifying a theoretical settlement portfolio of high quality corporate bonds of Aa quality or higher sufficient to provide for the projected benefit payments. The model matches the present value of the projected benefit payments to the market value of the theoretical settlement bond portfolio with any resulting excess funds presumed to be reinvested and used to meet successive year benefit payments. A single equivalent discount rate is determined to align the present value of the required cash flow with the value of the bond portfolio. The resulting discount rates are reflective of both the current interest rate and the distinct liability of the pension and post-retirement benefit plans.

The discount rate is somewhat volatile because it is determined based upon the prevailing rate of long-term corporate bonds as of the measurement date. A higher discount rate decreases the plan obligations and correspondingly decreases the net periodic pension and net post-retirement benefit costs for those plans where actuarial losses are being amortized. Alternatively, a lower discount rate increases net periodic pension and net periodic post-retirement benefit costs. The discount rates used to determine the pension and post-retirement benefit obligations were 5.47 percent and 5.62 percent, respectively, at September 30, 2025.

Health Care Cost Trends. In establishing health care cost trend rates for the post-retirement obligation, TVA reviews actual recent cost trends and projected future trends considering health care inflation, changes in health care utilization, and changes in plan benefits and premium experience. The pre-Medicare eligible per capita claims costs and per capita contributions trend rates are both reset to the initial rate of 7.75 percent, declining 0.50 percent in 2026 and 0.25 percent per year thereafter until they reach the ultimate trend rate of 5.00 percent in 2036. The post-Medicare current health care cost trend rate is zero percent for years 2025 through 2028, reaching the ultimate rate of 4.00 percent in 2029. TVA recognized a $28 million gain from the change in post-Medicare health care cost trend rate due to the Medicare supplement insurance premiums on the private exchange escalating at a lower rate than previously assumed. Additionally, TVA recognized an $18 million actuarial gain to reflect changes in the observed and anticipated pre-Medicare per capita claims costs and contributions. The net actuarial gains from health cost trends and observed and anticipated plan experience are recognized as an increase in the related regulatory liability and a decrease in the post-retirement obligation at September 30, 2025.

Cost of Living Adjustments. COLAs are an increase in the benefits for eligible retirees to help maintain the purchasing power of benefits as consumer prices increase. This assumption is based on the long-term expected future rate of inflation, which is based on the capital market outlooks, economic forecasts, and the Federal Reserve policy. See Note 21— Benefit Plans — Plan Assumptions — Cost of Living Adjustment for further discussion on the calculation of the COLA. The actual COLA for CY 2025 was 2.77 percent. The CY 2026 COLA is assumed to be 2.49 percent, and for years thereafter the COLA is assumed to be 2.00 percent. A higher COLA increases the pension benefit obligation whereas a lower COLA assumption decreases the obligation. The actual CY COLA and the long-term COLA assumption are used to determine the benefit obligation at September 30 and the net periodic benefit costs for the following fiscal year.

Mortality. TVA's mortality assumptions are based upon actuarial projections in combination with actuarial studies of the actual mortality experience of TVARS's pension and post-retirement benefit plan participants taking into consideration the Society of Actuaries ("SOA") mortality table and projection scales as of September 30, 2025. TVA continues to monitor the availability of updates to mortality tables, longevity improvement scales, and mortality reviews and experience studies to consider whether these updates should be reflected in the current year mortality assumption.

The following tables illustrate the estimated effects of changing certain of the critical actuarial assumptions discussed above, while holding all other assumptions constant and excluding any impact for unamortized actuarial gains and losses: