Research and Development	9 Months Ended
Jun. 30, 2025
Research and Development [Abstract]
Collaborative Arrangement Disclosure	20. Collaborative Arrangement In 2023, TVA, Ontario Power Generation, BWRX TCA sp. z.o.o., and GE Hitachi Nuclear Energy ("GEH") entered into a multi-party collaborative arrangement to advance the global deployment of the GEH BWRX-300 small modular reactor. GEH is responsible for standard design development. Under the agreement, TVA will contribute up to $93 million for design costs incurred by GEH through 2026. At the time feasibility is determined, TVA will have the right to use the design and may receive additional economic benefits. Payments pursuant to the agreement are recorded as research and development expense, which is reflected as Operating and maintenance expense on TVA's Consolidated Statement of Operations in the period incurred. TVA recorded no expenses related to this agreement for the three months ended June 30, 2025 and $12 million of expenses for the three months ended June 30, 2024. TVA recorded $10 million and $29 million of expenses related to this agreement for the nine months ended June 30, 2025 and 2024, respectively. TVA also had a $6 million letter of credit posted under this arrangement at June 30, 2025.

Research and Development

9 Months Ended

Jun. 30, 2025

20. Collaborative Arrangement

In 2023, TVA, Ontario Power Generation, BWRX TCA sp. z.o.o., and GE Hitachi Nuclear Energy ("GEH") entered into a multi-party collaborative arrangement to advance the global deployment of the GEH BWRX-300 small modular reactor. GEH is responsible for standard design development. Under the agreement, TVA will contribute up to $93 million for design costs incurred by GEH through 2026. At the time feasibility is determined, TVA will have the right to use the design and may receive additional economic benefits.

Payments pursuant to the agreement are recorded as research and development expense, which is reflected as Operating and maintenance expense on TVA's Consolidated Statement of Operations in the period incurred. TVA recorded no expenses related to this agreement for the three months ended June 30, 2025 and $12 million of expenses for the three months ended June 30, 2024. TVA recorded $10 million and $29 million of expenses related to this agreement for the nine months ended June 30, 2025 and 2024, respectively. TVA also had a $6 million letter of credit posted under this arrangement at June 30, 2025.