Regulatory Matters	9 Months Ended
Regulatory Matters	Sep. 30, 2025
Regulated Operations [Abstract]
Regulatory Matters	Regulatory Matters Environmental regulatory matters are discussed within Note 16, Environmental Matters. NRG operates in a highly regulated industry and is subject to regulation by various federal, state and provincial agencies. As such, NRG is affected by regulatory developments at the federal, state and provincial levels and in the regions in which NRG operates. In addition, NRG is subject to the market rules, procedures, and protocols of the various ISO and RTO markets in which NRG participates. These power markets are subject to ongoing legislative and regulatory changes that may impact NRG's wholesale and retail operations. In addition to the regulatory proceedings noted below, NRG and its subsidiaries are parties to other regulatory proceedings arising in the ordinary course of business or have other regulatory exposure. In management's opinion, the disposition of these ordinary course matters will not materially adversely affect NRG's consolidated financial position, results of operations, or cash flows. California Station Power — As the result of unfavorable final and non-appealable litigation, the Company accrued a liability associated with consumption of station power at the Company's Encina power plant facility in California after August 30, 2010. The Company believes it has established an appropriate accrual pending potential regulatory action by San Diego Gas & Electric regarding the Company's Encina facility. NYSPSC – Order to Show Cause — The NYSPSC issued an order referred to as the Retail Reset Order in December 2019 that limited the offers of ESCOs for electric and natural gas to three compliant products: guaranteed savings from the utility default rate, a fixed rate commodity product that is priced at no more than 5% greater than the trailing 12-month average utility supply rate or New York-sourced renewable energy that is at least 50% greater than the prevailing New York Renewable Energy Standard for load serving entities. The order effectively limited ESCOs’ offers to natural gas customers to only the guaranteed savings and capped fixed term compliant products because no equivalent renewable energy product exists for natural gas. Subsequently, the NYSPSC issued an order referred to as the Clarification Order on September 18, 2020 stating the Retail Reset Order applies only to prospective customer contracts. NRG took action to comply with the order when it became effective April 16, 2021. On January 8, 2024, the NYSPSC notified eight of NRG's retail energy suppliers (serving both electricity and natural gas) of alleged non-compliance with New York regulatory requirements. Among other items, the notices allege that the NRG suppliers did not transition existing residential customers to one of the three compliant products authorized by the NYSPSC following the effective date of the order. NRG responded to the notices in February 2024. On September 23, 2025, the NYSPSC issued a follow-up order repeating the above and related allegations, and also alleging separately that the NRG retail supplier responsible for selling natural gas to commercial and industrial customers had been improperly serving residential customers. The follow-up order directed NRG to show cause why consequences, ranging from sales monitoring, fines, refunds, debarment and/or eligibility revocation, should not be imposed for failure to comply with the Retail Reset Order and other Commission directives. The Company believes it has complied with the law and applicable orders and does not agree with the NYSPSC's assertions. The Company is in the initial stage of preparing a defense to this matter and has served discovery requests to support its position.