Isle of Man, UK--(Marketwire - May 31, 2007) - PRESS RELEASE

For immediate release

31 May 2007


                         CLIMATE EXCHANGE PLC


             NRG Energy, Inc. Joins Chicago Climate Exchange

The Chicago Climate Exchange, a wholly owned subsidiary of Climate Exchange Plc, announces that NRG Energy, Inc. has joined the exchange.

The full text of NRG Energy, Incorporated's press release follows:

            "NRG Energy, Inc. Joins Chicago Climate Exchange:

       Supports First Voluntary Greenhouse Gas Emissions Reduction,
                        Registry and Trading Program

Princeton, NJ; May 30, 2007 - NRG Energy, Inc. (NYSE: NRG) has joined the Chicago Climate Exchange (CCX), the world's first voluntary and legally binding greenhouse gas emissions reduction, registry and trading program. NRG joins global companies such as Bayer Corporation, Ford, IBM and Intel as a member.

"Joining the Chicago Climate Exchange is part of our ongoing program to increase our carbon awareness, track our emissions, and address climate change proactively," said David Crane, President and CEO, NRG Energy, Inc. "A cap-and-trade system, like CCX's, will minimize the cost of achieving carbon reductions because it allows the lowest cost emission reductions to be used to help meet reduction targets."

CCX is the world's first and North America's only legally binding rules-based greenhouse gas emissions allowance trading system, as well as the world's only global system for emissions trading based on all six greenhouse gases.

Dr. Richard Sandor, Chairman and Chief Executive Officer of CCX said, "In joining CCX, NRG continues its pioneering efforts to address climate change and help develop mitigation options, as well as contribute to the building of the CCX global emissions reduction and trading system. As a financial institution with economic, environmental and social objectives, CCX is proud of the contribution NRG will make and we look forward to their collaboration and participation."

About NRG

A Fortune 500 company, NRG Energy, Inc. owns and operates a diverse portfolio of power-generating facilities, primarily in Texas and the Northeast, South Central and Western regions of the United States. Its operations include baseload, intermediate, peaking, and cogeneration facilities and thermal energy production. NRG also has ownership interests in generating facilities in Australia, Germany and Brazil. More information on NRG is available at www.nrgenergy.com.

About CCX

CCX members are leaders in greenhouse gas management and represent all sectors of the global economy, as well as public sector innovators. Reductions achieved through CCX are the only reductions in North America being achieved through a legally binding compliance regime, with price transparency and independent third party verification provided by NASD. The Chairman and CEO of CCX is economist and financial innovator Dr. Richard L. Sandor, who was named a Hero of the Planet by Time magazine for his work in founding CCX. For a full list of CCX members, daily prices and other program information, see www.chicagoclimateexchange.com. CCX is a wholly owned subsidiary of Climate Exchange Plc, a public stock company listed on the AIM Market of the London Stock Exchange. Climate Exchange Plc also owns the European Climate Exchange, Europe's leading CO2 emissions exchange.

This news release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Such forward-looking statements are subject to certain risks, uncertainties and assumptions and typically can be identified by the use of words such as "will," "expect," "believe," and similar terms. Although NRG believes that its expectations are reasonable, it can give no assurance that these expectations will prove to have been correct, and actual results may vary materially.

NRG undertakes no obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise. The foregoing review of factors that could cause NRG's actual results to differ materially from those contemplated in the forward-looking statements included in this news release should be considered in connection with information regarding risks and uncertainties that may affect NRG's future results included in NRG's filings with the Securities and Exchange Commission at www.sec.gov."

Neil Eckert, CEO, Climate Exchange Plc             0207 382 7807
David Haggie/Peter Rigby, Haggie Financial         0207 417 8989







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       The company news service from the London Stock Exchange