Exelon Corp. is the third utility to leave the U.S. Chamber of Commerce in the past week, following moves by California utility PG&E Corp. and New Mexico–based PNM Resources. Exelon, the largest nuclear operator in the U.S., cited the “organization’s opposition to climate legislation” for its decision, an allegation the business federation refuted on Tuesday.

“The carbon-based free lunch is over. But while we can’t fix our climate problems for free, the price signal sent through a cap-and-trade system will drive low-carbon investments in the most inexpensive and efficient way possible,” said Exelon CEO John Rowe in a speech (PDF) at the American Council for an Energy Efficient Economy’s national conference on Tuesday. “Putting a price on carbon is essential, because it will force us to do the cheapest things, like energy efficiency, first.”

Rowe said that inaction on climate was not an option—that if Congress did not act, the Environmental Protection Agency (EPA) would, the result will be “more arbitrary, more expensive, and more uncertain for investors and the industry than a reasonable, market-based legislative solution.”

“I am disappointed that Congressional Republicans and business groups can’t recognize this reality,” he said. “Because of their stridency against carbon legislation, Exelon has decided not to renew its membership in the U.S. Chamber this year.”

The chamber almost immediately contested Rowe’s allegations that it did not support efforts to reduce atmospheric greenhouse gas emissions, publishing a concrete position on climate change and emphasizing that the group had documents, letters to Congress, testimony, and policy recommendations to prove that it supported efforts to reduce greenhouse gas emissions in the atmosphere.

“Our position is simple: There should be a comprehensive legislative solution that does not harm the economy, recognizes that the problem is international in scope, and aggressively promotes new technologies and efficiency,” the business group of 3 million members said. “Protecting our economy and the environment for future generations are mutually achievable goals.”

The chamber’s president and CEO, Thomas J. Donohue, stressed however, that the response to climate change should include all major carbon dioxide–emitting economies, and that they should promote new technologies, emphasize efficiency, ensure affordable energy for families and businesses, and help create American jobs and return our economy to prosperity.

“These are mainstream, commonsense views that are shared by a broad majority of the American people, the business community, and a growing number of Democrat and Republican legislators,” he said.

Donohue said that the chamber did not support the Waxman-Markey bill that passed in the U.S. House this June, because it would not reduce the global level of greenhouse gases in the atmosphere. It was also not “comprehensive nor international, and it falls short on moving renewable and alternative technologies into the marketplace and enabling our transition to a lower carbon future,” he said.

Of even more significance, the cap and trade program proposed in the bill would likely impose carbon tariffs on goods imported into the U.S., which would almost certainly spur retaliation from global trading partners, he said.

Earlier in the week, PG&E withdrew its membership from the chamber, saying in a letter (PDF) that it was concerned about the group’s “extreme rhetoric and obstructionist tactics,” such as its much-publicized call to put the science behind the EPA’s endangerment finding on trial.

Albuquerque-based public utility PNM Resources said that because climate change was the most “pressing environmental and economic issue of our time,” it had decided it would be more productive by associating with organizations that shared that view.

Exelon, PG&E, and PNM Resources are all members of the U.S. Climate Action Partnership (USCAP). That alliance’s “Blueprint for Legislative Action” (PDF) formed the basis of the Waxman-Markey bill, as Congressmen Henry Waxman (D-Calif.) and Edward Markey (D-Mass.) have publicly stated.

Earlier this month, USCAP members Alstom and Duke Energy pulled out of the American Coalition for Clean Coal Electricity (ACCCE) because of its questionable support for climate legislation. As POWERnews reported, the ACCCE countered—much in the vein of the U.S. Chamber of Commerce—that it was against climate change legislation. It said that it was for carbon management—including a mandatory cap-and-trade program—as long as “effective cost-containment measures [are] a centerpiece of the legislation.”

Sources: Exelon, U.S. Chamber, PG&E, PNM, USCAP, POWERnews