A loyal General Motors' owner and the top Republican on the House Energy Committee, Joe Barton may soon have to take his Tahoe in for a trade.

A new requirement for Washington politicians is to go "green."

It's not a fancy SUV. Congressman Barton leases a Flex-Fuel Chevy Tahoe, which is made in Arlington, for what he calls official use only.

"It's got an 8 cylinder engine," he said.

He spends about $700 a month in taxpayer money on the lease. Using ethanol, it gets about 21 miles per gallon on the highway.

"For not being a hybrid, that's as good as it gets," he said.

But that may not be good enough. He might have to trade it in for a hybrid due to a little-known amendment in last year's energy bill. The amendment requires members of Congress who lease vehicles at taxpayer expense to drive only "low greenhouse gas emitting vehicles."

So far, the Environmental Protection Agency has not issued a list of those cars, although only hybrids have received good grades in the EPA's Green Vehicle Guide.

"And I think that's one of the reasons I voted against it, because it's too vague," he said.

Missouri Congressman Emanual Cleaver authored the amendment.

"It's a poor example for us to spend so much time and money talking about energy independence and presenting to the people an image of fat cats living the fat life," Cleaver said.

About 130 of the 435 members of Congress lease vehicles at taxpayer expense. They will all have to comply with the amended energy bill by using only "low greenhouse gas emitting" vehicles.

The EPA's list should be out later this year.

E-mail jbrady@wfaa.com