Environmental crusader and prominent Democrat Al Gore uses 20 times more electricity in his home than the average American, says a conservative U.S. think-tank.

The former U.S. vice-president and his family used nearly 221,000 kilowatt hours of electricity in their mansion in Nashville in 2006, according to utility bills brought to light by the Tennessee Center for Policy Research. Gore's bills added up to about $1,359 US a month.

The average American household uses about 10,656 kilowatt hours of electricity a year, the think-tank said.

"We wanted to see if he was living by his own recommendations and walking the walk," said Drew Johnson, the president of the think-tank, which researches public policy issues.

Johnson said his group got its figures from Nashville Electric Service. But company spokeswoman Laurie Parker told the Associated Press the utility never got a request from the policy centre and never gave it any information.

The Associated Press confirmed some of the bills, finding that the Gore household used 191,000 kilowatt hours for an 11-month period between Feb. 3, 2006, and Jan. 5, 2007.

The report was released Monday, a day after an Oscar was awarded to  An Inconvenient Truth, a documentary that chronicles Gore's fight against global warming — and takes some sharp jabs at the administration of President George W. Bush and the Republicans.

Reaction to the report immediately split along political partisan lines, with conservative commentators such as Rush Limbaugh pouncing upon it with glee, accusing Gore of hypocrisy, and left-wing bloggers denouncing it as a smear campaign by Republican supporters.

Gore's 930-square-metre home is about four times larger than the average American home built in 2006, according to the National Association of Home Builders.

The home is also powered by natural gas, the Tennessee Center for Policy Research said, noting that the Gore family spent $1,080 US a month on natural gas in 2006.

In the past, the think-tank's president has criticized  An Inconvenient Truth.

Gore subsidizes renewable energy: spokeswoman

A spokeswoman for Gore said Gore is being attacked for his green message.

"Sometimes when people don't like the message, in this case that global warming is real, it's convenient to attack the messenger," said Kalee Kreider.

She said Gore subsidizes renewable energy sources such as solar power, wind power and methane gas to balance 100 per cent of his electricity costs.

She said Gore participates in a utility program that lets people buy blocks of "green power" for $4 a month. Gore purchases 108 blocks a month, the equivalent of 16,200 kilowatt hours.

The Gore home is also under renovation to add solar panels, Kreider said.

"For every ton of carbon they emit, [Gore] offsets that by doing investments in renewable energy sources," Kreider said.

Johnson said this is not enough.

"In general, I applaud his efforts to reduce energy consumption, but if he is going to be a spokesman for global warming, he has to be willing to make the same sacrifices," Johnson said.

With files from the Associated Press