TAMPA - Lawmakers are considering extending the first-time homebuyer tax credit a year to further boost the real estate market.

A survey by Zillow.com shows the credit would sway some buyers but that most who qualify would purchase anyway. The extension would come at a big cost: As much as $14.86 billion in tax revenue would go uncollected, according to Zillow.

The $8,000 first-time homebuyer tax credit runs through Nov. 30. Congress is considering everything from doing nothing to extending it six months to a year.

Some lawmakers want to extend the amount of the credit to $15,000; some want the extension broadened to include all homebuyers.

Nearly 1 in 5, or 18 percent, of prospective first-time homebuyers who participated in the survey said extending the tax credit would be the primary influence on their decision to buy a home before the end of 2010.

That would mean, according to Zillow estimates, that the extension would persuade 334,000 buyers to purchase a home during the next year.

"It doesn't sound like a lot, but it is a meaningful number to annual home sales," said Stan Humphries, chief economist at Zillow.com. "With these new buyers, we could see as much as a 5 percent increase from this year. Without them, sales could be down by as much as 2 percent."

Zillow surveyed more than 2,000 adults across the country who qualify as first-time homebuyers. Thirty-one percent of respondents said the tax credit would have no influence on their decision.

Reporter Shannon Behnken can be reached at (813) 259-7804.