SAN DIEGO —— As many as 18,000 households in the San Diego area would be added to the pool of would-be homeowners who could afford to buy a median-priced home if Congress changes loan limits for federally backed mortgages, according to report by the California Association of Mortgage Brokers released Thursday.

Borrowers for these "conforming" loans must qualify under guidelines set by Fannie Mae and Freddie Mac, which currently limit the size of mortgages —— $359,650 in 2005 for an owner-occupied, single-family home. As a result, local buyers most often must resort to so-called jumbo loans or to other kinds of mortgages instead of the lower-interest conforming loans.

The median-priced home in North County in June was $631,500, according to the North San Diego County Association of Realtors.

The difference between jumbo and conforming loans is significant, said Michael Faust, Government Affairs Committee chairman of the association and one of the authors of the report. In San Diego County, a $525,000 jumbo mortgage would require a $150,080 qualifying annual income; if the same amount could be borrowed as a conforming loan, the qualifying income would drop to $143,400.

"The limit for conforming loans is adjusted every year, but you have to remember that it is based on a national number," Faust said.

"In places like California, home buyers in the major cities don't have an opportunity to get Fannie Mae- and Freddie Mac-backed loans," he said.

Legislation approved by the House Financial Services committee and likely to be taken up by the Senate later this year would allow conforming loan limits in high-cost housing markets such as the San Diego area to be pegged at 150 percent of the nationwide limit.

"That will give an additional 18,000 people in the region a chance to qualify for conforming loans," Faust said. And the conforming loans' lower interest rates will mean that home buyers in the San Diego region "will save about $86 million."

"It makes a lot of sense," University of San Diego economist Alan Gin said.

"Housing prices vary drastically across the country, and especially in places like California's coastal cities, there would be a real benefit to locally set limits" on conforming loans, he said.

Meanwhile, Faust said the idea of different maximum limits for different parts of the country is not new.

"We're not talking about a crazy, outside-the-box idea here," he said. Alaska, Hawaii and Guam already have a limit that is 50 percent higher than the mainland United States.

Contact staff writer Edmond Jacoby at (760) 739-6675 or ejacoby@nctimes.com.