A growing number of homeowners are choosing to pay down their mortgages at a faster rate--even if it means a substantial jump in their monthly payments.

Between January and June, 26% of homeowners who refinanced chose a 15-year fixed-rate mortgage, according to data from CoreLogic, a provider of financial, property and consumer information. During all of 2009, 18.5% of borrowers who refinanced opted for a 15-year term.

What's prompting the shift to shorter loans? Historically low interest rates for fixed-rate mortgages.

Homeowners are doing the math and realizing that rates have fallen enough so the increase in payment between a new 15-year mortgage and their current loan is no longer unbearable for their budgets, says Bob Walters, chief economist at online lender Quicken Loans.

The average rate on a 15-year fixed-rate mortgage was 3.86% for the week ending Aug. 26, according to Freddie Mac's weekly survey of conforming mortgage rates.

A Change in Thinking
The financial situation of those capable of refinancing today is a factor in the shift, Mr. Walters says. These people typically are homeowners with the best credit and the most equity -- and, therefore, most suited for a shorter-term loan.

But there might be some other psychology at work. "We're seeing a different view on debt than maybe we've seen in the past," he says. Today, homeowners are saying, "I really want to pay this off. I'm going to bite the bullet and take the payment and work toward paying this down."

A 15-year mortgage also acts as somewhat of a forced savings account for homeowners, says Leif Thomsen, chief executive of Mortgage Master, a privately owned lender, given that the higher payments help a borrower pay down the principal at a quicker clip.

This is a huge shift in borrower thinking. "There was a drive a couple of years ago to take out the biggest mortgage that you could and use all of the money you would have otherwise had in the house and put it into stocks and bonds--to think of your house and mortgage as part of your entire investment portfolio," says Amy Crews Cutts, deputy chief economist for Freddie Mac.

"That worked for people who do investment finance for a living and are good at managing accounts," she says. "But for the average person, debt is a drag on their psyche as well as their overall budget." Many Americans have reverted to the goal of paying off their house and getting rid of their mortgage, Ms. Cutts adds.

Doing the Math
Refinancing into a shorter-term mortgage isn't a strategy for everyone, however.

Choosing a shorter term usually means you'll get a better rate--and you'll pay much less interest over the life of the loan--but a shorter time frame ramps up monthly mortgage payments.

For example, with a 4.5% interest rate on a 30-year fixed-rate mortgage of $200,000, you would have a monthly payment of $1,015, including principal and interest, Ms. Cutts says. The monthly payment jumps to about $1,480 with a 4% interest rate on a 15-year fixed-rate loan.

Of course, if the refinancing borrower's current 30-year loan has a higher rate, the difference between the monthly payments could be lower. Still, you should count on some increase in monthly payments.

In general, Mr. Walters says, those who choose 15-year fixed-rate mortgages are older and have more equity and less debt than other folks. They also earn higher incomes and don't have some of the added expenses that younger homeowners typically do.

"People who are taking these loans are financially stable and can afford the payments, but at the same time are planning on staying in their home for an extended period of time," Mr. Thomsen says.

Mr. Walters says you shouldn't take on a 15-year fixed-rate mortgage unless you have substantial savings, including at least a year's worth of living expenses in liquid accounts.

Also, he recommends having a debt-to-income ratio below 35%. So if you have a gross salary of $5,700 per month, for instance, your monthly debt--including any mortgage payments, taxes, insurance, homeowners-association dues as well as auto and student loans and credit-card debt--would have to be a max of $1,995 to get a 35% ratio.