Historically low interest rates are making some home buyers reconsider the conditions of their loans.

With rates at historic lows, potential home buyers now have a number of unexpected factors to consider when buying a house, namely the costs and benefits of 15-year and 30-year mortgages.

Both have their advantages and disadvantages. With a 30-year, there is more time and flexibility with payments, but higher lifetime payments and a higher interest rate. A 15-year mortgage has lower interest rates and a lower overall payment, but monthly payments are usually much higher.

How does the math add up? The New York Times, thankfully, completed an exploration of the loans’ pros and cons using the handy dandy mortgage calculator. Here are the highlights of the paper’s findings:

• A $300,000 loan would cost $1,475 a month for principal and interest over 30 years, versus $2,145 over 15 years, using a 4.25 percent rate on the 30-year and 3.5 percent on the 15-year.
• Tony Clintock, a regional sales leader for the Irving, Texas-based MetLife Home Loans, said the savings over the life of the 15-year mortgage would be $145,000; in addition, the principal would be reduced by $15,000 in the first year, compared with only $5,000 on a 30-year loan.
• And, remember those historic interest rates? According to Freddie Mac, 15-year mortgage rates are at 3.4 percent, more than three-quarters less than a 30-year. You could “shave 5, 7 or 10 years off their loan,” Clintock said.

In the end, though, it all comes down to income, said Robert Rauf, who works with Real Estate Mortgage Network in Manasquan, N.J.

“A lot of people cannot afford a 15-year mortgage,” Rauf said. And there are also supplementary costs to keep in mind, even if you have the income to consider a 15-year mortgage, said Karen C. Altfest, the executive vice president of Altfest Personal Wealth Management, in Manhattan.

But even if the costs prove too high, homebuyers can always consider refinancing down the road. According to CoreLogic, 53 percent of refinancing homeowners opted for a 15-year mortgage, an increase of more than 40 percent from 2007.