When Does Mortgage Refinancing Really Pay?

"Since it costs money out of my pocket to refinance, how do I know whether or not I will end up saving money?"

To save money, you must stay in your house longer than the "break-even period" – the period over which the interest savings just cover the refinance costs. The larger the spread between the new interest rate and the rate on your existing loan, the shorter the break-even period. The more it costs to obtain the new loan, the longer the break-even period.

But beware! The break-even period is not the cost of the new loan divided by the reduction in the monthly mortgage payment. This widely used rule of thumb is a misapplication of the principle that when explaining something to the consumer one should "keep it simple." Simple is good, except when it’s wrong!