Homeowners who have been thinking about refinancing, or who should have been, should get a move on. Interest rates are climbing and seem likely to keep going up.

The basics of any refinancing decision are pretty simple. If you’ll have the new loan long enough for its lower payment to offset the refinancing costs, the move generally pays.

But interest rates, investment returns, inflation and other considerations change pretty often. So let’s see how refinancing looks today, using the BankingMyWay Refinance Breakeven Calculator. In fact, a borrower who can achieve only a small interest-rate reduction may do better by prepaying principal on the old loan rather than sinking cash into closing costs for a new one.

If you got a 30-year fixed-rate mortgage 10 years ago you may be paying more than 8%, and refinancing at today’s rates, typically a little more than 5%, could save you a bundle.

Or could it? After all, you have 10 years of payments behind you. Refinancing to a new 30-year loan would mean 30 more years of payments instead of 20, offsetting savings from the lower rate.

Let’s assume we're dealing with a 30-year loan for $200,000, with 20 years to go and an interest rate of 8.3%. And we’ll figure on a new 30-year loan at 5.3%. The new loan is for $176,515, the balance remaining on the old loan after 10 years of payments.With the chart selection on “Monthly Payment Breakdown,” the calculator says the new payment would be $1,054, compared to $1,593 on the old loan. The “Breakeven points” chart says it would take about nine months for the monthly savings to offset $4,330 in closing costs.

But the more relevant figure is on the yellow bar, showing a 14-month breakeven point. This accounts for the fact that the new loan’s lower interest rate would reduce the mortgage-interest deduction on your federal income tax return. So your monthly savings would be a little smaller than it first appeared, and breaking even would take six months longer. Still, the refinancing looks like a pretty good deal.