Should you refinance? The break-even calculation that matters

Refinancing is sold on the monthly payment, because the monthly payment is easy to make look good. It is the wrong number to optimise, and the reason is arithmetic rather than opinion.

The trap

Suppose you have 24 years left on a mortgage and you refinance into a fresh 30-year term at a lower rate. Your payment falls, sometimes substantially. Two things just happened, and only one of them was mentioned.

The rate fell, which genuinely saves money. And the term was reset, spreading the same balance over six additional years, which lowers the payment while increasing total interest. Depending on the numbers, the second effect can exceed the first, so the payment falls and the total cost rises.

A lower monthly payment tells you the term got longer, the rate got lower, or both. On its own it tells you nothing about whether you saved money.

The two calculations

Break-even on closing costs

Closing costs divided by monthly saving. If costs are $6,000 and you save $250 a month, that is 24 months to recover them. Move out before then and you have lost money on the transaction regardless of the rate.

Under about 24 months is comfortable. Beyond about 48 months, you are making a bet on staying put that most people lose.

Total cost over the full term

New payment × new term in months, plus closing costs, against current payment × months remaining. This is the number the monthly figure conceals, and it is the one that tells you whether refinancing made you better off.

Run both. They can disagree, and when they do the disagreement is the actual decision: a refinance that fails the total-cost test but passes break-even is a cash-flow trade, not a saving. That can still be the right choice if cash flow now matters more than cost later, but you should know which one you are choosing.

The four cases where it is usually worth it

• A materially lower rate on a similar term. Refinancing 24 years remaining into a 20 or 25-year term at a lower rate captures the rate improvement without resetting the clock. Rarely offered, usually available if you ask.
• Dropping mortgage insurance. If your equity has passed 20% through appreciation or paydown, removing mortgage insurance can be worth more than the rate change. This is the most commonly missed opportunity, because nobody writes to tell you your equity crossed the threshold.
• Getting out of an adjustable rate before it resets, where the certainty is worth paying for.
• Consolidating genuinely expensive debt, with the caveat below.

When it usually is not

When you might move within the break-even window. When you are deep into an existing mortgage, because most of the interest on a long amortisation is paid early and refinancing late resets you to the front of that curve. When the only benefit is a lower payment from a longer term. And when you are rolling unsecured debt into a mortgage without changing the behaviour that created it, which converts debt you could walk away from into debt secured against your home.

Getting a real number

Ask for a loan estimate rather than a rate quote. The rate is one line; the fees are where refinances differ. Compare the total cost of each offer, not the headline rate, and ask specifically whether costs are being rolled into the balance, because a "no cost" refinance is usually a financed cost.

Our refinance calculator runs both calculations from your own figures and shows the total alongside the monthly, which is the comparison that decides it.