Refinancing a mortgage means swapping your current loan for a new one, usually to get a lower rate. Lenders love pitching it, because a refinance is a new loan and new loans earn them fees. Whether it's good for you comes down to three numbers: the monthly saving, the closing costs, and how long you'll stay. Let me walk through a real example.
A worked example
Say you owe $280,000 at 7.25% with 27 years left on the loan. That costs $1,971.74 a month.
Rates have dropped, and you can refinance to 6.0% over a fresh 30 year term. The new payment is $1,678.74 a month. That's a saving of $293.00 every month, since $1,971.74 minus $1,678.74 is $293.00. On paper it looks like an easy yes.
But refinancing isn't free. Closing costs on this deal run $5,000. So the real question is how long it takes the monthly savings to pay back that upfront hit.
The break-even test
Divide the closing costs by the monthly saving and you get the break-even point. Here, $5,000 of costs against $293.00 a month works out to 18 months. Stay in the house past month 18 and every month after that is genuine profit. Sell or refinance again before then and you paid $5,000 to lose money.
This is the test that actually matters. Not "is the rate lower" but "will I still be here when the closing costs have paid for themselves". If there's any real chance you'll move within the break-even window, the refinance is a bad bet no matter how good the rate looks. Our refinance calculator runs this exact comparison for your own numbers, break-even included.
The term extension trap
Notice something sneaky in the example. The old loan had 27 years left. The new one runs 30. You've quietly signed up for three extra years of payments, and that's where a lot of refinances go wrong. A lower rate stretched over a longer term can mean more total interest, not less, and the shiny monthly saving hides it.
In this particular case the numbers still work. Even after restarting the clock at 30 years, lifetime interest ends up about $29,498 lower than riding out the old loan. The rate drop is big enough to overcome the extra years. But that's a result you check, not one you assume. Run both loans full term through our mortgage calculator and compare total interest, not just the payment.
There's a behavioural catch too. The lifetime saving assumes you do something useful with the $293 a month, or at least don't fritter the extra three years of payments away. If the lower payment just becomes invisible extra spending, and you stay the full 30 years, the term extension quietly claws back a chunk of the win. If you want the best of both, refinance to the lower rate but keep paying the old $1,971.74. You'll clear the loan years early and the saving is all real.
Rules of thumb that hold up
A rate drop of about 0.75% to 1% is usually where the maths starts to clear the closing costs for a typical balance. Below that, the break-even stretches out and the deal gets marginal fast. Above it, you're normally in good shape, but check anyway.
And staying past break-even is the real test, always. The rate drop gets the headlines. The break-even decides whether you actually come out ahead.
One more thing to watch: "no closing cost" refinances. The costs don't vanish, they get rolled into the loan balance or baked into a slightly higher rate. That can still be a fine deal if you might move soon, since there's no upfront money to recover. But it's a repackaging, not a discount, and you should run it through the same comparison as any other offer rather than taking the label at face value.
My take
Refinancing makes sense when three things line up: a meaningful rate drop, a break-even you'll comfortably outlast, and a plan for the monthly saving that isn't "absorb it into the food shop". When those hold, take the deal without guilt. When they don't, a lower monthly payment is just a longer, more expensive loan wearing a nicer outfit.