15 vs 30 Year Mortgage: the Payment Is the Real Decision
The 15-year saves $249,826 in interest. It also costs $635 more every single month, and that payment cannot be lowered in a bad year. Both facts matter equally, and only the first one gets quoted. The honest question is not which is cheaper - it is whether the higher payment is survivable for fifteen years.
Both numbers, together
A $320,000 loan. 15 years at 5.75%, or 30 years at 6.5%. shorter terms usually price lower, and that is part of the story.
| 15 year | 30 year | |
|---|---|---|
| Rate | 5.75% | 6.5% |
| Monthly payment | $2,657 | $2,023 |
| Total interest | $158,316 | $408,142 |
| Total paid | $478,316 | $728,142 |
The 15-year saves $249,826 of interest. That is a genuinely enormous number - more than three quarters of the loan itself.
It also costs $635 more every month, for fifteen years.
Both of those are the decision. Only the first one tends to get quoted.
Why the saving is so large
Two things compound together.
Half the years. Interest accrues on the balance, so fifteen fewer years of balance means far less interest - and a shorter loan pays the balance down much faster from the start.
A better rate. Shorter terms usually price around three quarters of a point lower. On a large balance over many years, that alone is worth a great deal.
The second point matters when comparing against paying extra on a 30-year: overpaying does not get you the better rate.
The risk that does not appear in the table
$2,657 a month is not a target. It is a requirement.
In a month when the car breaks and the boiler goes, it is $2,657. In a year when one income stops, it is $2,657. There is no facility to pay less because things got difficult.
That is the entire case against the shorter term, and it is not a small one. A mortgage payment you cannot reduce is the thing that turns a bad year into a crisis.
The middle path
Take the 30-year and pay extra voluntarily. From the extra payment calculator:
| Extra a month on the 30-year | Finishes in | Interest saved |
|---|---|---|
| $200 | 23.4 years | $105,429 |
| $500 | 18.0 years | $185,552 |
An extra $500 - $135 less than the 15-year demands - clears it in eighteen years and saves $185,552. That is about three quarters of the 15-year’s saving.
You give up the rest, mostly because of the rate difference. In exchange you keep a required payment of $2,023 and the ability to stop overpaying in any month you need to.
For most households that is the better trade. Not because the arithmetic is better - it is not - but because the flexibility is worth something real that the arithmetic cannot price.
How to decide
The honest test is not “can I afford $2,657?” It is:
Could I afford $2,657 in a bad year? One income gone for three months. A large unexpected bill. Both at once.
If yes, with room to spare, the 15-year is the better deal and the saving is genuine.
If it would be tight, take the 30-year and overpay. You end up in nearly the same place with a safety net you may never need - and would be very glad of if you did.
Two things worth checking
The actual rate difference. Get quotes for both. If the gap is small, the case for the shorter term weakens and paying extra looks better.
Whether you have an emergency fund. A 15-year payment with no savings behind it is a fragile arrangement. Fill that first - it matters more than the term.
Compare both on your own figures in the 15 vs 30 year calculator - it shows the payment and the total interest together, because that is the real decision.
Common questions about 15 vs 30 year mortgage
How much does a 15-year mortgage actually save?
On a $320,000 loan, $158,316 of interest against $408,142 - a saving of $249,826. That is a genuinely enormous number and it is why the shorter term gets recommended so often.
What does the shorter term cost month to month?
$2,657 against $2,023 - $635 more, every month, for fifteen years. Unlike a voluntary extra payment, that figure cannot be reduced in a month when money is tight.
Can I get most of the benefit without the commitment?
Yes. Take the 30-year and pay extra voluntarily. An extra $500 a month clears it in 18 years and saves $185,552 - around three quarters of the 15-year saving, while keeping the lower required payment as a safety net.
Do 15-year mortgages have lower rates?
Usually, yes - often around three quarters of a point lower. That rate advantage is real and it is part of why the interest saving is so large. Paying extra on a 30-year does not get you that better rate.
Which should I choose?
If the higher payment is comfortable with room to spare, the 15-year is the better deal. If it would leave you with no margin, take the 30-year and overpay when you can. The risk of a fixed high payment in a bad year is real and not worth taking lightly.