15-Year vs. 30-Year Mortgage: The Real Cost Difference
Updated June 2026 · 7 min read
📑 Table of Contents
Choosing between a 15-year and 30-year mortgage is one of the biggest financial decisions you will make when buying a home. The 15-year saves you a fortune in interest. The 30-year gives you breathing room. Which is right? Let's look at the numbers.
The Numbers: $320,000 Loan at 6.5%
| 30-Year Fixed | 15-Year Fixed | |
|---|---|---|
| Interest rate | 6.5% | 5.75% (typically lower) |
| Monthly payment | $2,022 | $2,657 |
| Total interest paid | $408,000 | $158,000 |
| Total cost of loan | $728,000 | $478,000 |
| Interest savings | $250,000 saved |
The 15-year mortgage saves $250,000 in interest. But the monthly payment is $635 higher — that is real money every month for 15 years.
The Case for the 15-Year Mortgage
- Massive interest savings — A quarter-million dollars is enough to fund a kid's college education or buy a second home.
- Lower interest rate — Lenders typically offer 15-year loans at 0.5-0.75% lower than 30-year. You save on the rate AND the term.
- Forced discipline — The higher payment forces you to live below your means. In 15 years, you own your home free and clear.
- Faster equity build-up — More of each payment goes to principal from day one.
The Case for the 30-Year Mortgage
- Lower monthly payment — $635/month difference can fund your IRA, build an emergency fund, or cover childcare.
- Flexibility — You can always pay extra on a 30-year loan to effectively turn it into a 15-year. But you cannot pay less on a 15-year if money gets tight.
- You can invest the difference — Invest that $635/month at 8% for 30 years, and you would have roughly $950,000 — far exceeding the $250,000 in interest saved.
- Inflation works in your favor — $2,022 in 2055 will feel much cheaper than $2,022 today. Fixed payments get easier over time.
The "Invest the Difference" Math
This is the strongest argument for the 30-year. Take the 15-year payment of $2,657. On a 30-year, you pay $2,022 and invest the $635 difference each month. After 30 years at 8%:
- 15-year strategy: House is paid off in year 15. You then invest the full $2,657/month for the next 15 years. Final investment balance: ~$920,000.
- 30-year strategy: You invest $635/month for the full 30 years. Final investment balance: ~$950,000 + a paid-off house.
The 30-year + invest strategy edges ahead — but only if you actually invest the difference. Most people spend it.
How to Decide
💡 Choose the 15-year if:
The higher payment is comfortably under 25% of your take-home pay, you have a solid emergency fund, and you value the certainty of being debt-free sooner.
💡 Choose the 30-year if:
You want flexibility, plan to invest the difference, have variable income, or the 15-year payment would stretch your budget too thin.
The mathematically optimal path is the 30-year + disciplined investing. The emotionally optimal path depends on you. Neither is wrong — both beat renting forever.