The Numbers Side by Side
Assume a $320,000 loan (after 20% down on a $400,000 home) at 6.5% annual rate:
| Metric | 30-Year | 15-Year |
|---|---|---|
| Monthly Payment | $2,023 | $2,790 |
| Total Interest Paid | $408,280 | $182,116 |
| Total Amount Paid | $728,280 | $502,116 |
| Interest Savings | — | $226,164 saved |
The 15-year loan costs $767 more per month but saves over $226,000 over the life of the loan.
Why the 30-Year Loan Costs So Much More
Interest compounds over time. With a 30-year loan, you're paying interest on the remaining balance for twice as long. In the early years, the vast majority of each payment goes toward interest rather than principal — meaning you build equity extremely slowly.
In the first year of a 30-year loan at 6.5%, roughly 85% of your payment is interest. Only about $250 of your $2,023 payment reduces your actual loan balance each month at first.
When a 30-Year Mortgage Makes Sense
- Your budget is tight and you need the lower monthly payment to qualify
- You plan to invest the payment difference aggressively (and consistently earn more than 6.5%)
- You may sell or refinance within 7–10 years
- You're buying in a high cost-of-living area and need maximum purchasing power
When a 15-Year Mortgage Makes Sense
- You can comfortably afford the higher payment without straining your budget
- You want to be debt-free faster (especially before retirement)
- You prioritize guaranteed savings over market-dependent investment returns
- You're refinancing and want to reset your payoff timeline
The "Invest the Difference" Argument
Some argue you should take the 30-year loan and invest the $767 monthly difference in the stock market. Historically, the S&P 500 returns ~10% annually, well above a 6.5% mortgage rate. In theory, this wins.
In practice, most people don't actually invest the difference — they spend it. If you have strong investment discipline, the math may favor the 30-year loan. If not, the forced savings of a 15-year mortgage is the safer bet.
20-Year: The Middle Ground
A 20-year mortgage is often overlooked. At the same 6.5% rate on $320,000, the monthly payment is about $2,390 — just $367 more than the 30-year — but total interest drops to around $253,000, saving $155,000 vs. the 30-year loan. A good compromise if the 15-year payment feels too aggressive.
Hidden Costs to Factor In
- PMI: If your down payment is less than 20%, you'll pay private mortgage insurance (~0.5–1.5% of loan/year) until you reach 20% equity.
- Property taxes & insurance: Often escrowed by lenders. Add $300–800/month depending on your area and home value.
- HOA fees: If buying a condo or in a planned community.
- Maintenance: Budget 1–2% of home value per year for repairs.