15-Year vs. 30-Year Mortgage: Which One Saves You More Money?

The Trade-Off in One Sentence

A 15-year mortgage costs less total interest and builds equity faster, but the monthly payment is significantly higher — typically 50-60% more. Whether that trade-off makes sense depends on your income, other goals, and risk tolerance.

The Numbers: $320,000 Loan at 6%

• 30-year: $1,919/month, total interest $371,000, paid off in 2056
• 15-year: $2,700/month, total interest $166,000, paid off in 2041
• Monthly difference: +$781/month
• Total interest saved: $205,000

That's a lot of money — but it comes with a real monthly budget impact.

When a 15-Year Mortgage Makes Sense

• You can comfortably afford the higher payment while still maxing out retirement contributions
• You want to be mortgage-free before retirement or before your kids start college
• You have a large enough emergency fund that a higher fixed obligation doesn't stress your finances
• You're buying well below what lenders approve you for

When a 30-Year Makes More Sense

• The lower payment gives you breathing room to invest more for retirement (where returns may exceed your mortgage rate)
• You live in a high-cost area where the 15-year payment would stretch your budget too thin
• Your income is variable or commission-based — a lower mandatory payment is safer
• You plan to invest the monthly difference in a diversified portfolio (the 'invest the difference' strategy)

The 'Invest the Difference' Strategy

Here's the counterintuitive math: if you take the 30-year mortgage and invest the $781/month difference at 7%, after 30 years you'd have about $954,000 — far more than the $205,000 in interest you 'saved' with the 15-year. Of course, this assumes you actually invest the difference every month and the market cooperates. Most people don't.

The Behavioral Reality

The 'invest the difference' strategy works beautifully on a spreadsheet. In real life, many homeowners spend the extra cash flow rather than investing it. The 15-year mortgage is a form of forced savings — you build equity automatically. If you're disciplined enough to invest the difference, the 30-year can win mathematically. If you're not, the 15-year wins in practice.

Refinancing: You Don't Have to Choose Forever

Starting with a 30-year and refinancing to a 15-year later is a common path. As your income grows and rates potentially drop, you can switch. You're not locked into one term for the life of the loan.

The Interest Rate Difference

15-year mortgages typically carry rates 0.5-1.0% lower than 30-year loans because they're less risky for lenders. This rate advantage compounds the interest savings beyond just the shorter term.

The Bottom Line

If you can afford the 15-year payment without sacrificing retirement savings or emergency funds, it's a powerful wealth-building tool that saves six figures in interest. If the higher payment would leave you house-rich and cash-poor, the 30-year is the smarter choice — especially if you invest the difference consistently.