The 15-year fixed is a different animal than the 30-year. Lower rate. Faster equity. Massively less total interest. But in San Diego — where payments are already the national ceiling — committing to a 15-year payment requires either a strong income, a substantial down payment, or a modest home. For the buyers who can swing it, it's the highest-return choice in personal finance.
The Thesis in One Sentence
A 15-year fixed cuts lifetime interest by roughly two-thirds and eliminates the mortgage inside a typical working career — if you can carry the payment without gutting the rest of your financial life.
The math is uncontroversial. The behavior is where it gets complicated. On a $700,000 San Diego loan, a 15-year at 6.00% costs about $5,907 per month. The same loan on a 30-year at 6.75% is $4,539. That $1,368 monthly difference compounds — but so does the freedom it buys.
It's Not About Being "Smart"
Internet finance culture treats the 15-year as the obviously correct answer, and people who pick the 30-year as financially uninformed. That's wrong. The right term depends on income stability, investment alternatives, and what you'd actually do with the payment spread. Neither choice is a character test.
Who the 15-Year Is For
- Buyers whose 15-year payment still leaves housing DTI under 30%. If the faster term doesn't strain the budget, take it.
- Late-career buyers who want to retire mortgage-free. At 50, a 15-year finishes at 65 — perfect retirement alignment.
- High earners in stable industries. Physicians, attorneys, tenured faculty — anyone with predictable long-term income.
- Refinancers with substantial equity. If you're 10 years into a 30-year and refinancing, a 15-year can finish in nearly the same timeline as the original.
- Buyers who value being debt-free faster. This is a legitimate reason, not a soft one.
Who Should Think Twice
- Buyers stretching to afford the home. A 15-year payment that forces you to skip retirement contributions is a bad trade.
- Households with variable income. Commissioned sales, startup equity, freelance — avoid locking in a high mandatory payment.
- Buyers without 6 months of reserves after down payment. The 15-year offers less room for surprises.
- People who would invest the payment difference at higher after-tax returns. Rare in practice, but real.
Side-by-Side: 15 vs. 30-Year
Using an $800,000 San Diego loan as the baseline:
| Metric | 15-Year Fixed | 30-Year Fixed | Difference |
|---|---|---|---|
| Illustrative Rate | ~6.00% | ~6.75% | -0.75 pts |
| Monthly Payment (P&I) | $6,751 | $5,188 | +$1,563 / mo |
| Total Interest Paid | $415,180 | $1,067,680 | -$652,500 |
| Equity at Year 5 | $204,590 | $71,440 | +$133,150 |
| Equity at Year 10 | $489,200 | $167,120 | +$322,080 |
| Loan Paid Off | Year 15 | Year 30 | 15 years sooner |
The headline number is $652,500 — that's the lifetime interest savings on a single loan. At San Diego price levels, it's often more than most households will save for retirement in their entire careers.
The Forced-Savings Argument
Critics say a 15-year is just forced savings at the rate of your mortgage (6%). That's accurate — but forced savings at 6% is still a 6% guaranteed return, after-tax-equivalent, in a volatile world. For most households, that beats the realistic after-tax return on taxable investments.
What the 15-Year Gets You
Lower Rate
15-year rates run roughly 0.50-0.75 percentage points below 30-year rates. Lenders price them that way because they assume less inflation and rate risk. For identical principal, you're paying meaningfully less per dollar borrowed.
Fast Equity Buildup
In year one of a 15-year, roughly 40% of each payment goes to principal — versus just 15% on a 30-year. By year 5, your equity position is 2-3x what it would be on a 30-year. This matters if life requires you to sell or tap equity unexpectedly.
Payoff Inside a Working Career
Buy at 40, pay off at 55. Buy at 50, pay off at 65. No mortgage in retirement means your required income drops dramatically — which changes how much you need to save and when you can stop working.
Psychological Weight
Don't discount this. Knowing you will own your home outright in 15 years is structurally different from knowing you'll owe a bank until you're 70. It changes how you take career risks, start businesses, or ride out downturns.
What It Costs You
Higher Monthly Payment
Plan on 25-35% more per month than a 30-year on the same loan. On a $700K San Diego loan that's an extra $1,200-$1,500. If that money would come from retirement contributions, emergency reserves, or family needs, reconsider.
Less Flexibility
Job loss, medical event, or family emergency — the 15-year payment is still due. You can refinance if you qualify, but qualifying in a tough moment is much harder than when you're employed.
Higher DTI at Qualification
Because the required payment is higher, lenders use that higher number when calculating your DTI. You may need to buy a smaller home on a 15-year than on a 30-year with the same income.
The San Diego Context
San Diego's math makes the 15-year a minority choice, but not for bad reasons:
- Price levels: Median San Diego homes require $600K-$900K loans. 15-year payments on those balances cross $5,500-$8,500/month — workable for top-decile incomes but not mass-market.
- Refi migration: Many 15-year originations in San Diego are refinances after 5-10 years of paydown, not new purchases.
- Self-selecting buyers: 15-year buyers here skew older, higher-equity, and more likely to be move-up buyers rolling in substantial proceeds from a prior sale.
- Jumbo spread widens the case: On jumbo loans, the 15-year rate advantage is often 0.875 points or more — enough to tip the calculation further toward the shorter term.
The 15-year share of San Diego purchase originations has held around 6-8% since 2015. In refinances, it's closer to 18% — reflecting its real role as a mid-career equity acceleration tool rather than a first-purchase default.
CoreLogic · San Diego Market Report, Q1 2026
The Hybrid Strategy
For buyers torn between terms, here's a middle path that works for many San Diego households:
- Take the 30-year fixed. Lower required payment, maximum flexibility.
- Commit to a 15-year payoff schedule. Calculate what your payment would be on a 15-year, then send that amount voluntarily every month.
- Monitor quarterly. If income drops or a crisis hits, drop back to the 30-year required payment without refinancing.
- Reap most of the benefit. You'll pay off in about 15.5 years instead of exactly 15, and pay perhaps 5-10% more interest — in exchange for enormous flexibility if life turns.
This isn't as efficient as a true 15-year (you'll pay the higher 30-year rate on your balance), but the optionality is worth the small extra cost for most families.
When 15-Year Beats the Hybrid
- You have strong, steady income and don't need the flexibility
- The rate spread is exceptionally wide (over 0.75 points)
- You'd never realistically prepay a 30-year on your own
- Psychological commitment matters — you want the forcing function
The Bottom Line
The 15-year is mathematically superior for buyers who can absorb the payment without cracking. For everyone else, it's either the hybrid strategy or a straight 30-year. The worst outcome is picking a 15-year, discovering it's too tight, and then being stuck with it during a job change or family emergency. Honest affordability assessment matters more than the term itself.
Run the numbers on your specific situation — loan size, interest rates, and your realistic monthly cash flow after all other obligations. If the 15-year fits comfortably, take it. If it doesn't, the 30-year plus voluntary prepayment is an excellent second choice.