Why Extra Payments Are So Powerful
Most of your early mortgage payments go to interest, not principal — that's how amortization works. On a $320,000 mortgage at 6.5% for 30 years, your first payment of $2,023 includes $1,733 in interest and only $290 of principal. Every extra dollar you pay goes straight to principal, wiping out that disproportionate interest load early.
On a $320k loan at 6.5%/30yr: standard total interest = $408,807. With $200/mo extra: total interest = $350,290 — a saving of $58,517 and 5 years 8 months shorter payoff.
5 Strategies Ranked by Impact
- 1Round up every payment — pay $2,100 instead of $2,023. Small, painless, adds up to roughly one extra payment per year.
- 2Make one extra principal payment per year — a single $2,000 lump sum annually saves ~$30k on a $320k loan at 6.5%.
- 3Switch to bi-weekly payments — you make 26 half-payments instead of 12 full ones, effectively paying one extra monthly payment per year automatically.
- 4Apply windfalls directly to principal — tax refunds, bonuses, inheritance. Mark payments as 'principal only' with your lender.
- 5Recast your mortgage — after making a large lump-sum payment, ask your lender to re-amortize at the same rate. Monthly payment drops but term stays the same. Fee is usually $200–$500.
When You Should NOT Pay Off Early
Paying down a 6.5% mortgage is guaranteed 6.5% return (after-tax: closer to 5–6% once you lose the mortgage interest deduction). Compare that to your alternatives:
| Action | Expected return | Risk |
|---|---|---|
| Pay off mortgage early | 6.5% (mortgage rate) | None — guaranteed |
| Max out 401(k) with employer match | ~100% immediate on matched portion | Market risk |
| Max out HSA | Tax-free growth + deduction | Low (investment risk) |
| Pay off credit card at 20%+ | 20%+ guaranteed | None |
| Invest in S&P 500 index fund | 7–10% long-run average | Market risk, volatile |
1. Emergency fund (3–6 months expenses) 2. 401(k) up to full employer match (free money) 3. Pay off high-interest debt (>7%) 4. Max HSA if eligible 5. Extra mortgage payments 6. Max 401(k) / IRA 7. Taxable investing
The Recast vs Refinance Decision
If you come into a large sum — inheritance, business sale, stock vest — you have two options:
| Option | Cost | Rate changes? | Best when |
|---|---|---|---|
| Recast | $200–$500 fee | No — keeps existing rate | Your current rate is already low; you just want a lower payment |
| Refinance | 2–5% of loan | Yes — resets to market rate | Rates have dropped significantly since you bought |
Refinance if rates dropped more than 0.75% and you'll stay 3+ years. Recast if you want a lower payment without the cost and hassle of a full refinance.
$100 vs $300 vs $500 Extra: The Exact Payoff Table
Here's what each level of extra monthly principal does to a $350,000 mortgage at 6.5% for 30 years (base payment $2,212/month, baseline total interest $446,300):
| Extra/month | Payoff time | Time saved | Total interest | Interest saved |
|---|---|---|---|---|
| $0 | 30 yrs 0 mo | — | $446,300 | — |
| $100 | 27 yrs 3 mo | 2 yrs 9 mo | $398,900 | $47,400 |
| $300 | 23 yrs 2 mo | 6 yrs 10 mo | $330,800 | $115,500 |
| $500 | 20 yrs 4 mo | 9 yrs 8 mo | $285,300 | $161,000 |
The first $100/month saves $47,400 — $474 of interest per dollar of monthly commitment. The jump from $300 to $500 still saves $228 per dollar. Early extra payments do the heaviest lifting: $100/month for just the first 10 years, then nothing, still cuts about 21 months and $36,000 off the loan.
An unmarked extra $500 may be applied as a prepayment of next month's scheduled payment — interest included — which saves you almost nothing. Every lender has a principal-only option; use it, and verify the balance dropped on your next statement.
Invest or Prepay? The Break-Even Logic
Prepaying a 6.5% mortgage is a guaranteed, risk-free 6.5% return. Investing the same dollars in stocks has a higher expected return (~7% real, ~10% nominal long-run) but no guarantee. The honest comparison is your mortgage rate vs a risk-adjusted investment return:
| Your mortgage rate | Rational default | Why |
|---|---|---|
| Under 4% (2020–21 refi) | Invest — don't prepay | Even Treasury yields (~4.3% in 2026) beat your rate risk-free |
| 4–5.5% | Genuine toss-up | Prepaying ≈ bond returns; choose by temperament and timeline |
| 6–7%+ (2023–26 loans) | Prepaying is very defensible | A guaranteed 6.5% beats the ~4.5% risk-free rate by 2 points; stocks beat it only on average, with 20–35% drawdowns en route |
Prepay a 6.5% mortgage: $161,000 of guaranteed interest saved, house paid off in ~20 years. Invest $500/month at 7%: about $260,000 — $99,000 more, but only if you stay invested through every crash and actually earn the average. At a 4% return the investment path yields $183,000; the gap nearly closes. Higher mortgage rate = smaller reward for taking market risk.
Four Situations Where Prepaying Is a Mistake
- 1You have credit card or other debt above ~8% — paying 6.5% mortgage principal while carrying a 22% card balance burns money at 15.5% per year on every misallocated dollar
- 2You're skipping the 401(k) match — a 50% match is an instant 50% return; no 6.5% guaranteed return justifies leaving it
- 3Your emergency fund is under 3 months of expenses — mortgage prepayments are one-way; you can't withdraw principal back in a job loss without refinancing or selling
- 4Your rate is under ~4.5% — in 2026 you can earn more in a high-yield savings account (4.0–5.0% APY) with zero risk and full liquidity than you save by prepaying a 3.5% loan
Ten years of $500/month extra builds equity, but if you lose your job in year 11, the bank still wants the full $2,212 next month — home equity doesn't pay bills. If payment flexibility matters, keep the extra money in savings/investments until you can pay the loan off entirely, or use a recast ($200–$500 fee) to convert a lump sum into a permanently lower required payment.