Put more down or invest the difference? The math at 7% rates
At 7% mortgage rates, every dollar you put toward a down payment earns a guaranteed 7% return by avoiding interest. Here is how that compares to investing the same money — and when each choice wins.
At 3% mortgage rates, the math strongly favored investing surplus cash rather than paying down the mortgage — the stock market's historical 7–10% return easily beat the 3% cost of mortgage debt. At 7% rates, that gap has closed to nearly nothing. Here is how to think through the decision at current rate levels.
The guaranteed return of a larger down payment
Every dollar you put into a down payment earns a risk-free return equal to your mortgage rate. If your rate is 7%, putting an extra $20,000 down saves you $1,400/year in interest — a guaranteed, after-tax-equivalent 7% return on that $20,000. No investment earns a guaranteed 7%.
The stock market has historically returned 7–10% annually, but that is an average with enormous variance. In any given 5-year window you might earn 3% or 15%. The mortgage interest saving is certain. This is what makes the comparison genuinely close at 7%+ rates.
The PMI elimination threshold
The clearest win for a larger down payment is crossing the 20% threshold and eliminating PMI. PMI typically costs 0.3%–1.0% of the loan per year. On a $360,000 loan (80% LTV on a $450,000 home), PMI at 0.65% adds $195/month — $2,340/year. Putting in another $20,000 to reach 20% down eliminates that $2,340/year immediately, a return of 11.7% on the extra $20,000. That beats almost any risk-free alternative.
10% down → keep $45K invested
20% down → no PMI
$450,000 home price. 20% down = $90,000. 10% down = $45,000 + $45,000 kept invested.
The 20% scenario saves $551/month in housing costs ($2,914 vs $2,363). Over 5 years that is $33,060 in cash flow saved. The 10% scenario has $45,000 invested, which grows to roughly $63,000 at 7% — a $18,000 gain. On a pure 5-year comparison, 20% down wins by about $15,000 even assuming a solid investment return.
When investing wins
The math shifts if your mortgage rate is lower than your expected investment return after tax, and especially if you are below the PMI threshold by enough that crossing it requires a very large additional contribution. The scenarios where keeping cash invested tends to win:
- Your mortgage rate is below 5% (refinanced, assumed, or VA/USDA loan)
- You already have 20%+ down and are considering an even larger payment
- You have no emergency fund — liquidity has real value
- You have high-interest debt (credit cards, personal loans) that should be paid first
- Your employer offers a 401(k) match you are not yet maximizing
The liquidity trap most buyers ignore
Home equity is illiquid. A dollar in your down payment cannot be accessed without a refinance, HELOC, or sale — all of which have costs and delays. A dollar kept in a brokerage account can be accessed in 2 business days. For buyers who do not have a robust emergency fund (3–6 months of expenses), concentrating additional cash into a down payment is a risk that is easy to underestimate until an unexpected expense arrives.
The practical hierarchy most financial planners recommend: emergency fund first, employer match second, high-interest debt third, then the mortgage-vs-invest decision for surplus cash.
See the rent-vs-buy version of this trade-off
The rent vs buy calculator models the opportunity cost of tying up a down payment directly — you can see how invested down payment growth compares to home equity at each year of a chosen horizon.
Common questions
Is a bigger down payment always better?
Not always. A larger down payment reduces your loan balance and eliminates PMI, but the dollars go into an illiquid asset. If your mortgage rate is 7% and your investment alternative returns more than 7% after tax, the math favors investing the extra cash. The problem is that investment returns are uncertain and a mortgage payment is fixed — so most buyers choose the certainty of lower debt.
Does putting more down reduce the interest rate?
Slightly, through loan-level price adjustments (LLPAs). Going from 10% down to 20% down typically improves your rate by 0.1–0.25% at the same credit score. The bigger benefit of 20% down is eliminating PMI, not the rate improvement itself.
What is the minimum down payment for a conventional loan?
Conventional loans allow as little as 3% down for first-time buyers through programs like Fannie Mae's HomeReady and Freddie Mac's Home Possible. Standard conventional loans require 5% down. FHA loans allow 3.5% with a 580+ credit score. Below 20% always triggers PMI on conventional loans.
How long does it take to save a 20% down payment at current prices?
On a $400,000 home, a 20% down payment is $80,000. Saving $1,500/month takes roughly 4.5 years, assuming 4% annual return on savings. In high-price markets ($700K–$1M), the timeline stretches to 7–12 years, which is why so many buyers accept PMI rather than wait.