Down Payment Size Trade-Off
Example: Purchase price: 35000 $ · Smaller down payment: 10 % · Larger down payment: 30 % · Loan APR: 7.5 % · Loan term: 5 yrs · If invested, return: 6 %/yr
| Net advantage of larger down | $-952 |
| Interest saved (larger down) | $1,416 |
| Opportunity cost of that cash | $2,368 |
| Verdict (1=larger down, 0=keep cash) | 0 |
Worked example
On a $35,000 car, going from 10% to 30% down puts an extra $7,000 toward the purchase. At 7.5% over 5 years that saves roughly $1,500 in interest — but the same $7,000 invested at 6% could grow about $2,400. Here, keeping the cash to invest edges ahead, assuming you actually invest it.
Frequently asked questions
When is a larger down payment better?
When the loan rate is high relative to what you can safely earn investing, or when a bigger down payment avoids being underwater or unlocks a lower rate. High APRs tilt the verdict toward putting more down.
What is the risk of keeping cash to invest?
Investment returns are uncertain, while the interest saved is guaranteed. The strategy only pays off if you truly invest the money rather than spend it — and if your returns beat the loan rate over time.
Does a bigger down payment lower my rate?
Sometimes lenders offer better rates at higher down payments or lower loan-to-value ratios. If so, the interest savings are larger than modeled here, strengthening the case to put more down.