ReckonBoxThe choice the dealer makes you pick
Cash back and a low interest rate are two versions of the same discount, and almost every manufacturer lets you take one of the two. The rebate hands you money and you finance at the ordinary rate. The low APR cuts the rate and keeps the rebate. Which one costs less is rarely obvious from the headline numbers.
Take the default: a $35,000 car, $5,000 down, over 60 months. Take the $2,000 rebate and finance $28,000 at 6.9%, and the payment is $553.11. Take the 1.9% promotional rate on the full $30,000 and it is $524.52. Over the loan, the low rate totals $31,471 against the cash back deal's $33,187, so the low rate wins by about $1,716. The rate saved more interest than the rebate was worth.
When each one wins
A low APR wins when the interest it saves is larger than the rebate, and cash back wins when the rebate is larger than the interest saved. That balance shifts with three things: the size of the rate gap, the size of the rebate, and the length of the loan.
A wide rate gap, say 7% down to 0.9%, favors the low rate, because the saving compounds over every month. A fat rebate against a narrow gap favors the cash. And a longer term tilts toward the low rate, since it has more months to work, while a short loan gives it little time and lets a rebate come out ahead. The default flips to cash back if you raise the rebate to $8,000 and shrink the gap.
| $30,000 balance, 60 months | Cash back ($2,000 at 6.9%) | Low rate (1.9%) |
|---|---|---|
| Monthly payment | $553.11 | $524.52 |
| Total paid | $33,187 | $31,471 |
Why the rebate looks better than it is
A rebate is money now, which feels concrete, while saved interest is spread thin across five years, which feels abstract. That framing is why people reach for the cash. The arithmetic does not care about framing. The tool prices both deals to the last dollar and states the winner and the margin, so a $2,000 rebate that costs you $1,716 in extra interest shows up as the more expensive choice it is.
What this does not cover
This compares the financing on the price you enter. It leaves out sales tax and fees, which apply to both deals and so do not change the winner much, though a few states tax the price before the rebate and a few after, which nudges the margin. It also assumes you finance rather than pay cash, in which case a rebate is simply money off and there is no rate to compare. For the tax and fee side of either deal, the auto loan calculator carries those.
None of this says which deal to take. It shows what each one costs so the choice is yours, and a lender confirms the rate you actually qualify for.
Frequently asked questions
Should I take the cash back or the low interest rate? Take whichever costs less over the loan, which depends on the numbers. A rebate cuts the loan balance but you pay the ordinary rate; a low APR cuts the rate but you get no rebate. On a $30,000 balance over 60 months, a 1.9% rate versus 6.9% saves more than a $2,000 rebate, so the low rate wins. A big rebate against a small rate gap flips it.
Why can I not take both the rebate and the low rate? Because manufacturers structure them as competing incentives, and almost all let you choose one per vehicle, not both. The low APR is subsidized by the automaker in place of handing you the cash, so the two are alternatives. This calculator exists precisely because you have to pick, and the cheaper choice is not obvious from the headline numbers.
How does the rebate lower my cost? A rebate reduces the amount you finance, so you borrow less and pay interest on a smaller balance. A $2,000 rebate on a $30,000 loan drops the balance to $28,000, and both the payment and the total interest fall. The catch is that you finance that smaller balance at the ordinary market rate rather than the promotional one.
Does a longer loan term change which deal wins? Yes, because a longer term multiplies the value of a lower rate. The low APR saves interest on every month of the loan, so stretching from 36 to 72 months widens its advantage over a fixed rebate. A short loan gives the low rate less time to work, which is when a rebate is more likely to come out ahead.
Does this include sales tax and fees? No, it compares the financing on the price you enter, so tax and fees, which apply to both deals, are left out to isolate the rebate against the rate. Some states tax the price before the rebate and some after, which can shift the comparison slightly. For the tax and fees on either deal, the auto loan calculator handles those.