0% financing vs. cash: which offer actually costs less?

First compare the two out-the-door prices

Manufacturers sometimes offer either promotional financing or a cash rebate, not both. Get a written out-the-door price for each path. A 0% rate on a higher price is not automatically better than a normal-rate loan or cash purchase with a large discount.

Separate guaranteed savings from assumed returns

Avoided loan interest is known once the contract is signed. Investment returns are uncertain and may be taxable. If you compare financing with investing the retained cash, use a return that matches the investment's risk and your actual behavior—not a best-case stock-market average.

Also test a zero-return scenario. It shows whether the financing offer is attractive even if the retained cash simply stays liquid.

Check every condition attached to the promotion

Promotional financing may apply only to certain trims, inventory, credit tiers, down payments, or shorter terms. Confirm whether there is an origination or documentation charge and whether the quoted price already assumes incentives that cannot be combined.

Liquidity has value, but debt changes behavior

Keeping cash can preserve an emergency fund and reduce the chance that an unexpected expense goes on a high-rate credit card. On the other hand, financing is not helpful if the retained cash is spent rather than saved or invested. Model the plan you will follow, not the plan that looks best in a spreadsheet.

A useful comparison sequence

Compare out-the-door prices, verify promotion eligibility, calculate each loan's total cash flow, preserve an adequate emergency reserve, and then test a conservative return on any genuinely retained cash. The cheaper result should survive more than one return assumption before investment growth becomes the deciding factor.