Extended warranty arithmetic

What is a vehicle service contract worth, on average? Not what it might pay out on the worst day — what it is worth across every way the next few years could go. That question has a precise shape in arithmetic, called expected value, and working it through is the clearest way to see what you're buying when you're offered an "extended warranty."

A note on the words first. A true warranty comes with the car, from the manufacturer, at no separate charge. What's sold as an extended warranty is usually a service contract: a separate agreement, sold for a price, promising to pay for certain repairs under certain conditions. The FTC's guide to auto warranties and service contracts explains the difference and what to read before signing.

The inputs, all illustrative

Every number below is a placeholder chosen for readable arithmetic. The probabilities in particular are not estimates of how often any car breaks — we don't have those for your car, and neither does a round number in an article. They exist to show the method. The final section tells you how to replace them.

• Contract price: $2,400
• Deductible per covered repair visit: $100
• Four possible outcomes over the contract's life, each assumed to be the only covered event if it happens: no covered repair, a minor one ($600), a major one ($2,500) or a severe one ($5,000)

Walking the calculation

On these placeholder inputs, the buyer pays $2,400 for coverage whose average payout is $755. The difference is the seller's costs, commissions and margin, plus a charge for carrying the risk. That gap isn't sinister; it's how every insurance-like product works. The question is only whether what you get for it — protection against the bad outcomes — is worth that much to you.

Stress-testing the placeholders

The obvious objection: the probabilities were made up. Fair. So be generous. Double the chance of every covered repair — 60% minor, 30% major, 10% severe, leaving no chance at all of a clean run.

Still under the $2,400 price. For the average to break even here, the contract would need to be priced near $1,510 — or the covered repairs would have to be larger, or more frequent than one per outcome, than we've assumed.

Now go the other way, toward what is often overlooked. Real contracts carry exclusions, wear-item carve-outs, maintenance-record requirements and claim reviews. If you believe a share of the claims you'd make would not be paid, multiply line C by the share you expect to be paid. At a placeholder 90%, $755 becomes $679.50. The contract's terms, not the brochure, decide what goes in that slot.

Why people still buy them, reasonably

Expected value describes the average over many possible futures. You will live exactly one. If the severe outcome — a $5,000 bill — would mean missing rent or taking on high-interest debt, then the arithmetic above understates what the coverage is worth to you, because a dollar lost in a crisis costs more than a dollar lost in a calm month. That is the legitimate case for any insurance: paying a predictable premium to avoid an unaffordable loss.

The competing option is to insure yourself. Put the $2,400 into a dedicated repair fund on day one. In the first two outcomes above, the fund pays the whole bill with money to spare; the major repair nearly empties it, leaving $100 to find; the severe one it covers about half. Our piece on sizing a repair fund works out a target from your own car's facts. The fund is only a real alternative if you would genuinely leave it alone.

Two practical traps change the numbers further. If the contract is folded into a car loan, you pay interest on the price for years; the add-ons that end up inside your loan computes what that does. And check who stands behind the contract, whether it can be canceled for a partial refund, and which shops it lets you use — the last point feeds directly into dealer service or independent shop.

Your own worksheet

To replace the placeholders, you need: the quoted price and deductible, from the contract itself; a list of what is and isn't covered, from the contract's coverage section; the realistic cost of the two or three biggest covered repairs for your car, from a shop quote; and your honest estimate of the chance of each over the contract's term, informed by your car's age, mileage and history. Then fill in the blanks.

If the last box is far below zero, you're paying mainly for peace of mind, and the size of that number is its price. Decide whether it's worth it with the figure in front of you, not the salesperson's worst-case story.