I bought a $400 vacuum cleaner two years ago and the cashier at Best Buy spent a solid three minutes trying to sell me a $79 extended warranty. “If anything goes wrong in three years, we replace it.” I almost said yes. Then I did the math in the parking lot and it made me angry.

Extended warranties are, for most products, a terrible deal. The retailers push them because the profit margin is enormous — often 50% or higher. The actual chance you will use the warranty is low, and even when you do, there are exclusions and deductibles. Here is why you should almost always say no, and the two exceptions where a warranty actually makes sense.

The retailer math (why they push it so hard)

Best Buy makes more profit from extended warranties than from the actual products. Think about that. A television that costs the store $400 and sells for $500 has a 20% margin. But a $100 warranty on that TV? The store keeps $50-$60 of that, pure profit. That is why the cashier is trained to mention it three times and not take no for an answer.

Consumer Reports has studied this for decades. Their conclusion: products rarely break during the extended warranty period. Most defects show up in the first 90 days (covered by the manufacturer warranty) or after several years (when the extended warranty has already expired). The warranty window is designed to cover the period when products are statistically least likely to fail.

The credit card perk you probably already have

Many credit cards — especially Visa Signature, World Mastercard, and American Express — automatically double the manufacturer’s warranty for free. If your vacuum has a one-year warranty, your credit card extends it to two years. You just have to have bought it with that card.

This is not advertised because the credit card companies benefit when you do not know about it. Check your card’s benefits guide. If it includes “extended warranty protection,” you are already covered. You just paid with the card. That is it. No $79 at the register.

The two times a warranty makes sense

Laptops for students. Kids spill things. They drop things. A laptop that gets carried in a backpack every day has a much higher failure rate than a desktop sitting on a desk. AppleCare+ for a MacBook that a teenager is taking to school is probably worth it. The accidental damage coverage is what you are really paying for — not the extended warranty itself.

High-end refrigerators. Modern fridges with ice makers, water dispensers, and smart screens have a lot of things that can break. Repair calls for those run $200-$400 minimum. If you are buying a $2,500+ refrigerator, a warranty from a reputable company (not the retailer — go through the manufacturer or a third party like SquareTrade) can pay for itself with one service call.

What to do instead of buying the warranty

Take the money you would have spent on the warranty and put it in a savings account. If you buy five appliances or electronics in a year and skip the warranty on each one, you have saved $250-$500. That is your self-funded warranty. If something breaks, you have the cash to fix or replace it. If nothing breaks — which is the most likely outcome — you keep the money.