Paul Sakuma, AP
FILE - This July 30, 2008, file photo, shows credit card stickers posted at a bowling alley in Palo Alto, Calif. Debit card use has been catching up to credit cards for years, but only recently amid a weak economy has debit become the big U.S. revenue driver for card processors. The bill overhauling the credit card industry is being touted as long-needed relief for overburdened consumers. But that doesn't mean paying your monthly bill will suddenly be a cake walk. (AP Photo/Paul Sakuma)

SALT LAKE CITY — Is it prudent or a big waste of money to purchase an extended warranty plan? For most people the answer to that question depends on the cost of both the plan and the purchase it’s intended to cover as well as the likelihood that the item being bought will malfunction. What it should depend on, however, is the type of credit card you’re using.

Each of the major card networks — Visa, MasterCard, American Express and Discover — offer a free extended warranty program to at least a subset of its cardholders. Unfortunately, that doesn’t mean you can count on your card without a second thought, as the difference between the best and worst credit card warranty plans is substantial, according to Card Hub’s 2012 Credit Card Extended Warranty Study.

Generally speaking, American Express offers the best extended warranty program, as it received a score of 90 percent in Card Hub’s study. Discover (80 percent), MasterCard (71 percent) and Visa (67 percent) followed in that order. All four networks provide up to one year of additional coverage on top of certain existing warranties and will cover amounts up to $10,000. The biggest areas of differentiation were found in the likelihood that one’s card will be covered, the types of purchases that qualify for the benefit, the length of the original manufacturer’s warranty, and policies regarding coverage for refurbished items.

Who’s covered: All Discover and American Express cardholders are covered under their network’s extended warranty program, while MasterCard provides it to people with Gold, Platinum, World and World Elite cards. Visa only offers coverage to those with Signature-branded cards.

Types of purchases covered: While electronics, jewelry and many other items of personal property that you’d assume to be covered are, in fact, covered, motorized vehicles (e.g. ATVs, boats and cars) aren’t covered under any of the networks’ plans. Perhaps more disconcerting is that MasterCard and Discover policies do not cover damage occurring as a result of “normal wear and tear,” which could give them a blanket excuse to reject claims. MasterCard further excludes physical damage to an item and mechanical failure resulting from a lack of maintenance, adding to the confusion.

Length of existing warranty: If a given item has an original manufacturer’s warranty for longer than 12 months, MasterCard won’t extend coverage. This is likely to significantly limit the number of purchases for which being a MasterCard cardholder will provide much benefit. The other networks don’t have limits that are as constricting, but they have limits nonetheless. Visa and Discover only cover items with existing warranties of three years or less, and American Express has the most generous policy, only restricting coverage to those with warranties of five years or less.

Refurbished items: Only American Express will cover refurbished items, though they must still come with a manufacturer’s warranty. This is particularly important in light of the large secondary market for refurbished electronics on sites like eBay and through major retailers like Apple.

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While the above exclusions might have overwhelmed you, the good news is that you don’t have to sign up for extended warranty protection or register specific items in order to benefit (though Visa recommends product registration). I know, usually when you hear about such benefits, there are a ton of administrative hoops that you need to jump through that drive you so crazy you’d rather spend money just to avoid dealing with them. In this case, however, all you have to do to benefit is keep copies of your purchase receipt, your credit card statement showing the relevant charge, and your original manufacturer’s warranty so that you can file a claim when needed.

At the end of the day, two things are clear: 1) Credit card extended warranty programs mean that you don’t have to give retailers more of your money than is truly necessary; and 2) Just because credit cards offer extended warranty protection, don’t assume you’re covered. So before you say “yea” or “nay” when a retailer asks you if you’d like to purchase protection, think about what’s inside your wallet and whether it already has your back.

Odysseas Papadimitriou is the CEO of Card Hub, a website that helps consumers compare credit cards and sell unwanted gift cards.