About 250 million extended warranties for electronic devices are purchased each year, including 11 million for PCs and laptops, according to the Service Contract Industry Council.

And during this year’s holiday shopping blitz, you’ll mostly likely be asked to buy them many times at the checkout.

Resist the sales pitch, Consumer Reports advises.

Extended warranties are widely available for popular high-tech items, like LCD TVs, laptops, e-readers and tablets, and are sold as investment protection for these pricey gadgets.

But at 10 to 20 percent of a product’s cost, these supplemental service plans aren’t worth it, Consumer Reports warned in this month’s issue. The magazine’s survey found that extended warranties came up short in numerous ways and are overall bad investments.

For one, products often last much longer than the warranty period, free of defects and breakdowns. Secondly, warranties aren’t cheap, typically boosting the price of an item by a third. Third, warranties don’t live up to expectations, with consumers complaining about slow or no response to claims, no record of the warranty from the provider, claims being denied due to no nearby repair shop or damage determined to be the fault of owner. The survey also found that warranty periods sometime coincided with the manufacturer’s warranties for some purchasers.

Besides, some credit cards provide coverage to cardholders by extending the manufacturer’s warranty, with some limitation, sometime up to a year after purchase.

“Our reader surveys show that many consumer products are reliable, making a service contract unnecessary,” the magazine stated. “If products don’t break while the manufacturer’s warranty is in effect, they probably won’t during the service-plan period, particularly if you buy brands that we’ve judged to be especially reliable.”

In addition to increasing the total price of a item, repair costs under a warranty aren’t substantially less than without one, the magazine survey revealed.

“You can self-insure by putting the cost of contracts into a dedicated bank account for repairs and replacements,” the magazine article recommended. “That way, even if you have to pay to repair or replace an item, you’ll still probably be ahead overall.”

The magazine also found that companies are striving for customer satisfaction and may extend manufacturer’s warranties when damage and defects are reasonable, offering repairs and replacement upgrades through goodwill programs.

In addition, the survey showed that out-of-pocket repairs were more likely to be addressed promptly and more efficiently than going through an extended-warranty plan.

But the Service Contract Industry Council, a national advocacy organization for extended warranties disagrees with Consumer Reports. In a slow economy, these service contracts can guard against unexpected repair costs, the trade group said.

For example, costs to repair cracked screens for both eReaders and tablets can range from $160 to 350. To replace or upgrade a battery can run up to $150; fixing lines in a screen, between $160 and $350.

A laptop may cost $650 and its warranty between $65 and $130. Without an extended warranty, replacing a faulty motherboard can cost $450, and repairing a hard drive could come up to $350, the council found. In the case of a $1,500 LCD TV, a warranty on average runs from $150 to $300, but fixing components like the panel can cost $1,200; a control box, $560; and power supply, $265.00.

“While some maintain consumers should put aside cash for repairs and replacement of essential electronic products or appliances, it is not possible or practical in today’s economy,” said Timothy J. Meenan, executive director of the council.

Furthermore, with manufacturers’ increasing tendency to redesign and build complex products with cheaper materials, a plan could come in handy, according the council. The group only warns against purchasing service plans when there’s pressure from salespeople to purchase; if there isn’t a contract to review when a items are bought; and if the warranty’s price is more than 10 to 20 percent of the total price of the item.

But Consumer Reports said these service plans are most beneficial for retailers. In fact, salespeople can be aggressive about adding a plan because they are their cash cows for stores. Retailers keep 50 percent or more of what they charge for the plans. For retailers extended warranties can be more lucrative than actually selling products.