It can be so incredibly tempting: You’re at the cashier (or about to check out online) with a substantial purchase and you’re presented with the offer to save money now if you just apply for a store-branded credit card. But if you don’t pay off that balance right away, you could be looking at interest rates nearly double the national average.

The folks at CreditCards.com have put together their annual survey of retailers’ credit cards, and found that most store-branded cards are probably not a good deal for anyone who needs to carry a balance.

According to the survey, which looked at 64 cards issued by the nation’s top retailers, the average interest rate on a store-branded card is 23.43%, more than eight percentage points higher than the national average for all credit cards.

Put in terms of actual dollars, a $1,000 balance on a 23.43% card will take 72 months to pay off and result in $833 in interest payments if you pay the minimum allowable amount. Compare that to 54 payments and $370 in interest for someone who pays the minimum on a 15% card.

Retail credit cards come primarily in two formats — store-only cards that can’t be used outside of the retailer that issues the line of credit; and co-branded cards that carry a retailer’s name but can be used to make purchases through a credit card network like Visa, MasterCard, or American Express.

In general, the store-only cards carried higher interest rates than the co-branded cards, even at the same retailer.

For example, the Amazon “store card” that can only be used on Amazon.com charges an APR of 25.99%, but Amazon’s co-branded Rewards Visa card offers interest rates ranging from 14.74% to 22.24%.

But co-branded cards aren’t always less expensive. Both of Best Buy’s credit card offerings — its store-only line of credit and its co-branded Visa card — come with an APR of 25.24%.

The card with the highest APR comes from jewelry chain Zales. Its store-only card leads the pack with a whopping 28.99% APR.

Interestingly, Zales is part of the Signet Jewelers family, and other Signet companies have less-unfriendly credit offerings. Both Jared and Kay have store-only cards with interest rates that range from 17% to 24.99%. That’s still much higher than the national average, but lower than Zales.

One store-only card that deviates from charging a high interest rate is the Army Air Force Exchange’s Military Star card. It can only be used at exchanges, but the interest rate is a lower-than-average 10.24%.

There were other retail cards where cardholders could possibly end up with APRs below 16%, but only the Military Star card and Costco’s AmEx (which is soon to disappear) had fixed rates. The others all offered lines of credit with a wide range of APRs that all top out higher than 20%.

For instance, Nordstrom has two cards with interest rates as low as 10.90%, but an applicant could end up with an interest rate as high as 22.90%.

Similarly, both Apple and Ace Hardware have store-branded cards that start at 13.99%, but the Ace card could end up as high as 22.99% while Apple’s reaches a maximum of 26.99%.

“If you regularly carry a balance, retail credit cards just aren’t for you,” said Matt Schulz, CreditCards.com’s senior industry analyst. “Even with potential rewards and discounts, the math just doesn’t work in your favor when interest rates are that high.”

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.