Credit card debt is rising, and shopping for a card with a lower interest rate can help you save money. But the challenge is finding one.

Smaller banks and credit unions typically charge significantly lower interest rates on credit cards than the largest banks do — even among customers with top-notch credit, the Consumer Financial Protection Bureau reported last week.

But online card comparison tools tend to emphasize cards from larger banks that pay fees to the sites when shoppers apply for cards, said Julie Margetta Morgan, the bureau’s associate director for research, monitoring and regulations. “It’s pretty hard to shop for a good deal on a credit card right now.”

For cardholders with “good” credit — a credit score of 620 to 719 — the typical interest rate charged by big banks was about 28 percent, compared with about 18 percent at small banks, the report found.

For those with poor credit — reflected by a score of 619 or lower — large banks charged a median rate of more than 28 percent, compared with about 21 percent at small banks. (Basic credit scores range from 300 to 850.)

The variation in the rates charged by big banks and smaller ones can mean a difference, on average, of $400 to $500 a year in interest for cardholders with an average balance of $5,000, the bureau found.

“I was surprised by the gap” between the rates, said John Pelletier, director of the Center for Financial Literacy at Champlain College in Burlington, Vt.

The difference is more than academic, since Americans owe more than $1 trillion in credit card debt and delinquencies are rising.

The consumer bureau, in its report, said a “lack of competition likely contributes” to higher card interest rates at the largest card companies. (The top 10 issuers represented 83 percent of credit card loans in 2022, although that was down from 87 percent in 2016, the bureau reported in October.) A deal to combine two big card issuers, Capital One and Discover, was announced this week and is likely to draw regulator scrutiny because of concern that it would give larger financial institutions even more power to set higher rates.

In response to the bureau’s report, the Consumer Bankers Association, a trade group representing mostly large banks, defended the credit card market as “highly competitive” and criticized the bureau for making “troubling, unfounded” statements.

“A thriving marketplace means that consumers can choose products that may have different prices and offer features, perks or other value that’s specific to them,” the association said in a statement.

The bureau based its report on 643 credit cards offered by 84 banks and 72 credit unions during the first half of 2023. Most cards were available nationally, while the rest were offered regionally or in a single state. The report includes annual percentage rates, or A.P.R.s, on general purpose cards offered by the 25 largest card issuers (based on outstanding credit card assets), plus a sample from small and medium-size banks across the country.

The bureau collects data on credit cards in a survey twice a year; last spring the survey began asking for more details, like how credit scores affect rates.

Federally chartered credit unions have a statutory cap of 18 percent on the interest rates they can charge, the bureau noted. But smaller banks also had lower rates overall.

Fifteen card issuers, including nine of the biggest, reported offering at least one card with a maximum rate above 30 percent. Those banks included familiar names like Ally, Capital One and Citibank. (Many such cards were “co-branded,” the bureau said, meaning they also bore the name of partners like stores or airlines.)

A card’s interest rate is of less importance to people who pay their balance in full each month, since they’re not paying interest. Those consumers may be more interested in using credit cards for “cash back” rewards or for points that translate into savings on purchases like frequent flier miles or hotel stays.

But if you’re a “revolver” who regularly carries a balance, a double-digit interest rate will probably wipe out any benefit from cash back or points. “You shouldn’t be choosing a card based on points” if you typically carry a balance, said Adam Rust, director of financial services at the Consumer Federation of America.

Many people, though, undervalue the impact of interest rates on their credit card debt. “The immediate gratification of purchasing, coupled with the deferred pain of payment, can overshadow the long-term financial costs represented by the A.P.R.,” Sachin Banker, an assistant professor of marketing at the University of Utah’s business school, said in an email.

People might pay more attention to card rates if they understood the compounding of interest over time, Mr. Pelletier said. He calculates that someone with good credit who carried a card balance of $5,000 would save $42 a month by using a card with the typical small bank rate instead of the big bank rate.

Even if you regularly pay off your card balance, it’s a good idea to have a lower-rate card since an unexpected expense — a medical bill, say — may require you to carry a balance temporarily.

The consumer bureau has said it is considering creating a public search tool that would include a variety of cards from big banks and small. “We are actively looking at that right now,” Ms. Morgan said.

The bureau already makes available an online spreadsheet showing the terms on cards included in its survey.

The Independent Community Bankers of America, a trade group, offers a search tool for local banks at www.banklocally.org. You can then check the websites for card rates or call for information.

The National Credit Union Administration offers a search tool for credit unions. Many limit membership to certain groups, but some are more flexible.

Here are some questions and answers about credit cards:

Do annual credit card fees vary by the size of the issuing bank?

Cards issued by large banks were three times as likely to charge an annual fee as those from smaller banks, the consumer bureau’s report found. Plus, the average fee at big banks was larger — $157, compared with $94 at smaller ones.

Why are credit card rates so high?

Credit cards offer “unsecured” loans — meaning the debt isn’t secured by collateral, as it is with a mortgage or car loan. If you don’t pay your bill, the bank can’t seize property to cover its losses, so it charges higher rates to compensate for its risk. More recently, card rates generally rose as the Federal Reserve raised its benchmark rate to cool inflation.

But in a separate analysis published on its website on Thursday, the consumer bureau said card issuers had raised interest rates significantly above prime lending rates, costing consumers more interest.

How can I be sure to get the best credit card rate?

An important factor in qualifying for a good rate is your credit score, which is based on information in your credit report. Before applying for a new card, check your report for accuracy. (A recent analysis from Consumer Reports found that complaints to the federal government about inaccurate credit reports had more than doubled since 2021.) You can check your report at the three big credit bureaus as often as weekly at no charge, at www.annualcreditreport.com.