At Kiraku, a busy izakaya in Berkeley, dinner might come with a surcharge that you won’t see at many Bay Area restaurants. Notices can be found at the entrance, by the cash register, on the menu and on a little card that comes at the end of the meal.

The culprit for a higher bill? Using a credit card.

Kiraku is one of the first restaurants in the Bay Area to charge diners an extra fee for paying with plastic. The move hasn’t kept diners from lining up nightly for corn tempura and grilled beef tongue, but other restaurant owners are nervous about following Kiraku’s lead.

Understandably so.

“Some people get really angry,” said Kiraku co-owner Sanae Saito. “Some post one-star reviews on Yelp complaining.”

As the costs of running a restaurant in the Bay Area continue to rise and profit margins remain low, owners are eyeing credit card surcharges as one potential way to save a lot of money — as much as $100,000 per year, depending on the size of the restaurant.

When a diner pays with a credit card, the restaurant ends up paying a processing fee that is usually somewhere between 2% and 4%, depending on the card. American Express is known for the highest fees, as are those with bonus rewards like airline miles.

“We’re tired of paying for vacations,” said Rich Azzolino, owner of Sotto Mare in North Beach.

Adding a credit card surcharge to checks wasn’t always possible. In 1985, California passed a law prohibiting businesses from charging customers more for paying by card instead of cash. Several businesses challenged that law on the grounds of free speech, arguing they weren’t able to effectively communicate their pricing. In January 2018, a federal appeals court ruled in favor of the businesses, setting a legal precedent for restaurants statewide.

Oakland’s Italian Colors was one of the legal challengers, yet the restaurant still isn’t charging customers to use cards. Chef-owner Alan Carlson said he gets phone calls constantly from fellow restaurateurs asking about the law and why he hasn’t acted on it.

“I don’t like to confuse my guests,” he said. “It’s a hard one. We’re in a quandary.”

Carlson said if more restaurants start enacting surcharges, he’ll likely follow suit — he estimates paying more than $70,000 per year in credit card fees. That could pay for a manager’s salary.

Other restaurant owners, including Azzolino, echoed Carlson. No one wants to be a pioneer, even if they think surcharges will become the norm in the future.

“I don’t know if I’m willing to take that bet right now and cause a lot of people to get mad at me for yet another charge on their bill,” said Joe Kohn of Cow Hollow steakhouse Izzy’s San Francisco. “Tax, health care and now another charge for using your card? It might be too much for anyone to handle right now.”

Restaurateurs also aren’t sure how they would best communicate such a surcharge. Kohn went as far as testing his point-of-sale system to see if it could add the new charge, but the charge accidentally got activated during service one night. A couple of diners complained, and Kohn quickly abandoned the effort.

“It looks like you could be tricking the customer,” he said. “You drop the bill and it’s $100. Then they give the credit card and suddenly it’s $104. It feels like a bait and switch.”

Saito of Kiraku and her husband, Daiki, made every effort to ensure customers know about the potential surcharge — roughly 4.5%, though it depends on the check total — by putting notices throughout the restaurant. Since they enacted the system in November 2018, many more people pay with cash.

A few other Bay Area restaurants have quietly made changes following the 2018 court ruling. In the Outer Richmond, New Oyaji Restaurant created a similar system to Kiraku, passing along the credit card fees to diners. Berkeley’s Agrodolce Osteria takes a different approach by offering a 5% discount to diners paying cash.

While some restaurateurs debate surcharges and discounts, others would rather take the opposite approach and go completely cashless. Those business owners most often cite the risk of getting robbed when there’s a lot of cash on hand. Plus, there are labor costs associated with handling cash — analyst firm IHL Group estimates they can add up to 4.7% to 15% of sales. Yet San Francisco banned cashless businesses this year with the view that the practice discriminates against people who don’t have bank accounts.

Lex Gopnik-Lewinski opened Augie’s Montreal Smoke Meat in Berkeley last year as a cashless restaurant but grew to accept the idea that allowing cash is more inclusive. Still, he actively steers diners toward paying with cards when they have them. He said the processing fees are worth having a more efficient operation and avoiding constant trips to the bank.

“We’re going toward a cashless world,” he said. “It’s just the cost of doing business nowadays — you’ve got to evolve and stay with the times or go extinct.”

The Saitos worried about being the first in the neighborhood to charge for card use. Relief took over when they found their regular customers, who make up the bulk of their business, understood the decision and continued coming back.

Daiki Saito said they’re saving about $40,000 per year. If they didn’t add the credit card surcharge, they would have had to raise prices across the board, and this system felt more fair.

“Minimum wage gets higher and higher. Japanese fish costs more. Rent has doubled. That’s why we had to start thinking about saving money,” Daiki said. “I think 95% of people don’t care, 5% are yelling. But I don’t care about the yelling people, because they don’t know how tough it is to run a restaurant.”

Janelle Bitker is a San Francisco Chronicle staff writer. Email: janelle.bitker@sfchronicle.com Twitter: @janellebitker