The price of regular gasoline at Honolulu's deepest discounter, Costco Wholesale, rose 18 cents a gallon to $2.76 in the past two days.

That jump comes on the heels of Hawai'i's new gasoline price cap law, which prevents wholesalers from selling gasoline this week for more than $2.76 a gallon, including taxes. Costco's retail price is considered a good barometer for current wholesale gasoline prices because of the company's no-frills, high-volume, low-margin approach to selling gasoline.

Robert Loomis, general manager for Costco's Iwilei location, said the rise in the pump price reflected an increase in the wholesale price of gasoline charged by his suppliers. "Our cost has increased and that's the reason," he said.

The gasoline Costco sells is supplied by Aloha Petroleum.

"The details of agreements Aloha Petroleum has with its resellers are confidential," said Bob Maynard, Aloha Petroleum president. But clearly, wholesale and retail fuel prices have been adversely affected throughout the industry by the devastation along the Gulf Coast. In Hawai'i, the (wholesale) price cap hasn't helped the situation."

That cap is set once a week based on wholesale prices in Los Angeles, the Gulf Coast and New York. Before the cap, Hawai'i prices were generally based on Asian and Alaskan crude oil and gasoline costs. The caps don't require wholesalers to price at the maximum allowed, but economists and oil industry analysts said it is likely they will to offset times when they are forced to lower prices.

Even with Costco's price increase, its regular gasoline was still about 12 cents cheaper than the statewide average of $2.883 as reported by the AAA Fuel Gauge Report. On Wednesday, before the wholesale cap took effect, Costco's price for regular was $2.58 a gallon, or 26 cents below the statewide average of $2.84 reported by AAA.

Costco will still offer members gasoline at a significant discount compared with other nearby stations, Loomis said.

"We will continue to maintain that," he said.

Reach Sean Hao at shao@honoluluadvertiser.com.