You might want to gas up on Sunday.

The state Public Utilities Commission said yesterday that the wholesale gas cap will be increased by a little more than 7 cents a gallon on Monday.

Winter weather on the Mainland and higher demand have led to higher oil and gas prices nationwide. Hawai'i, the only state in the nation to control gas prices, sets a limit on wholesale prices based on an average of Mainland rates and adjusts the limit each Monday.

The cap for O'ahu will rise to $1.82 for a gallon of regular Monday, up from $1.75 this week, the agency said. Next week's cap price will be the highest in four weeks. Prices at the pump likely will be about 74 to 82 cents higher after taxes and dealer markup are added.

The cap is calculated with market data in three Mainland markets where wholesale prices increased in the past week because of speculation about lower oil inventories as cold weather swept over the northeast.

Hawai'i has the nation's highest gasoline and diesel prices. The statewide average of $2.635 for a gallon of regular on Tuesday night compared with the U.S. average of $2.138, according to the American Automobile Association.

The wholesale cap is computed using wholesale prices from New York, the Gulf Coast and Los Angeles and doesn't regulate prices at the pump. Retail rates generally have moved in the same direction as changes in the cap, however.

The state Public Utilities Commission also is monitoring how much wholesalers and distributors are charging through filings the companies are required to make. PUC spokeswoman Lisa Kikuta said the agency is reviewing the reports and have asked for some follow-up data.

The PUC set the cap for Kaua'i at $1.9624 and Maui excluding Hana at $1.9604.

Moloka'i's cap will be $2.0684 beginning Monday, while Lana'i's wholesale price ceiling will rise to $2.1594.

On the Big Island, the cap for Hilo was set at $1.9694. Kona's cap was increased to $1.9884.