Iowa drivers are paying $.08 below the national average for a gallon of regular gasoline. Triple A says the cost of gas in iowa is $2.40 a gallon--$2.48 nationwide. The lowest prices in the state can be found in Sioux City at $2.29 a gallon, followed by Cedar Rapids at $2.31. Des Moines drivers continue to pay the most for gas at $2.48 a gallon, the same price as a week ago.