The cost of a gallon of regular gas in Kentucky is a nickel lower than a week ago. Heading into the weekend, Triple-A says the average price per gallon in the state is two-dollars-and-78-cents today, while the national average is two-90. Drivers in Louisville are paying the most in the Commonwealth at two-89 a gallon. The lowest prices are posted in the Elizabethtown-Fort Knox area at two-64.