Survey: US Gas Prices Drop 6 Cents a Gallon The average price of regular gasoline in the U.S. has dropped 6 cents a gallon during the past two weeks. Industry analyst Trilby Lundberg said Sunday that a gallon of regular now costs $3.52 on average. Of the cities surveyed in the Lower 48 states, San Francisco has the highest price at $4.01 a gallon. Charleston, S.C., has the lowest at $3.14 a gallon. The average price in California is $3.97 a gallon, up 16 cents from two weeks ago. The decrease was recorded by the Lundberg Survey.