(See chart 2 .) The price paid by Washington area consumers for utility (piped) gas, commonly referred to as natural gas, was $1.001 per therm in August 2015, 7.4 percent above the national average of $0.932 per therm.rices for a gallon of gasoline in Washington have differed from the U.S. average by 5 or less percent in August over the past five years. (See chart 1 and table 1 .). The Consumer Price Index for September 2015 is scheduled to be released on Thursday, October 15, 2015, at 8:30 a.m. (ET).