According to the Department of Energy, large office buildings (those with more than 100,000 square feet) use an average of 20 kilowatt-hours (kWh) of electricity per square foot and 24 cubic feet of natural gas per square foot annually. The average commercial electricity rate in the US 11.33 cents per kWh (EIA November 2021). That makes the average monthly electricity bill for a 100,000 square foot office building around $19,000.