This is easily calculated provided that you have the local price of the fuel to be used. 1 cubic foot of natural gas will produce *1000BTU per hour, 1 litre of propane will produce *29,059 BTU per hour and 1 US Gallon will produce *110,000 BTU per hour. (*values may vary slightly, depending on location) The BTU of the fireplace is divided by the BTU value of the fuel to determine the amount of fuel consumed per hour. Example: A natural gas fireplace that has an input of 30,000 BTU per hour consumes 30,000 / 1000 = 30 cubic feet/hour. If the price of natural gas is .35 cents ($0.0035) per cubic foot then 30 cubic feet x .35 = 10.5 cents ($0.105). Therefore the cost of operating one of our 30,000 BTU Natural Gas Fireplaces such as the new GDS28 Gas Stove for one hour is 10.5 cents.