My furnace has an 80,000 BTU burner (equivalent to 23,000 watts), and a 1/2 horsepower blower, which would use around 600W. So the blower uses less than 3% of

My furnace has an 80,000 BTU burner (equivalent to 23,000 watts), and a 1/2 horsepower blower, which would use around 600W. So the blower uses less than 3% of the energy used by the burner. Some of the waste heat from the blower motor probably helps heat the home, so in reality it's probably less than that. While startup current is significant (for a very short time), starting the fan up in the morning and again in the evening after work doesn't add that much to the total power drain, or even cycling it on/off a few times an hour to maintain temperature. Starting wattage on that motor is around 1800W, but only lasts for a few seconds.