An Estimate of Energy Usage During Run Time of HVAC Equipment

Watts

• Electric appliances are rated by the number of watts used to power them while operating. For example, a 100-watt light bulb requires 100 watts to operate. A 800-watt kitchen top microwave requires 800 watts to operate. A small clock may consume only 10 watts of power. The difference is that using electricity to generate either light or heat takes a much larger amount of power. Electric furnaces generate heat by design, and air conditioners generate it by compressing refrigerant and sending the heated gas to the outside.

Gas Furnace

• A gas furnace is more difficult to quantify in the amount of gas it uses. Older models use significantly more than models made after the federal government started promoting the Energy Star benefits to manufacturers and consumers in the early 2000s. The size of the furnace and the efficiency with which it is working at any any given moment determine how much gas it consumes to heat the home. Both induced-draft and condensing furnaces are more efficient than conventional furnaces, and a two-stage burner is more efficient than a one-stage.

  A gas furnace uses about 750 watts of electric power when it is running, to power the blower fans.

Electric Furnace

• An electric furnace can consume as much as 26,500 watts heating a 2,000-square-foot home in a cold climate and 8,000 watts in a 1,000-square-foot home in a warm climate, according to the Michael Bluejay website. Comparing that with a mere 350 watts to run a desktop computer and monitor, it is easy to see how the costs of heating can make an electric bill skyrocket.

Air Conditioning

• As with a furnace, an air conditioner's power usage varies with the size of the home and the HVAC unit and its efficiency. Typical examples of the watts consumed provided by the Generatorsales website are a window air conditioner at 4800 watts, a 10k BTU (British thermal unit) central air unit at 6,000 watts, 24k BTU at 15,000 watts and a 40k BTU unit at 24,000 watts. Keeping both a furnace and an air conditioner maintained according to the manual helps reduce their energy consumption by boosting their efficiency.