It is fairly easy to compare and convert the annual energy costs of oil, gas and electric furnaces and heat pumps. Fuel burning appliance are rated by Btu’s, operating efficiency and the actual fuel costs.

Electrically heated appliances are rated by btu’s and kilowatts and the actual kilowatt costs. The standard for rating electrically powered heat pumps is the Coefficient of Performance (COP). Having a COP of 1.0 means that an appliance consumes one kilowatt of electricity to produce one kilowatt of energy. A COP of 2.0 means one kilowatt in and two kilowatts out, etc., etc. We know that one kilowatt of electricity is equal to 3413 btuh’s of energy and that gives us a basis of comparison.

We also know that heating oil yields about 140,000 btu’s per gallon and that natural gas is measured using 100,000 btu’s per therm. We know that oil-burning equipment is about 80% efficient and we harvest 112,000 btuh’s of usable heat per gallon. For this comparison we will assume that the gas furnace is 90% efficient, or supplies 90,000 btu’s per therm of usable heat.

If we used an average sized home in Seattle with an annual heating load of 60,000,000 btu’s as our base, we can breakdown that down into the following:

60,000,000/112,000 btu’s per gallon of oil = 535 gallons of oil at an average cost of $2.50 per gallon equals an annual heating cost of $1,337.50.

60,000,000/90,000 btu’s per therm of gas = 667 therms of gas at an average cost of $1.35 per therm equal an annual heating cost of $900.45.

60,000,000/3413 btu’s per kilowatt = 17,580 kilowatts of electricity at an average cost of .10 per kilowatt equals an annual heating cost of $1,758.00.

Converting the electric heating cost into a heat pump heating costs brings the COP into account. Assuming that the heat pump has an average COP of 2.5 (very conservative) we would yield 8,533 btuh’s per kilowatt or:

60,000,000/8533 btuh’s per kilowatt = 7,031 kilowatts of electricity at an annual average cost of .10 per kilowatt equals an annual heating cost of $703.00.

We now can say that a heat pump with an average operating COP of 2.5 can save 22% versus the cost of operating a 90% efficient gas furnace and provide the benefit of air conditioning during the warmer months. We need to note that heat pumps are much more efficient above 38 degrees and less efficient below 35 degrees. That is why we used an average COP of 2.5.

When you consider that high efficiency heat pumps can also get a $350.00 rebate from PSE and can qualify for a $1500.00 Federal tax credit, heat pumps are absolutely a great option to consider when upgrading your heating system.

Seattle City Light has a nice chart that shows similar savings at the following link; http://www.seattle.gov/light/conserve/resident/homeheating/cv5_fcc.asp

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