ENERGY Efficiency

Home heating: Calculating the benefits of electricity vs. propane

By Anne Prince

energy use in a typical U.S. home, making it the largest energy expense for most households. While few people enjoy spending money on home heating fuels, consumers are willing to pay for comfort in the form of heat. In these colder months when the

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temperatures dip and the need to heat your home rises, it makes sense when trying to determine the most economical heating method to evaluate the cost per unit of heat. Tis is referred to as a British thermal unit (Btu).

EVALUATING COST PER UNIT OF HEAT FOR PROPANE AND ELECTRICITY Te Btu content per gallon of

propane is 91,500 Btu. Te Btu content for electricity is 3,413 Btu per kilowatt-hour (kWh). It takes 26.8 kWh to equal the Btu content of one gallon of propane. Using the U.S. Energy Information

Administration’s table on residential propane and electricity rates for November 2014, \$2.40 per gallon, excluding taxes, and 13.01 cents per kWh, we arrive at the following calculation:

26.8 kWh x 13.01¢ = \$3.49 If we used only Btu content to

determine the best energy source for home heating, it would appear that propane is less costly than electricity

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ccording to the U.S. Department of Energy, heating and cooling account for nearly half of the

if the price for propane is below \$3.49 per gallon.

COMPARING USABLE HEAT COSTS While we may have determined

the cost of the actual heat content, what matters even more is the cost of the usable heat (warmth). A low- efficiency propane furnace may have an efficiency rating of 80 percent, and a high-efficiency propane furnace may have an efficiency rating of 95 percent. Let’s assume we have a 90 percent efficient propane furnace. Tat means 10 percent of the Btus are not converted to usable heat (warmth). Here is the math:

91,500 Btu- 10% Btu loss = 82,350 Btu

So now it

only requires 24 kWh to equal the delivered Btu content of propane.

24 kWh x 13.01¢ = \$3.12

ELECTRIC HEAT IS 100 PERCENT EFFICIENT What may surprise most

consumers is that the least efficient electric heating system delivers 100 percent efficient heat. Yes, electric resistance heat (i.e., space heaters, baseboard heating) is 100 percent energy efficient. Every single Btu in a kilowatt-hour is delivered as usable heat. So if you are paying more than \$3.12 per gallon of propane for a 90 percent efficient propane furnace, it would be cheaper to use electric resistance heat.

OKLAHOMA ELECTRIC CO-OP NEWS • FEBRUARY 2015

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