Q: I have an electric furnace that keeps the house warm, but I can’t keep up with the bills. I was thinking of buying a space heater, but I don’t know if that will save me any money if I have to keep it on all the time. Do you have any suggestions or recommendation?
A: The utility company charges users per kilowatt hour (kW/h), which is 1,000 watts of power usage per hour. All electrical appliances, tools, laundry equipment and heating/cooling equipment use watts of power when in use.
If you have a 100-watt light bulb that stays on for eight hours a day, it will use 800 watt hours of electricity (100 X 8 = 800). If you use the bulb every day for a month, it will use (30 x 800) or 24,000 watts and you would be billed for 24 kilowatt hours per month or 24 kWh/m.
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I used the light bulb as an example because the furnace, like the bulb, is not on 24 hours a day every day for a month. The furnace will cycle off and on to keep the entire home warm.
Your energy bill depends on the weather, how much insulation the home has, how big the home is and the thermostat’s temperature setting.
One of the smallest electric furnaces for a residence is a 10kW model, one that uses 10,000 watts of energy when turned on.
Assuming that the furnace would cycle off and on for a total of five hours a day, the furnace would use (5 hours x 10 kW) or 50 kW/h a day. Extend that to a 30-day month, (30 days x 50 kW/h) equals 1,500 kW/h/m.
Using an electrical rate of 16 cents per kW/h, the furnace would cost $240 per month to operate, not including the costs of running the furnace’s 700-watt electric fan.
A typical electric or radiant space heater is rated between 1,000 watts and 1,500 watts.
That’s a huge difference, compared to an electric furnace, even if the space heater is on all day and night.
A 1.5 kW/h space heater used for 24 hours a day for 30 days equals 1,080 kW/h/m. The cost to operate the space heater would be ($0.16 x 1,080 kW/h/m), which equals $172.80. That’s a predicted savings of $67.20 per month, but there are so many variables involved, such as regional weather, how the home is situated with reference to the sun, the number and type of windows you have, air leakage to the home, the color of the roof, etc., that the savings will vary from home to home.
Since each home and each occupant of the home have different needs, it would be wise to find out where you are losing energy by having a professional energy audit performed. The auditor can determine if the use of a space heater only would be practical and if turning the furnace to its lowest setting might cause condensation damage to the rooms you close off and if the plumbing might be affected by the cold.
For more information on energy audits, visit www.energy.gov and search for “energy audits.” Also, contact your local utility to see if it provides assistance or audits that could help you conserve energy.