How to Calculate the Energy Usage of a Space Heater
It may be helpful to calculate how much energy your space heater uses. You can compare the energy use of the space heater to that of the central heater in your home to determine if you can save energy by using a space heater. You can also see if you can reduce the energy use of your space heater by modifying your habits (like wearing warmer clothes, for example). Does this Spark an idea?
Instructions
-
-
1
Find the power rating of the space heater in watts. It should be on a label on the side or bottom of the heater.
-
2
Estimate the number of hours per day and the number of days per month that you use the heater. Calculate the total hours of use per month. For example, say you use it on average three hours per day in your home office during weekdays and one hour per day in the bedroom before you go to sleep every night. For a month with 31 days and 22 weekdays, that would be: (3 x 22) + (1 x 31) = 97 hours per month.
-
-
3
Estimate the percentage of time that you use the heater on high, medium or low settings. For example, you may estimate that you use the heater 80 percent of the time on low and 20 percent of the time on high.
-
4
Calculate the average watts for your use of the heater. For a heater that is rated 1,500 watts, it uses on average about 1,440 watts on high setting, 900 watts on medium and 600 watts on low. If it is used 80 percent on low and 20 percent on high, that would be: (0.80 x 600 watts) + (0.20 x 1,440 watts) = 480 + 288 = 768 watts.
-
5
Multiply the average watts times the monthly hours of operation to calculate energy use for the month. If the heater uses on average 768 watts for 97 hours in one month, it would be: 768 watts x 97 hours = 74,496 watt-hours per month.
-
6
Divide by 1,000 to find the kilowatt-hours (kWh) of use: 74,496 watt-hours ÷ 1,000 = 74.5 kWh/month.
-
1
Tips & Warnings
To calculate annual energy usage, figure out the amount used for each month separately, since it is likely to vary a lot depending on the time of year.
You can purchase a small device called a watt-meter. Plug the space heater into the meter and the meter into the wall, and it will calculate the amount of watt-hours used.
