How to calculate a House’s Electrical Load


How to calculate a House’s Electrical Load


Calculating your house’s electrical load can help you learn where you are spending money on electricity and give you options on lowering your utility bill. There is not an exact science to calculating the electrical load of a home, but here are a few steps that will help you get a good overview of how you use electricity in your house.

Step One

Know what you want to calculate. This can seem difficult but it's really not too hard once you learn the terms. Most electrical appliances are rated with watts, while some use amps. To convert amps to watts, multiply the number of amps by 120. You do this because U.S. home electric outlets use 120 volts, and volts multiplied by amps equal watts. The number you want to find is how many kilowatt hours (kWh) you are using.

Step Two

Create a log of what electrical appliances you use and how long you use them at a time. Keep in mind things that you do not actively control like heating or cooling units, water heaters and refrigerators. Make a list over several days of all the appliances you used, to find a good average on each.

Step Three

Check the labels on your electrical appliances. This is a start to calculate your electrical load and is a good way to get an idea of how much power each appliance uses. One thing to remember is that the number on the label is the maximum watts that appliance will use in an hour, so a refrigerator for instance will only use a small amount of power unless the compressor is running at which time it will use closer to the maximum power.

Step Four

Estimate the amount of watts you use per appliance a day. If you need help for appliances like heating and cooling units, water heaters or other passive appliances, you can find many estimations on the Internet with a simple web search.

Step Five

Calculate the kWh use for each appliance. The formula for kWh is watts multiplied by hours used and then divided by 1000. For instance, a 100-watt light bulb used for 10 hours would use one kWh.

Step Six

Add all of the kWh results from your appliances to get an idea of your electrical load that you use every day.

Step Seven

Use a watt-meter to get a better idea of how much electricity individual appliances use. A watt-meter will connect between your appliance's plug and the wall outlet and it will tell you how much electricity the appliance uses over time. This is a good way to get a more exact calculation.


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