The average house has a variety of electronic devices and electric appliances, all plugged into the walls. Some appliances use more electricity than others do, depending on the size and wattage of the unit. Whether you’re trying to conserve energy or you’re just interested in your electricity expenses, it can be an eyeopening exercise to do some simple calculations for your home energy usage.
The U.S. Department of Energy has an Energy Savers website with a guide for helping the consumer estimate the energy use of appliances and home electronics. If you can perform basic mathematical equations, you’ll be able to get an idea of where your electricity dollars are going.
Once you measure your home appliance energy usage, you may be able to figure out ways to cut your electric bill, too.

1.Check the Wattage
Once you measure your home appliance energy usage, you may be able to figure out ways to cut your electric bill, too.
Find the nameplate of the appliance – usually on the back or bottom of the unit. You should see a listing of the wattage – the maximum power used by the appliance. You may also see the letters “UL,” which tells you that the appliance has had testing and it complies with safety standards.
If a unit doesn’t provide the wattage, you can figure it out yourself by using the current it draws (the amperes) and the voltage it uses (probably 120 volts). Multiply the amperes by the voltage to get the wattage.
Don’t forget about phantom load for many appliances that remain plugged in but not turned on. This means that these units draw a small amount of electricity even when they aren’t on.

2.Ammeter
An electrician’s ammeter can also measure amperes in an appliance. Clamp the ammeter to one of the wires on the appliance while the appliance is running. Wait for a few seconds to avoid the initial surge of electricity. Then note the numerical display on the ammeter to see the amperes running through the appliance while it is operating.

3.Calculate Energy Consumption
To estimate how much energy an appliance uses, multiply the wattage by the number of hours you use the appliance in one day. Divide this answer by 1,000 to get the daily kilowatthour consumption. Multiply this answer by the number of days you use the appliance in one year to get the annual kilowatthours. Multiply this answer by the local utility rate for kilowatthours. The answer is the annual cost to run your appliance. Divide the answer by the number of days you use the appliance to calculate the daily expense.
For example, if a microwave has a wattage of 1,100 and you use it for about two hours each day, multiply 1,100 by 2 to equal 2,200. Divide 2,200 by 1,000 to get 2.2 daily kilowatthours. If you use the microwave every day of the year, multiply 2.2 by 365 to equal 803 annual kilowatthours. If the rate for electricity per kilowatthour is 12.5 cents, multiply 803 by .125 to equal $100.37 per year to operate the microwave. If you want to calculate the daily expense, divide $100.37 by 365 to equal .27 – it costs about $.27 a day to operate your microwave.

4.Wattage of Some Appliances
A ceiling fan may have up to 175 watts. A vacuum cleaner may have up to 1,440 watts. A dishwasher may have up to 2,400 watts when you use a power dry setting. Once you have a greater awareness of the electricity use of your appliances, you can take steps to reduce your electricity consumption. In some cases, you may opt to replace an older unit with a newer one that has a more energy efficient design.