Using practical examples of the appliances and objects found in every home, your students perform basic calculations to reveal how much electricity they use.
You can either collect and assess the “Measuring electricity use” worksheet or have the class work through the answers together.
Worksheet Answer Key:
|Energy||The ability to do work||energy = power x time|
|Watt||A unit of electrical power. The rate at which an appliance or device uses power||1 watt = 1 joule/second|
|Power||The rate at which energy is transformed or the rate at which work is done||power = energy/time|
|Kilowatt||A measure of the amount of energy used over time that indicates how fast you are using energy||1 kW = 1,000 watts|
|Kilowatt-hour||The amount of energy used when an appliance or device consumes 1 kilowatt of power for 1 hour||100-watt light bulb x 10 hours of use = 1 kWh|
|Appliances and products||Power (watts)||Average use (hours per day)||Annual energy usage (kWh)||Annual cost ($ per year)|
|Vacuum cleaner||1,100||0.1||40.2 kWh||$3.33|
|Hair dryer||1,200||0.25||109.5 kWh||$9.08|
|Clothes dryer||4,000||2.0||2,920 kWh||$242.07|
|Incandescent light bulb||60||3.0||65.7 kWh||$5.45|
|Compact fluorescent light bulb||14||3.0||15.33 kWh||$1.27|
|LED light bulb||8||3.0||8.76 kWh||$0.73|
|Flat-screen TV||200||5.0||365 kWh||$30.26|
How is the use of electricity measured?
The watt (W) is a unit of electrical power, which is the rate at which an appliance or device uses energy.
What is a kilowatt?
A kilowatt (kW) is equal to 1,000 watts.
What is energy?
Energy is the ability to do work. Electrical energy use is measured in kilowatt-hours (kWh). Another unit of energy is the joule. For example, in homes we measure the use of natural gas energy in gigajoules.
What is a gigajoule?
A gigajoule (GJ) is equal to 1,000,000,000 (one billion) joules.
How do you convert gigajoules to kWh?
1 GJ equals 277.8 kWh.