What is a Kilowatt Hour?
Your electricity bill measures your consumption in kWh. Yet your appliances - such as your toaster, microwave, or fridge - will indicate a power rating in kW. What is the difference between the two? Our guide will help explain so that you can better understand your electricity consumption.
What is a kilowatt?
A kilowatt is a measure of power. Power is the rate at which energy is converted from one form to another; it measures how quickly energy is being used. This relationship is clearer when power is measured in terms of Joules (a unit of energy) per second. In fact, a watt is another name for Joules/second.
However, a watt (J/s) is a small unit for measuring power, especially when we are talking about consumption at large scales (think about how much power a house, a city, or a country consumes). This is why we use kilowatts (kW). A kW = 1000 watts). One kilowatt is roughly equivalent to 1.34 horsepower
A kilowatt therefore refers to the rate at which electrical energy is used or generated. For an appliance, kW refers to the rate at which electricity is used to run the appliance. For example, a microwave that has a wattage of 1 kW uses 1000 watts (1 kW) when it is running. When it isn’t running, it uses no power (or next to no power). Similarly, a blender might have capacity to use 0.7kW (700 watts) when it runs, but doesn’t use power when it is not running (you could also think of the blender as using 700 Joules/second). So in other words, we know that a blender has the capacity to use 0.7kW when it is running, but this doesn’t tell us how much energy it has actually used.
What is a kilowatt hour?
A kilowatt hour (kWh) is a measure of energy, like the Joule, a calorie, or British Thermal Unit (BTU). In Alberta, energy consumption is measured in terms of kWh for electrical energy, and with gigaJoules (GJ) for energy consumed from natural gas. In Ontario, electricity consumption is measured in kWh, but natural gas is measured by its volume (cubic metres). Different units are used for different types of energy, but ultimately can be converted from one unit to the other if desired.
A kWh measures the amount of energy equivalent to using one kilowatt over one hour. For example, if you ran your 1 kW microwave for one hour, you would use 1 kWh of energy. If you used your 0.7 kW blender for one hour, you would use 0.7 kWh of energy.
Looking for information about BTU, Amperage, or EnerGuide ratings? Find out about more energy measurement units here
How much energy do my appliances use?
The following table will give you a rough idea of how much energy your appliances use.
| Appliance | Wattage | One kWh of use is equal to... |
|---|---|---|
| Electric furnace | 17,221 W | 3 minutes of use |
| Clothesdryer | 3500 W | 17 minutes of use |
| Dishwasher | 1800 W | 33 minutes of use |
| Microwave | 1500 W | 40 minutes of use |
| Toaster Oven | 1200 W | 100 pieces of toast 50 minutes of use |
| Iron | 1100 W | 54 minutes of ironing |
| Vacuum Cleaner | 650 W | 1.5 hours of cleaning |
| Clothes Washer | 425 W | 3 loads of laundry |
| Laptop | 50 W | 20 hours of use |
| CFL Bulb 60 W equivalent |
18 W | 7 nights of light |
| Wireless Router | 7 W | 6 days of use |
| Cell Phone Charger | 4 W | 278 charges |
Source: General Electric
How Much Do My Appliances Cost to Run?
The table above should help you start to have an idea of how much it costs to run your appliances. You can calculate how much it costs to run certain appliances by multiplying the kWh of energy used to run them by the cents/kWh you pay for electricity. For example, if your 7 W wireless router uses 0.1 kWh electricity per day and your electricity costs 14 cents per kWh, it costs you about 1.4 cents per day. A two-hour diswasher cycle at 14 cents per kWh would cost you approximately 60 cents. An electric furnace, on the other hand, would cost you $33.60 if you ran it for 12 hours a day.
What about GJ, Btu and Amps? Find out about other energy measurements here