The terms ‘watt’ and ‘kilowatt hour’ are often used interchangeably. However, they refer to 2 different concepts. Understanding this distinction will help you better understand how your appliances work and how to read your energy bill.
What does watt (W) mean?
A watt (W) is a unit of measurement for power. It indicates the power of a device or the amount of energy it needs at a given moment.
Although it is often associated with electricity, the watt measures power in general, whether electrical, mechanical or thermal.
Some examples:
- A led light bulb has a power rating of 60 W.
- A microwave oven can have a maximum power rating of 900 W.
The more powerful an appliance is, the higher its wattage. The power rating of an appliance is indicated in the technical specifications or on the energy label.
Units derived from the watt
- 1 kilowatt (kW) = 1,000 watts (W)
- 1 megawatt (MW) = 1,000 kilowatts (kW)
- 1 gigawatt (GW) = 1,000 megawatts (MW)
These units are often used to express the power of household appliances, but also that of larger installations, such as power stations.
What does kilowatt hour (kWh) mean?
This is where we move from power to quantity. The kilowatt hour (kWh) does not measure instantaneous power, but rather the amount of energy consumed or produced during a given period of time.
1 kWh corresponds to the energy consumption of a 1,000-watt appliance operating for 1 hour.
This is the unit you will find on your energy bill.
Some examples:
- A 6 W led light bulb that remains on for 1 hour consumes 6 Wh or 0.006 kWh.
- A 900 W microwave oven that operates for 5 minutes consumes 75 Wh or 0.075 kWh.
Units derived from the kilowatt-hour
- 1 kilowatt-hour (kWh) = 1,000 watt-hours (Wh)
- 1 megawatt-hour (MWh) = 1,000 kilowatt-hours (kWh)
- 1 gigawatt-hour (GWh) = 1,000 megawatt-hours (MWh)
What can you do with 1 kWh?
To give you a concrete idea, 1 kWh is enough to:
- Run a refrigerator for 24 hours.
- Watch television (LED) for 10 to 15 hours.
- Travel approximately 5 to 7 km in an electric car.
- Leave an LED light bulb on for nearly 100 hours.
Here is a list of electrical appliances with their power (in watts) and consumption (in kWh).
In a nutshell
- Watts indicate the power of an appliance.
- Kilowatt hours indicate the amount of energy consumed by the appliance.
A high-powered appliance does not automatically consume a lot of energy: the duration of use plays an equally important role.
If you know the power and duration of use of an appliance, you can easily calculate its consumption yourself.
Did you know?
The terms “watt” and “kilowatt hour” are named after James Watt, a Scottish engineer born in 1736 who became renowned for his improvements to steam engine technology.