To better understand how we measure electrical power, it is essential to become familiar with some key units that are commonly used in everyday life as well as in industrial and scientific applications. These units are the watt, kilowatt, megawatt and gigawatt.
What is a Watt (W)?
It is the unit of power, symbol W, which is equivalent to the power capable of achieving the production of energy equal to 1 joule per second.
Common use: Watts are used to measure the power of smaller devices, such as light bulbs or mobile phones. For example, an LED bulb can use between 5 and 15 watts.
Watt-hour (Wh) and its multiples, such as kilowatt-hour (kWh), megawatt-hour (MWh) and gigawatt-hour (GWh), describe the amount of energy consumed when a device with a specific power is operated for one hour.
What is a Kilowatt (kW)?
The kilowatt (kW) is the unit used to measure electrical power. Its basic unit is the watt (W), which is equivalent to one joule (J) per second. One kW is 1,000 W.
Common use: Household appliances such as ovens, washing machines and air conditioning systems usually have a power output measured in kilowatts. A furnace can have an output of approximately 2 to 4 kilowatts.
Kilowatt-hour (kWh)
This is the unit you will most often find on residential electricity bills. For example, if a 2 kW oven runs for 3 hours, it will have consumed 6 kWh of energy.
What is a Megawatt (MW)?
One megawatt is equal to one million watts. This scale of measurement is used to describe large-scale energy production capacity.
Common Use: Megawatts are commonly used to describe the power output of power plants or large industrial facilities. For example, a small power plant can generate around 10 megawatts.
Megawatt-hour (MWh)
MWh are used to measure energy consumption at the industrial level or for large infrastructures, such as shopping centres or small cities.
What is a Gigawatt (GW)?
A gigawatt, also known as a GW, is a unit of power that is equivalent to one billion watts. The gigawatt is often used as a unit for large-scale power plants or grids.
Common use: Gigawatts are applied in the context of national electricity grids or large renewable energy projects. For example, the installed capacity of a large wind farm can be several gigawatts.
Gigawatt-hour (GWh)
This unit is used to describe large-scale energy consumption, such as in large metropolises, or to measure the output of power plants over an extended period of time.
Practical Examples
To make the concepts of watts, kilowatts and their multiples more tangible when combined with time, let us examine some practical examples from everyday life and on a larger scale:
- Household Use: Suppose you have an LED bulb that consumes 10 watts and you leave it on for 5 hours a day. At the end of the day, it will have consumed 50 watt-hours or 0.05 kilowatt-hours (kWh). If this bulb is used every day of the month, it will consume approximately 1.5 kWh in that month.
- Industrial use: Consider a factory with machines consuming a total of 200 kilowatts. If these machines operate for 8 hours a day, the daily consumption will be 1600 kWh. This is crucial for calculating the energy cost associated with production.
- Energy Production: A power plant that generates 2 gigawatts of electricity for one hour produces 2 gigawatt-hours (GWh). This number can help to understand the capacity of the plant to meet the electricity demand of a large region.
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