Term: Kilowatt-hour (kWh) Definition

Kilowatt-hour (kWh) Definition

A kilowatt-hour (kWh) is a unit of measuring electricity and is defined as one kilowatt of power sustained for the period of an hour. Kilowatt-hours are the common unit of measurement for many electric utility companies and electricity suppliers.

How Is a kWh Measured?

In order to fully understand how Kilowatt-hours are measured in real life, one must grasp the concept of electrical demand vs. electrical usage. Electrical demand is the total capacity of electricity that a given appliance, device, or motor uses at any given moment. For example, if you have a 100 watt light bulb screwed into a light socket at your home, and you turn on the light, that bulb will demand 100 watts of power from the electrical meter. The duration of the light being on does not affect demand. Whether the bulb is left on for a millisecond or it is left on for five hours, it will still only demand 100 watts of power due to its capacity.

Electrical usage, on the other hand, calculates the total amount of electricity demanded over a period of time. In colloquial language that electricity demand over time is known as usage. For example, if you have ten light bulbs in light sockets at your home, and each light bulb is 100 watts, those bulbs represent 1,000 watts of electrical demand when turned on.

Since a Kilowatt equals 1,000 watts of power, when those ten bulbs are turned on and left on for one hour, you will consume 1 kilowatt-hour (kWh) of electricity usage. A kWh is a unit of energy that measures the amount of power being consumed in a home or building over a period of time. When your home uses 1,500 kWh of power in a given month, that means you had 1,500 kilowatts of power turned on for an hour, or you had 15 kilowatts of power turned on for 100 hours, or you have 1.5 kilowatts of power turned on for 1,000 hours.

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