SEED Science

How does a domestic electric meter work?

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How does a domestic electric meter work?

How does a domestic electric meter work?


An electric meter is designed to measure the total amount of electrical power consumed in a house, usually in kilowatt-hour (kWh). Electrical power is measured in watts (W), which is the product of the amount of electrical current in amps (A) times the voltage in volts (v). Thus, an appliance using 5 amps at 220 volts would consume 1,100 watts, or 1.1 kilowatts (kW). Similar power information can be found on most appliances. 

Continuing with this example, if this appliance was to be used for one hour, it would consume 1 kilowatt-hour (kWh) of energy. This value is measured by the electric meter on attached to a house, and that is how an electric meter works.

Types of electric meters

A traditional electric meter typically consists of two parts: a transducer to convert the power into a mechanical or electrical signal, and a counter to display the value of the total energy that has passed through the meter. A small amount of the total current being used is shunted away to turn the counter. The number of revolutions of the counter is proportional to the amount of energy used.

A more recent electric meter relies on solid state circuitry. A microcontroller monitors all electricity usage and calculates the amount of energy used. There are no moving parts, and the energy consumption is displayed on a liquid crystal display (LCD) screen.

PlanetSEED has fun activities that teach students about electricity.