Updated: 03/05/2023 by Computer Hope
Suraielec plug-in wattmeter.

A wattmeter is a tool used to measure the flow of electrical energy through a circuit in watts (W). More plainly, a wattmeter tells you how much power any attached device uses in real-time.

In addition to showing current power drawn from a wall plug, many wattmeters calculate power consumption over time and can estimate the cost to run a device based on annual electricity rates.

How does a wattmeter work?

A digital wattmeter (shown right) measures power by sampling amperes and volts several thousand times a second. As these values are sampled, they are multiplied by one another to get watts at any given instant.

Electronics terms, Measurements, Multimeter, Power terms, Tools