How to Measure Power Consumption with a Multimeter

Power consumption is a crucial factor to consider when evaluating electrical devices and their impact on energy usage. Measuring power consumption accurately can provide valuable insights into energy efficiency and help identify potential energy-saving opportunities. In this blog post, we will guide you through the process of measuring power consumption using a multimeter, a versatile tool found in every electrician's toolbox.

What You Will Need

  • A digital multimeter (preferably one with True RMS capability)
  • A power source (such as an electrical outlet or battery)
  • An electrical device for testing

Step-by-Step Guide

Follow these steps to measure power consumption:

  1. Start by preparing your multimeter. Set the meter to the voltage measurement mode and ensure it is properly functioning.
  2. Next, plug the electrical device you want to measure into the power source. Make sure the device is switched on.
  3. With the multimeter still in voltage measurement mode, carefully insert the multimeter probes into the power outlet or connect them in parallel to the device's power cord.
  4. Observe the multimeter display. It will show the voltage value of the power source.
  5. If your multimeter has a True RMS function, enable it to obtain a more accurate measurement, especially for devices that draw non-sinusoidal currents like computers or modern electronics.
  6. Now, let the device operate for a specific period, preferably at least an hour, to obtain a representative reading of its average power consumption.
  7. After the required time has passed, check the multimeter display again. This time, it should show the current (in Amps) drawn by the device.
  8. To calculate power consumption in Watts, multiply the voltage value obtained earlier by the current value displayed now.


1. Can I measure power consumption with an analog multimeter?

No, measuring power consumption requires a digital multimeter capable of reading AC voltage and current accurately.

2. Why is it essential to use a True RMS multimeter?

A True RMS multimeter accurately measures the root mean square (RMS) value of an AC signal, giving precise results even for non-sinusoidal waveforms.

3. Is it necessary to let the device operate for an extended period?

Yes, to obtain an accurate average power consumption reading, it is recommended to let the device operate for an extended period, typically an hour or more.

4. Can I measure power consumption of DC devices?

No, the process described in this blog post is suitable for measuring the power consumption of AC devices only.

5. Can a multimeter be used to measure power consumption of an entire building?

No, multimeters are designed for measuring individual device power consumption. To measure an entire building's power consumption, specialized equipment like energy meters should be utilized.

We hope this guide helps you measure power consumption accurately using a multimeter. By understanding the energy usage of your electrical devices, you can make informed decisions to optimize energy efficiency and reduce unnecessary power waste.