Energy monitors: How we test energy monitors

Energy monitors

Only the very best energy monitors can be Best Buys

We think a good energy monitor needs to be accurate and consistent, but because it requires you to change your behaviour in order to cut your energy use, it also needs to be easy to use and display information in a useful way.

When we test energy monitors, we put them through thorough lab tests to ensure they perform well in all these areas – and only awarded Best Buy status to the very best models.

Our test scores ignore price and are based on:

  • accuracy, consistency and frequency of signal transmission – 50%
  • ease of setting up and everyday use – 50%.

Energy monitors must score 70% or more overall to become a Which? Best Buy.

Accuracy, consistency and frequency of signal transmission tests

To test the accuracy and consistency of each energy monitor we attach each monitor to an electricity-supply cable, like the one going into your electricity meter at home, and challenge it to report energy usage at a variety of levels – from 100W to 6kW.

The accuracy score shows how accurately each model reported the actual energy use and the consistency rating is based of the variability of readings. A good energy monitor will be accurate and have low variability in readings, so the numbers you see are a reliable indication of the electricity you are using day to day.

We also measured how frequently the transmitter sends information to the display unit and found this varies from around every two seconds to every 12 seconds, depending on the model. The energy monitors that transmit more frequently are preferable for speedy feedback.

Ease of setting up and usability assessment

When rating energy monitors for ease of use, our lab tester looks at a wide variety of factors. These include:

  • how easy the energy monitor is to set up (including understanding the instructions, attaching the sensor/clamp around the electricity supply wire, pairing the transmitter with the display unit and inputting tariff information)
  • the quality of the information displayed (including whether the data shown on the display is clear and easy to understand and how easy it is to move between different options on-screen)
  • ease of using historical data (including whether the historical data is easy to access and whether it is easy to understand).

While all energy monitors offer similar basic functions, we found that some are much better designed than others to help you take action. Some models display information in a much more useful way than others and the quality and clarity of historical data varies quite significantly.

You can see which models we made Best Buys in our full energy monitors review, plus here you can use our compare energy monitor features tool to find models that performed particularly well in the areas that are most important to you.

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