How To Measure The Electricity Usage Of Your Appliances

By Author: Dave Sabri
Total Articles: 29
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If you want to know how much electricity a device uses, simply turn everything else in your house off, leave the device in question to run, and, take two meter readings exactly a minute apart. This will tell you how many units of electricity it uses in a minute of operation, which you can then use to calculate its energy usage over longer periods from a day to a year.

You may not want to do this however, as apart from the inconvenience of it all, you probably do not want to be turning off your fridge or freezer unnecessarily.

It is far easier, and simpler, just to look at the label on your appliance, as nearly everything that can be plugged into the wall has one of these, sometime printed or inscribed directly onto the body of the appliance itself. You can usually find it near where the power cable enters the appliance, or on the body of the AC/DC adaptor.

This label sometimes only gives you a figure for the current demands of the appliance, measured in amps, but you can easily use this to work out the power rating of the appliance simply by multiplying this figure by the supply voltage, which in the UK ...
... can be assumed to be 240v.

DC devices with external transformers usually state the DC voltage required by the device along with the current rating on both the appliance and the transformer. When working out the power rating of a DC device it is important to use the DC voltage rather than the mains voltage in your calculations.

Usually, appliances are designed to be able to work within a set range of voltages, to compensate for differing electrical supply conditions. So an appliance that is set up to work with a 240 volt supply can actually accept any mains voltage from 220 to 240 Volts.

However, if you are calculating power usage, then always use the highest rating in this range for your sums, as it is better to over-estimate the power demands of an appliance than under-estimating them, from a safety and economy perspective.

Some devices can work within a huge range of voltages, such as between 100 and 240 Volts, so that it can be used in any country. For your calculations, however, you should just use the standard voltage for your country, which is 240 in the UK.

Make sure you get the right electricity supply with British Gas, the UK's cheapest electricity supplier on average.