Energy monitors: Smart meters and energy monitors explained What is an energy monitor?

Energy Monitor

Energy monitors can help you understand and reduce your electricity usage.

If you don’t know the difference between energy monitors and smart meters, you’re not alone. Our survey of almost 2,400 Which? members (June 2010) found that a third of our members think they are the same thing.

However, energy monitors and smart meters are actually very different, and this guide will help you understand the crucial differences between them.

Energy monitors – what do they do?

Energy monitors are simple handheld or tabletop gadgets that give you an estimate of the amount of electricity you are using in real time.

They are also known as home energy monitors, electricity monitors and electricity usage monitors. Widely available, they cost around £40 (or free from some energy suppliers) and you can install them yourself.

Most energy monitors allow you to view your real-time electricity usage in units of energy used (kWh), cost or carbon emissions. Some have additional features, such as allowing you to set daily electricity usage targets or alarms to alert you when you have used a set amount of electricity.

Energy monitors are designed to help you keep track of your electricity usage, discover how using different appliances affects your energy bills and, ideally, help you to cut your electricity consumption.

In our tests we've found that some energy monitors are better than others at accurately and consistently displaying information in a useful way. Take a look at our energy monitor reviews to find the best one.

Energy monitors – what don’t they do?

Energy monitors don't send information to your energy supplier, though many people mistakenly believe that they do.

Most energy monitors do not measure your gas usage, though the Saveometer from Eco1 Limited (launched in March 2011) does promise to show your gas usage if you buy the additional gas transmitter. We haven't tested the gas transmitter but you can see how the main electricity monitor scored in our tests by visiting our Saveometer review

One in five of the Which? members we surveyed wrongly thought that energy monitors could send information directly to your energy supplier. In fact, only smart meters can do this – see What is a smart meter? to find out more.

The EDF energy kit

Most energy monitors are made up of three parts: a handheld display, a transmitter and a sensor

How do energy monitors work?

Most energy monitors are made up of three parts: a handheld display, a transmitter and a sensor.

The sensor clips on to a power cable connected to your electricity meter box. This monitors the magnetic field around the power cable to measure the electrical current passing through it (amps).

Once you’ve attached the transmitter to the sensor, it will send the information wirelessly to the handheld visual display unit, where it will be re-calculated and displayed as real-time power usage (in kWh), cost (£) and greenhouse gas emissions (tonnes of CO2).

Where can I get an energy monitor?

You can buy energy monitors from many high street shops – including Argos, John Lewis and Tesco – and there are several well-known energy monitor brands, such as OWL and Efergy. Different products offer different levels of functionality, and vary in price from around £20 to £100.

We’ve tested several energy monitors, and rated them for accuracy and ease of use - we've found that you don't have to spend a lot to get a Best Buy. Find out which energy monitors we rate as Best Buys in our energy monitors review.

Free energy monitors

You can also get a free energy monitor if you sign up to certain energy tariffs, such as British Gas’s EnergySmart tariff or Southern Electric’s iplan tariff.

However, head of switching at Which? Switch Tom McLennan advises: ‘Before switching to an energy tariff to get a freebie, make sure you’ve carefully weighed up the value of the freebie against the cost of the tariff.

‘In some cases you may be better off switching to a cheaper energy tariff, and buying an energy monitor separately. You can find the cheapest energy tariffs available to you by entering your postcode and a few simple details into the energy tariff calculator at Which? Switch - the average saving is around £250 a year.’

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