Are energy monitors the best way to measure your power usage?

If you're trying to find new ways to save money by cutting back on your energy use, an energy monitor might help you.

Smart meters measure your gas and electricity use and automatically send the readings to your energy supplier. Your overall home energy use is shown on the smart meter itself, and on a linked in-home display. 

Smart meters and their in-home displays are useful for seeing how much power you might be using each day, or at any one time. But if yours are showing a lot of energy use, it can be difficult trying to figure out which of your appliances is to blame.

Plug-in energy monitors make this more straightforward. 

Want to learn more about smart meters? Read our guide on what a smart meter is and how to get one.

What is a plug-in energy monitor?

As the name suggests, you plug your mains-powered household devices into the plug-in energy monitor and then plug the monitor into the wall socket. It will then tell you how much power is being used. 

You can hook up and measure usage for almost anything that uses electricity, as long as it has a three-pronged UK plug. This includes appliances such as kettles, washing machines, or electric ovens. Power monitors can also measure how much energy several different electronics connected to the same extension lead are collectively using, such as a TV and speaker setup or a desktop computer with multiple screens. 

Using an energy monitor is one of the best ways to be certain how much electricity individual appliances are using. This can potentially help you to work out where money can be saved in the long run.

Alongside plug-in energy monitors, you can also find energy monitors that hook up directly to your home power supply. However, these are generally more expensive and harder to set up. These kinds of energy monitor typically cost more than £60, and require a wi-fi connection and a smartphone to operate. 

For this article, we're focusing solely on the kinds of energy monitors you can plug into a power outlet. 

What is the difference between a smart meter and a plug-in energy monitor?

Both smart meter in home displays and energy monitors show your energy usage.

Both devices can help you to see how much energy you're using and work out how to reduce your consumption. Their difference is a matter of scope. 

Smart meters keep track of how much power an entire home uses per day, week, month, or year, and show it on your in-home display. They are fitted by your energy supplier and send readings directly to it, so you don't need to submit manual readings for your bills. You can get smart meters for both your gas and your electricity supplies. 

A handful of companies break down your energy use by type of appliance in their apps (for example cooking, lighting or washing), but typically can't nail this down by specific appliance. 

Energy monitors measure how much electricity flows through a single plug socket. You don't need a smart meter to use one; you can buy and fit them yourself to check how much energy individual appliances use. You can only get energy monitors for electricity, not for gas. 

Find out more: how to use your smart meter reading data to save on your bills

Why get a plug-in energy monitor?

Which? calculates the average running costs for many widely-used appliances, and publishes them in our guide on how much your appliances cost to run. But while we can calculate average running costs for certain appliances, the actual cost individual households will pay depends on many other factors unique to your usage, home and energy contract. 

Getting your own readings using an energy monitor can provide a clearer picture of how much money you're spending.

For example, we've found big differences in energy consumption between older and newer appliances. If you have old appliances that you suspect may no longer be operating very efficiently, a monitor will give some answers. 

Find out more: What makes a Which? Eco-Buy?

Should I get a smart meter or an energy monitor?

Each serves different purposes, so it depends what you're looking to achieve. It doesn't have to be an either/or choice – you can have both if you want. 

Smart meters are useful if...

You want to keep track of how much gas or electricity your household uses overall. 

With a smart meter, you don't have to take manual meter readings and report them to your energy provider, as the meter will do this automatically. 

Some suppliers have apps that break your energy usage down by category of appliance - such as cooking or heating. But they typically aren't precise about the energy use of specific appliances. 

Even without this, it's possible to estimate the energy usage of certain appliances using a smart meter by looking for spikes in your power consumption when you have electricity-hungry devices running, but this isn't always accurate.

Plug-in energy monitors are useful if...

You're trying to figure out the specific energy usage of individual appliances. 

Being able to get a reading directly from a plug socket can help you figure out which appliances are using the most power without having to do lots of guesswork or maths, as you would when trying to determine the same information with a smart meter. 

With energy monitors, you can get a more precise energy usage measurement and cost per individual electronic device.

What energy monitor features should I look out for?

The best energy monitors aren't necessarily the ones with bells and whistles. Most models are similar. In fact, often, you'll see the same model rebranded across different sellers. 

When buying a plug-in energy monitor, one of the most important features to consider is proper calibration, which will ensure your readings are correct. Energy monitors should be consistent with the manufacturer's own kilowatt-hour readings for various appliances. You should also be able to get consistent results when using other monitors side by side. 

Aside from calibration, two other useful features to have are:

• A built-in display 
• The ability to input your energy unit price directly into the monitor. 

These features give you an immediate and more precise reading of how much something costs to run in your household. This can save you from doing more maths, which is always a plus.

Some smart plugs have energy monitoring capabilities, but they don't usually come with a built-in LCD screen. They require a smartphone and wi-fi connection to function and are primarily used to turn things on and off remotely. 

How can I use the insights from an energy monitor to save money?

Energy monitors can help you identify the appliances that guzzle the most energy, including any that use more energy than you might expect when they're not being actively used. You don't have to buy a monitor for every device in your house to do this. You can leave a device plugged in for just a few days to assess its typical usage, then switch the monitor over to another device. 

You can then use the insights you gather to take action to reduce your household energy consumption, for example by:

• Turning off or unplugging energy-guzzling appliances when they're not in active use. This may not be possible for some appliances, such as fridges or freezers. 
• Replacing old, inefficient appliances with more efficient models. While this will incur a replacement costs, the amount you save in energy over the long term may justify this. Appliances with the Which? Eco Buy recommendation are a good place to start. 

Watch out for exaggerated energy monitor claims 

Treat seller or manufacturer claims about an energy monitor's abilities to save energy and cut your bills with a very large pinch of salt.  

Simply buying and plugging in an energy monitor won't automatically reduce your bills. To do that, you'll need to identify power-hungry electronics and take appropriate action.  

Find out more: Ten ways to save on your energy bills.

Step by step: how to use an energy monitor to measure your power usage

1. Plug your energy monitor into the plug socket, then plug the appliance or device you want to measure into the monitor.
2. Set your electricity unit price on the monitor. You should be able to find this on any bill from your energy supplier.
3. Use your appliance or device as normal. For appliances that are constantly powered on such as a refrigerator or desktop computer, check the reading at regular intervals (eg once a day). Average out daily readings to get a typical cost per day. For appliances that in more intermittent use, such as a kettle or washing machine, you may wish to reset the monitor after each use to make it easier to keep track of cost per use. 

Resetting your monitor can be done by pressing the 'reset' button; some models require you to do this with a metal pin.

Getting readings in this way can also show you the difference between using an appliance in different modes, such as washing clothes at a lower temperature, or running a dishwasher on eco-mode. 

Measuring the combined energy use of multiple devices

If you want to measure how much energy multiple devices use, plug the energy monitor into your wall socket as normal. Then, rather than plugging an individual device into the monitor, plug each of the devices you want to measure into a multi-plug extension. Then, plug the extension lead into the monitor. 

You might want to do this to measure, for example, the combined electricity drain of a TV, set-top box and sound bar. 

How much do energy monitors cost?

While you can find cheap energy monitors for less than £10, we'd recommend checking that they have all the features you need before buying. 

It could be worth paying a little more to get a model that has all our recommended features – proper calibration that provides consistent readings, a built-in display, and the ability to input your energy unit price directly into it.

Find out the annual cost of each of your appliances and get tips on lowering your energy bills with our guide on average appliance costs.

Can I get a free plug-in energy monitor?

All British energy suppliers must aim to install a smart meter in every home as part of a government programme to replace older energy meters. You'll often get an in-home display unit with your smart meter. This shows how much energy your home is using at any one time and how much it's costing, but not the amount that specific appliances are using.

Plug-in energy monitors are not included in the programme, and you'll usually have to purchase one separately. You may find a few suppliers that throw a plug-in monitor in for free in exchange for signing up to specific tariffs, but it's not the norm. 

If you don't have a smart meter or aren't sure if you have one, find out more in our guide to smart meters explained.