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Energy monitors

energy monitor

This guide is intended to provide general guidance only. It is not intended to give you advice on your personal financial circumstances. You should seek independent professional advice if you’re unsure about anything mentioned in this guide or what choices to make.

Ever looked around at all your electrical devices and wondered which one uses the most energy?

Or wondered what the difference is between switching your television off at the wall and leaving it on standby?

Want to cut the cost of your electricity bills?

If you answered ‘Yes’ to any of these questions, what you need is a home energy monitor.

What exactly is an energy monitor?

A ‘whole home’ energy monitor is made up of three units:

  1. A small hand-held or table-top device with a screen that shows you how much electricity you’re using in your home – some models also allow you to receive the information on your mobile phone, tablet or laptop
  2. A sensor unit that clips on to a power cable connected to your electricity meter – this monitors the magnetic field around the power cable to measure the amount of energy you’re using
  3. A transmitter – this sends the information wirelessly to the hand-held device so you can read it on the screen

You can also get more basic plug-in monitors for measuring the energy used by individual appliances – but only if they plug into a wall socket.

How would a home energy monitor help me reduce my energy use?

Your energy monitor should show you how much energy you’re using, how much it costs, and the level of your greenhouse gas emissions.

The best energy monitors let you walk round your house switching items on and off, to see how much energy each electrical device or appliance uses.

It can also show you how much your energy is costing you, and how much you’re saving once you start using your energy more efficiently.

Some models allow you to set daily electricity use targets or have alarms to let you know when you’ve reached a certain level of use.

How much money would an energy monitor save me?

The energy monitor itself can’t actually save you money; it’s the way you use it that counts.

It can help you to understand how much energy you’re using, which appliances are costing you most, and how much you could save by switching things off or using them less.

According to the Energy Saving Trust, using an energy monitor could reduce your energy use by 5% - 15% in just a year. So if your annual electricity bill is £600, you could save between £30 and £90.

How should I start using my home energy monitor?

Once you’ve installed your home energy monitor, it’s fun to try it out at once. Go round your home and switch off everything you can – though probably not the fridge and freezer.

Then walk around each room holding your energy monitor, and switch things back on as you go. If your model has a battery-powered hand-held unit, you can walk around freely. If it only works off the mains, you’ll need to plug it in and unplug it as you move from room to room.

You’ll see the monitor reading increase when you switch on a new appliance. Some models will transmit this information in a couple of seconds, others may take up to 12 seconds, so make sure you wait long enough.

It’s a great way to find out which appliances or rooms are costing you most, and some of your discoveries could be quite a shock.

Write down what you’re finding out, so you can use the information to help you make cost-cutting decisions.

Most importantly, when you’ve done this, don’t just put your home energy monitor away and forget about it. You need to get into the habit of using it regularly, to make sure you don’t slip back into expensive habits. Get the whole family into the habit of checking their electricity use and switching off to save energy.

Are home energy monitors completely accurate?

Some are more accurate than others. Choose one that measures actual power, shown in watts, rather than one that only measures apparent power, in volt-amps.

If a monitor only measures apparent power, it will be less accurate when it’s trying to gauge small amounts of consumption – less than 100 watts, for example, and particularly at less than 60 watts.

Your provider will charge you for actual power, measured in kilowatt hours, so it’s better to know how much actual power you’re using.

Find out more about kilowatt hours here

If you want to measure the amount of energy used by individual appliances that are plugged into a wall socket, you could get more accurate readings with a plug-in monitor (see next question). However, ‘whole home’ energy monitors can measure devices that don’t have plugs – like lights, burglar alarms or showers – although it can’t measure them individually.

What is a plug-in monitor?

A plug-in monitor is a more basic device that only measures the energy use of one appliance at a time. You simply plug it in between the appliance’s own plug and the electric socket. It can then tell you how much energy that individual item is using.

If you want to find out how much energy a group of appliances is using, such as a laptop, router and printer, you can plug a multi-socket adaptor or extension lead into the monitor.

Can I install an energy monitor myself?

Yes – you don’t need to be a qualified electrician. For most models, you’ll just need to attach the sensor unit to your meter and then tune the transmitter and hand-held unit so they can communicate with each other.

Does my home energy monitor send information to my energy provider?

No – the figures it shows are purely for your information. If you have an agreement to give your provider regular meter readings, you’ll still need to do this.

That’s one of the reasons why at OVO we recommend using a Smart Meter rather than an energy monitor. It shares information about your energy use with us, saving you the effort of giving us regular meter readings.

How do I know which energy monitor is best for me?

There are all kinds of energy monitors available, from very basic cheap plug-in ones to highly sophisticated expensive versions, so it makes sense to have a look at as many as possible before you buy one.

The best energy monitors will include:

  1. A display showing how much energy you’re currently using
  2. A portable battery-powered unit that you can move around your home
  3. Wireless connection to the unit attached to your electricity meter
  4. A facility that lets you check on historical data, including your daily, weekly and monthly figures

How much do they cost?

You should expect to pay from around £28 for a very basic model to £150 for a high-tech device that could also tell you how much energy your solar panels are producing.

Do some energy companies offer free energy monitors?

Yes – a few suppliers do offer free energy monitors, but you should carefully check the cost of the related tariff against the value of the free monitor, as it may not turn out to be much of a benefit in the long term.

We don’t offer free energy monitors at OVO, because we believe our Smart Meters, with their In-Home Displays, offer the same information but with extra benefits. So if you’re an OVO customer and you want to monitor your energy use, just get in touch to ask us if you can upgrade to a Smart Meter.

How can I reduce the amount of energy I use?

If your home energy monitor has convinced you to cut down your energy use, here are some ideas:

  1. When you boil a kettle, only use as much water as you need
  2. Turn appliances off at the wall – don’t leave them on standby
  3. Use energy-saving light bulbs
  4. Defrost your freezer regularly
  5. If your boiler’s more than 15 years old, look into replacing it with a more energy-efficient A-rated condensing boiler
  6. Slip an insulating jacket on your hot water tank – you could save around £35 a year
  7. When using your washing machine, never set it higher than 30˚




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