/ Home & Energy

Energy monitors – spend a little to save a lot?

Energy monitor on coffee table

We’ve just tested energy monitors in the Which? lab and found Best Buys from just £35. But is this still too much to spend? Is it worth splashing out on these gadgets or are they a waste of time and money?

The most revealing thing we found in our energy monitor tests is just how different each model is.

While some are designed brilliantly and offer a wealth of handy usage data, on one pricey monitor all you could see was your current usage in watts and an estimated annual cost. This was based on keeping all your appliances on all the time – an irrelevant and fairly useless figure if you ask me.

Monitors don’t benefit everyone

So clearly, some energy monitors will be much better at helping you cut your energy bills than others this winter. But are even the very best performers – our Best Buy energy monitors – worth splashing out on?

I think it depends on how much you’ll use one. An energy monitor itself won’t cut your bills – it relies on you using the information it provides to actively change your behaviour.

When we sent monitors to five Which? members to try out, they had varying degrees of success. Some loved the insight into their usage and changed their behaviour significantly, but others reported that they were already doing pretty much all they could to save energy, so the monitor made little impact (read their full verdicts in our energy monitor user reviews).

It takes time to save money

I have to admit to a little inaction when it comes to energy monitors. I tried one out in my old flat and enjoyed running around turning things on and off and watching the figures jump around. And seeing how much energy the oven used certainly made me think twice about slow roasting!

However, I’ve been in my new flat for just over two months now and still haven’t set up the energy monitor. It’s lazy, but finding out that our electricity meter is in our neighbour’s garden just made it seem like too much hassle…

So is my energy monitor saving me nothing at the moment? Well I have kept the knowledge I gained in round one. Once you understand your energy use, all energy-saving actions can be done without an energy monitor, so hopefully my bills aren’t as high as they could be.

And maybe I’ll plug my energy monitor back in one day. I never really got to grips with the historical data, but our testing has made me keen to try again. Perhaps the long-term benefits of energy monitors – such as being able to log and monitor your usage over weeks and months – make them more worthwhile?


Maybe useful in tracking down unusual or seemingly high electricity usage , but for most people reading the meter everyday for a week or so should give the same information.
Anyway for many its the gas fired heating which is the prime candidate for making savings on.

We recently acquired free of charge from Npower the Efergy Elite energy monitor, a Which Best Buy. It has already saved us hundreds of pounds per year.

Early one morning a few weeks ago my wife and I removed all the fuses in our house, replaced them one by one and religiously tested how much power each appliance actually uses, storing the results on a spreadsheet, so that we were made totally aware the impact each appliance makes.

But when we inserted the lighting fuse we noticed an immediate usage of 150 watts even though there were no lights switched on inside or outside the house. After a long investigation we found a light switch in our garage that is attached to a redundant fluorescent fitting with no bulb! When the switch was on it used 150 watts even though there has been no bulb for at least 10 years. The power was leaking away through the old lamp starter circuit (and this can happen even on a working lamp). 150 watts on my tariff costs £170 per year so could have cost us the equivalent of £1700 over the last 10 years!

Needless to say all my strip lights have now been replaced with energy saving lamps.

I believe one of the benefits of an Energy Monitor is to show you how much energy you use when appliances are on standby, say, during the night, as this is a constant drain 24 hours per day, 365 days per year. By concentrating hard on which items can be switched off and not just left on standby we have been able to reduce our overall consumption by around another 100 watts per hour, or £113 per year (and this is while we are asleep)

If you can be bothered putting in the time & effort using an Energy Monitor it will pay you back handsomely.

I’ve had an energy monitor for about 2 and half years now.
It’s actually pretty useless really if you are willing to put in the effort that rarrar and Colin (above) and I already have done: Every appliance has a rating shown on it. This is usually quite easy to find. If you know the rating then you can set up a spreadsheet like Colin refers to. I did this about 7 years ago when I was looking at whether Economy 7 would save me money.

If you simply pull out the plug of all appliances when they are not in use, and certainly before you go to bed or go out, leaving only things like the fridge, freezer, VCR or DVD recorder (if you have it set to record), aquarium (if you have one) and electric clocks (if you have any mains ones) then you have no interest in standby usage and are guaranteed not to consume more than you expected on standby. You also reduce by a vast amount the risk of fire in your home. (In fact most of my appliances are so old that they don’t even have standby so for people like me pulling the plug is a matter of routine and nothing new to get used to).

If, like Colin, you have a redundant appliance or fitting (like his garage light) you should have it permanently unplugged or disconnected for safety. Colin’s light fitting must have had a major fault to earth to use 150 watts with no tube in (I am qualified in this area, I’m not just making this up) so in fact it posed a shock (and possibly fire) hazard for all that time it had been left on. However, identifying such unknown faults is one GOOD use for an energy monitor and if, like Colin, it prompts you to get the fault rectified, it may also be a life saver.

Reading your meter regularly (like Rarrar suggests) is also very effective. This is also usefuk in identifying a meter fault: meters DO read “fast” and “slow” sometimes and they DO go faulty. Your energy monitor won’t show you that but regular meter readings will draw this to your attention. You can then get the electricity company out to replace the meter. (And this is worth doing even if the meter is reading “slow” and you are being UNDER charged, because if the energy company finds out about the fault later, they will estimate how long it’s been faulty for and expect you to pay up for the estimated extra energy you’ve used over what it said. Legally you have to pay at least some portion of this, even if you try a court battle first, so it’s in your interests to have an accurate meter at all times.)

In my case I set up my spreadsheet and read my meter at 11:30 p.m. and again at 7:30 a.m. every day for 6 months (spanning Jan to June one year) to see if I would benefit from Economy 7. My “base load” is around 450 watts because there is a fridge, freezer, aquarium and three ponds with filtration which are running 24/7. At the time of my experiment it was as broad as it was long to have E7, so I didn’t bother changing.

I bought my energy monitor just after buying a washer which was supposed to be energy saving trust recommended: it very quickly became apparent that my 25 year old machine had been using much much much less than a quarter of the electricity hat they new “energy efficient” one did. I bought the monitor to assist in a battle with trading standards, the manufacturer of the washer and the Energy Saving Trust, which resulted in the EST admitting that they knew that all new washers, and other new appliances, use more energy than their old counterparts, but they (the EST) only test agains other current machines not against old models. My Energy monitor therefore helped me to extract this admission from EST but the manufacturer still refused to offer any support so the new washer was sent to scrap and a reconditioned very old one bought which uses less power.

This leads me to one final point: keep old appliances until they are no longer serviceable: new ones may come with green claims but as you can see from the EST’s admission to me, these claims are not always what you might assume them to be.

So, in summary, I think energy monitors are only really of any use to people who don’t actually know how to read a meter and / or don’t really know what their appliances are rated at.

Richard says:
30 December 2010

I haven’t bought an energy monitor because I am very sceptical about the practicalities of its use. I have tried to quantify the issue for my home by doing a quick count of the energy using devices. The totals came to:-
41 independently switched lights
22 permanently wired devices
40 devices permanently plugged in
23 devices plugged in occasionally

This is only the start of the problem. Most of the devices will have multiple modes of operation, many of them not under direct user control. A few examples are:-
• A washer/drier with 20 programmes, 12 of which I have used. Most of these programmes have multiple phases. There are also 5 independent buttons that control global modifications to some of the programmes.
• Fridges and freezers that may or may not have their compressors running at any one time. This will depend on such things as the ambient temperature, whether fresh food has been put into them, and whether the fast freeze button has been pressed.
• Chargers for rechargeable devices that detect when the device is fully charged.
• Central heating systems where the pump and 3 way valve will operate according to demand.
• TVs that vary their screen brightness according to the ambient light.
• PCs and all-in-one printers that vary their consumption depending on which components are active at any one time.
• Devices which have a standby mode, or perhaps more than one stage of standby. Some devices with an on/off switch will also use power in the off mode unless they are switched off at the mains.
• Toasters that use different amounts of power depending on how many slots are in use.

There will also be an annual churn of devices and light bulbs, as they either come to the end of their natural lives or when new types of device come along.

I know our household size (4) is larger than the average (2.4) and also our house is larger than average (a 5 bedroom semi). However, the figures still suggest that the average household would have to undertake a large programme of controlled experiments if they were to try to calibrate each device. The person doing the testing is unlikely to increase their popularity with other household members, given the disruption all this would cause.

I can’t help feeling that the current style of energy monitor is best suited to a person living alone in a small flat and with a lot of time on their hands.

David Huggins says:
30 December 2010

I have had an energy monitor, supplied by our (previous) supplier, Scottish energy, for some two years now. This has been useful in identifying the cost of keeping lights on un-necessarily, but as we are almost entirely on low energy bulbs savings have been minimal. However, comparing the consumpt as recorded on the monitor with that from meter readings, the meter shows an average consumpt 25% higher. We had a replacement monitor, also supplied from Scottish energy, but the same difference in consumpt is evident.

The monitor looks very like, but not quite identical to, the Current Cost Envir. Is a difference of 25% in accuracy acceptable, or is this an indication that we should be asking our supplier (now OVO energy) to replace our meter?

There are too many variables in a standard household to be able to give a 100% firm answer to your question, but in my opinion, with my qualified electrician’s “hat” on, I would say that a variance of around 25% is way too high to be ignored and I would recommend that you at the very least ask OVO to investigate. If they disagree that the meter is faulty you can still insist on having it taken and tested, although if the test reveals that the meter is NOT faulty after all, you will have to pay for the test, so it’s worth asking what that fee would be to be sure of exactly what the worst case scenario is.

My suggestion would be:
1) ask OVO to investigate
2) if they seem reluctant or if they insist the meter is NOT faulty, ask OVO to send one of their own advisors to check that you have set up the energy monitor correctly. If they find that you have not, then you have probably found the cause of the discrepancy, but if they feel that you HAVE set it up correctly you should be able to insist on them changing the meter.
3) if the above 2 stages fail, ask OVO for a quotation for having the meter tested and before you decide to go ahead take this quotation to Citizen’s Advice and / or Trading Standards. If they feel the quotation is reasonable, go ahead. If they do not ask them to guide you or take over your case to get OVO to act further.
4) unless it is proven that you set up your monitor incorrectly AND that you meter is NOT faulty, you should then set about seeming financial compensation from OVO. You will not be able to determine exactly how much you have over paid, nor for exactly how long, so you cannot expect to get everything that you may feel is due to you, but you should be able to reach an agreement with OVO on a sum that will be repaid.

I have never traded with OVO and have no idea what their reputation for customer service is like. I strongly suggest that you keep a detailed record of everything that you do and everything that OVO staff say to you in case at any stage in the process they attempt to charge you for any of the investigation or work.

Good luck.

Penny says:
2 April 2011

Energy monitors are helpful when you first obtain them. We found the halogen lights to be the biggest user of electricity. Three rooms each with a minimum of 3 x 50watts really crank up the wattage and you never give it a thought. We are now trying to purchase some new low wattage versions that give the same light but use less electricity but they aren’t easy to find and can be very expensive. Also we are looking (unsuccessfully) for the plugs into which you can place individual appliances to check their usage. Again, these have been ‘out of stock’ on many web sites for months and months. So, monitors can be useful appliances but trying to solve the issues raised can be fraught with disaster.

Robert E Wright says:
20 November 2012

I bought an energy monitor because I like geeky things! I find it does encourage you to turn the heat down and lights off in unused rooms. I find it useful.