Saturday, 13 October 2012

Energy efficient appliances - the ratings confusion

When you buy a new washing machine, or freezer or other electrical appliance, it's good to look at the energy rating to see how efficient it is, because this will affect your home energy consumption and hence bills and carbon emissions. The  EU energy rating class, originally A-G with A as the best, is only part of the energy certificate - for washing machines this tells you about water usage, spinning efficiency and noise, for example -  but most people don't look at at the rest. However, the classes can be confusing because they depend on the appliance size and features as well as power use. I recommend you look instead at the estimated annual energy consumption.


Size matters

For some appliances size matters a lot.

For a TV, the size of the display is the most important factor. A 40" TV can take nearly 50% more power than a 32" with the same rating and a 46" TV can take double the power. For a B rated device (there aren't that many As yet) that's an extra 30W for the 36" or 55W for the 46".  Over the year, at 4 hours a day, that means an extra 43 kWh/year for the 40" and 81 kWh/year for the 46". 

Size matters for fridges and freezers too, and also shape - an A+ 300 litre chest freezer should use 32 kWh/year less than an upright freezer of the same size. However, depending on the shape of your kitchen you may have little choice.

Washing machines, don't vary so much in size but there is still a difference - an 8kg machine may use 12% more energy than a 7kg machine with the same rating. An 8kg A+++ uses the same energy as a 7kg A++.

For ovens, the rating calculation is based on a size category and there are only three categories - small, medium and large. A medium oven can be anything from 35 to 65 litres [1].


Features matter

For TVs, one with a built in DVR is allowed some extra power to allow for the extra functionality. In the B rating class this amounts to another 4W on active power consumption which isn't much - but it typically also means higher power when you aren't watching, because the standby mode has to be able to leap into action for recording. The standby power consumption is not part of the energy rating class calculation, though it is taken into account for the annual energy consumption. (Standby power consumption is included in the energy rating for washing machines and dishwashers but not for TVs).

With fridges and freezers, there are energy allowances for frost free function and also for built-in appliances which are narrower than 58cm. A frost free freezer is allowed to use as much energy as a basic freezer which is 20% larger. For a 210 litre upright freezer, the frost free function has an allowance of 21 kWh/year and for a 300 litre upright freezer the allowance comes to 30 kWh/year.

'A' rating isn't necessarily the best

Energy certificate layout (washing machine)
Since the energy ratings were defined, standards for some appliances have improved a lot. You can now get A+++ freezers and washing machines. An A+++ washing machine will use a third less energy than a similar sized A rated machine and an A+++ freezer  uses less than half the energy of a similar A rated one. For a 300 litre capacity upright freezer, the difference is more than 200 kWh/year.

When you look at an energy certificate (as shown) it is obvious which is the best available rating but when you are comparing products in online shopping it isn't always clear as the product specification just lists the energy rating class.

Estimated annual energy consumption

The appliance energy certificate will always show the estimated annual energy consumption - based on typical usage - and you can usually find this on the appliance specifications when shopping online too.  This is a useful figure but you can't just assume it will be accurate for your household.  For fridges and freezers the estimated energy use should be reasonably fair depending on the ambient temperature where you put it. For other appliances you need to know what is regarded as typical usage. For example:
  • TVs - 4 hours/day 
  • Washing machines 220 cycles/year (4.2/week)
  • Dishwashers 280 cycles/year (5.4/week)
 For example if you are only going to run the washing machine twice a week your energy use will be half the estimated figure.


Not all appliances have energy ratings

Video games consoles don't have energy certificates and nor do gas ovens, though electric ovens do. Unfortunately, when manufacturers don't have to provide a certificate it is much harder to find out how much energy they use. Sometimes you can find what you need in 3rd party reviews like this one from engadget about games consoles.

Video games can be a serious energy hog - the first Play Station 3 consumed more than 200 W, not counting your display screen which could be another 100 W, and they don't go into standby automatically when you don't use them for a while.  The Nintendo Wii with Connect 24 enabled uses 9 W even on standby, though if you turn that feature off it uses only 2 W. Later versions of the Play Station 3 use less power so it seems that Sony does recognise that consumers are concerned, even though they don't advertise the power usage information on their product specs.

Final remarks

When I was on the Transition Cambridge Energy group stall in a shopping centre recently we asked visitors if they consider energy efficiency when buying new appliances. Most people said yes, but it wasn't usually the most important thing - functionality or price is more important. The price issue is a complex one because you have to balance the benefits of savings now versus extra costs later. The functionality issue is more subtle.

The EU energy ratings effectively hide the implications of our choice of functionality on energy consumption. Seeing two TVs, both 'A' rated, you could probably guess that the bigger one will use more power but could you guess how much more? Also, I only found out by accident that a frost free freezer will use more energy than one without that feature. And even though I know it now, I'm not sure I'll remember it when I'm in the shop and looking at a product spec. Seeing the words 'frost free',  I'll be thinking how tedious it can be to run a manual defrost. I won't be thinking of the kWhs. Overall, even though the energy ratings do have a sort of logic they aren't straightforward to use. The estimated annual consumption figure is a better guide most of the time.


The EU energy ratings are defined in EU regulations such as these:

[1] Cookers from
[2] Electricity consumption and energy savings potential of video game consoles in the United States

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