Tuesday, 13 June 2017

Reasons why your freezer may be using too much electricity

Back in 2014 I reported some shockingly high energy use in a minority of freezers and fridges [1]. This was from a study of electrical appliances in general and there were only about 130 cold appliances in the sample. Now there has been a much bigger study with 998 fridges and freezers, conducted by BRE [2]. It has confirmed the earlier findings and provided more information as to the causes of the problem. In some cases the appliance was faulty but half the time the main cause was simply running on fast freeze or maximum setting all the time.

This problem mainly affects freezers. 25% of chest freezers were over-consuming and 12% of upright freezers.



How do I know if my fridge/freezer is over-consuming?
When your appliance is working correctly you should hear the compressor humming some of the time. The thermostat turns on the compressor when it gets warm and turns it off when it gets cold. If the compressor is working all the time, or nearly all the time, then there is something wrong. Either it isn’t switching off when it should, or it isn’t getting cold enough.

This chart from the BRE study shows, that overall electricity consumption increases with the %age of time the compressors are running, as you would expect. There is quite a spread because this chart shows all appliance types and sizes – generally freezers use more than fridges and big ones tend to use more than small ones. In most cases the compressor is running less than 60% of the time. The ones running more than 90% of the time are over-consuming; you can see a column on the extreme right of ones that are on all the time, though it is hard to see how many as they lie on top of each other. Out of the whole sample 8% were over-consuming.

Overall consumption by%age of time the compressor is running [2]. From a sample of 998 fridges, freezers and fridge freezers.

Does it matter? Your food could be too warm or too cold.
BRE estimate that the extra electricity consumption could be costing you £50/year or more. In addition your appliance may be running too warm, in which case your food can be spoiling, or too cold, which will make your ice cream extremely hard. They measured the temperature as well as electricity consumption and found overall there were more cases that were too cold than too warm. A freezer should be set to about -18C but there were 9 cases of freezers running at -30C or even colder. At the other extreme there were 2 cases running dangerously warm at -10C or worse.

Reasons for over-consuming.
The BRE engineers investigated in detail a smallish sample of 90 appliances, however this may not be representative as in some cases the appliance had already been replaced before the engineer arranged the second visit. Amongst this sample there were 19 over consuming appliances and the engineers found a range of faults that would make them were run too warm:

  • 9 had dodgy insulation or seals (dodgy door seals were pretty common generally)
  • 2 had a fault in the refrigeration system
  • 4 were in a poorly ventilated place (but so were a lot of other appliances)

The main factors making the appliances run cold were:

  • 10 were set to fast freeze or the maximum setting
  • 3 had a damaged thermostat

Running on the coldest setting wastes energy even if the appliance can manage it.
Not all appliances set to the maximum setting were over-consuming by the 90% rule. However, they were still using more power than necessary. It just means they were achieving the target temperature instead of failing to do so. Among the appliances that were cycling regularly, there was a strong correlation between lower temperature and higher energy consumption.

Age matters too.
Older appliances generally consume more electricity than newer ones. This is mainly due to tightening EU regulations for minimum efficiency. The appliances more than 11 years old consumed 50% more electricity than appliances that were less than 5 years old, on average.

Older appliances were also more likely to be over consuming. In the oldest group, more than 11 years old, 17% were over-consuming compared to 4% in the youngest group, less than 2 years old.

What should we do? Check our appliance settings and, for old appliances, check they are turning off.

  1. If you run a freezer, check the settings and do not run it on fast freeze or the maximum setting all the time. This also applies to fridges too but they use less electricity anyway. For freezers, the recommended temperature is -18C. Fridges should run at about 5C.
  2. If your appliance is more than 10 years old, check the temperature and listen out to see if it is running all the time. If it is, then there is probably something wrong and you could be running an unreasonably high electricity bill.


[1] Is your freezer using more energy than it should? (this blog) July 2014
[2] Study of over-consuming household appliances (BRE) Jan 2017

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