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Revelations of a smart meter

Denis McMahon
Our so-called energy supplier was e-mailing its customers, asking if they were interested in having a smart meter fitted.


So I said, "Yes." (Somebody needed to.)


So now we have a smart meter.


It has been interesting to find out which appliances guzzle the most energy. It isn't lights. Not computers. Not even washing machines. Forget TVs on standby.


It's refrigerators.


We have a fridge-freezer and a separate larder-fridge. These have their ratings stamped on a metal label inside - 230 W and 90 W respectively.


The big revelation is the proportion of the time these fridges spend consuming that amount of power. In a hot summer's day they seem to be running almost continuously at that rate. On a cool autumn morning the consumption may be down to less than 100 W in total,  but open those fridge doors to grab something for breakfast and the power is soon rising.


Even the dishwasher and washing machine seem to compare favourably, consuming around 250 W most of the washing cycle. They peak into the kilowatts during heating phases but these last only a few minutes. And of course they do not run 24/7 like fridges.


These fridges are fairly old, and clearly I am considering their replacement, though they still work. Advice percolates in that newer fridges are much more economical on energy. I am willing to believe that is the case, but as an engineer I like things to be quantified. Most engineers are economists at heart and I should like to prepare a "business case" for replacement, and work out how long the saving in energy will take to pay for the replacement.


So how much power does a modern fridge-freezer consume?  I visited the web site of a well-known retailer of electrical appliances to see what I could find. Details were given of energy consumed in a year for various fridge-freezers, but no actual power rating. I went in-store to browse around. I peered at one fridge-freezer and opened a door, looking for a rating label but could not find one. A friendly assistant came up and asked if I needed any help. She suggested that I noted the catalogue number then went online and I should find the detail I sought. Back home I tried that but still could not find a power rating. I went to the websites of three different manufacturers of fridge-freezers. Again, all gave the vague estimate of energy used in a year but none gave a power rating.


I like to get down to fundamentals when I am evaluating. I sometimes wonder how these estimates of energy usage per year are arrived at. There must be many unknown factors affecting this, e.g. how warm is the room where the fridge is kept, how often is the door opened, what is stored inside, how damp, etc. I realise that even if I can find the power consumption of the motor when running there are still unknowns to consider, but at least I have something I can monitor fairly easily.


Typical figures I see quoted for energy are around 350 kWh per year. This is equivalent to an average power consumption of 40 W. Clearly my old fridge-freezer is consuming well over double this figure. The message is becoming clear, then, even if the analysis is blurred - I need to replace that fridge-freezer soon. It will probably save its cost in about four years.


I submit this post with an interest to find what others think about the way fridges are sold and how we are supposed to assess energy usage. Different manufacturers seem to present much the same marketing information. Does anyone know of any industry standard affecting the way this information is given?
  • 0

    Denis McMahon:




    mapj1:

    . . .

    Also, site your fridge in a place where it can be easily cooled - it would be possible to make a fridge where the waste heat went to heat the washing up water, but as far as I know, no-one does, but at leat make it have an easy life.

    . . .

     




     

    Our fridges are in an unheated utility room, several degrees cooler than the kitchen in winter, so we are giving them an easy life as practicable.

     




    Wrong,  you are not giving them an easy life as they are made to work in a heated room.


    You actually need to buy an Outdoor fridge and freezer to use in an unheated room or outbuilding.


    Andy Betteridge 

  • 0
    If you read that link Beko say you may only be able to use the freezer box in a fridge freezer in a garage or outbuilding as the fridge section may be unusable. 


    Andy Betteridge
  • 0
    It's generally only combined fridge/freezers that have a problem when kept in a cold room.  In the interests of cheapness, the manufacturers often only put a thermostat in the fridge, and use the same compressor for both.  If the ambient temperature is below 5 degrees, then the fridge never turns on.  So the freezer never turns on.  So everything defrosts.


    So long as there's no damp, you shouldn't have any problem with separate fridges or freezers.
  • 0
    One for a Saturday morning. Warming the fridge up makes the freezer work better in a fridge freezer.

    YouTube video


    Andy B
  • 0

    Roy Bowdler:
    Many years ago, we went on a winter holiday leaving the house central heating on a minimum setting to prevent freezing. On our return the freezer compartment of our Fridge-Freezer had defrosted.  A relative had a chest freezer in an unheated garage which never seemed to have that problem.  I came to the conclusion that my Fridge Freezer had been operating in conditions significantly below its recommended ambient temperature range. Has anyone considered this issue?

     




     

    Thanks Roy. I note there have been some other posts also mentioning this issue; thanks for your thoughts, everyone.


    I have noted in my investigations that fridge manufacturers in their specifications usually define a minimum environment temperature. It is therefore prudent to check this detail when on considers a purchase, to make sure the refrigerator is suitable for its intended environment.


    A chest-type freezer is more likely to be used in a garage therefore it will more probably be designed to work in a cold environment, below freezing point.


    Regarding fridge freezers with single "works", the theory that it is regulated by a single thermostat in the fridge section rather than the freezer - hence the freezer stops working if the fridge part is cold enough - seems plausible. I am not keen on these; I once managed to "fix" one for a friend (not quite sure how) but I was generally put off and felt they were less reliable.


    Our fridge freezer has separate compressor units for fridge and freezer. I am quite satisfied that it is OK in its present environment; the motor is notably less busy, and smart meter indicates lower consumption, now that summer is over and we are well into autumn. I don't know what would happen if I put it in a freezing garage but I have no intention to do so. I have no manufacturer's note of minimum environment temperature.


    I am sure there are other theories we could apply to this. I'm no refrigeration specialist, but I could take a guess that if the condensate is over-cooled, it may not evaporate when it reaches the evaporator and the whole cycle could stall. Are there any refrigeration engineers out there, who could throw some light on this?
  • 0

    Simon Barker:

    It's generally only combined fridge/freezers that have a problem when kept in a cold room.  In the interests of cheapness, the manufacturers often only put a thermostat in the fridge, and use the same compressor for both.  If the ambient temperature is below 5 degrees, then the fridge never turns on.  So the freezer never turns on.  So everything defrosts.


    So long as there's no damp, you shouldn't have any problem with separate fridges or freezers.



     

     

    Yes but:

     

    If you read that link Beko say you may only be able to use the freezer box in a fridge freezer in a garage or outbuilding as the fridge section may be unusable. 


    Andy Betteridge 



    My emboldening. Thanks for your thoughts, gentlemen, but there seems to be a bit of contradiction here. Hence this subject is worth further investigation.

  • 0
    There’s the theory that when setting up a new freezer or fridge that you should leave it it to stand for twenty hour hours to let the gas “settle”.


    I have asked both commercial and domestic fridge/ freezer engineers about this, they both said the same thing that as soon as they have replaced or topped up the gas the appliance is turned back on and they have never experienced any problems.


    Andy B.
  • 0

    Denis McMahon:




    Simon Barker:

    It's generally only combined fridge/freezers that have a problem when kept in a cold room.  In the interests of cheapness, the manufacturers often only put a thermostat in the fridge, and use the same compressor for both.  If the ambient temperature is below 5 degrees, then the fridge never turns on.  So the freezer never turns on.  So everything defrosts.


    So long as there's no damp, you shouldn't have any problem with separate fridges or freezers.



     

     

    Yes but:

     

    If you read that link Beko say you may only be able to use the freezer box in a fridge freezer in a garage or outbuilding as the fridge section may be unusable. 


    Andy Betteridge 



    My emboldening. Thanks for your thoughts, gentlemen, but there seems to be a bit of contradiction here. Hence this subject is worth further investigation.

     

     





    A cut and paste from the link above:

     

    Outdoor Fridge Freezers For Garages & Outbuildings



    You don’t need to worry about where to place your fridge freezer with our Freezer Guard technology. Even if temperatures drop to as low as -15°C, you can rest assured the freezer compartment will always function properly to keep your frozen food frozen – perfect for when you need to place your fridge freezer in your garage or outbuilding.



    We recommend you only use the freezer compartment in low ambient temperatures and not the fridge compartment.


  • 0

    Denis McMahon:




    Simon Barker:

    It's generally only combined fridge/freezers that have a problem when kept in a cold room.  In the interests of cheapness, the manufacturers often only put a thermostat in the fridge, and use the same compressor for both.  If the ambient temperature is below 5 degrees, then the fridge never turns on.  So the freezer never turns on.  So everything defrosts.


    So long as there's no damp, you shouldn't have any problem with separate fridges or freezers.



     

     

    Yes but:

     

    If you read that link Beko say you may only be able to use the freezer box in a fridge freezer in a garage or outbuilding as the fridge section may be unusable. 


    Andy Betteridge 



    My emboldening. Thanks for your thoughts, gentlemen, but there seems to be a bit of contradiction here. Hence this subject is worth further investigation.

     

     




     

    I see no contradiction.  A normal domestic fridge/freezer isn't designed to be used in a cold room.  The Beko one linked to is intended for cold locations.  Their comment on the fridge is presumably warning that a fridge won't be any use below 0°C.  Because at that temperature, everything in the fridge would eventually freeze solid.
  • 0

    Legh Richardson:


    . . .


    After all my continual opposition to smart meters my partner has signed us up to a fixed rate energy package which includes gas, electricity, broadband, mobile phone and a smart meter. I'll now be able to check my freezers for energy consumption...what fun!


    Legh

     



     

    I too was once sceptical about whether smart meters could assist with saving energy. Like many people, I thought that energy saving was just applied common sense. Don't heat unused rooms; don't over-fill kettles; don't simmer pans on the hob faster than necessary, do use low-energy lamp[s, etc.


    Then an incident made me think again. We have in our kitchen an oil-filled electric convector heater, sometimes used on cold mornings to give extra heat below the breakfast table. Despite precautions to ensure it was not left on accidentally, this once happened and it was left on for 10 days before it was noticed. That's 900 watts continuously over 10 days. I decided that a smart meter would have spotted that.


    The smart meter we now have has already enabled me to make many useful observations that I would not have thought of. In due course it should assist with the new tariffs we will inevitably have as daily energy usage profiles change.


    As for that convector heater, the smart meter has indicated that it consumes 900 W only when it warms up. Once up to temperature its consumption switches between 450 W and zero. Clearly some thermostatic action within, which I was not aware of.

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