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Freezer power saving overnight.

hertzal123
Just read on another forum about a device that switches off domestic freezers for short periods overnight to save

power.Just wondered if this is worthwhile in a domestic setting.

                                                                                    Regards,

                                                                                                   Hz
  • 0
    Sounds like snake oil to me.

    Freezers are controlled thermostatically. If the supply is turned off when the thermostat has already turned off the compressor, then utterly pointless. If this external device turns of the supply when the compressor is running, then on restoration of the supply, the compressor will run for longer to "make up for lost times" and no saving will result.

    If the supply is turned for several hours, then a slight saving will result, but only by raising the average temperature within the freezer. This might have serious implications for food safety. If you consider a slightly less cold storage temperature IS acceptable, then simply set the existing thermostatic control to a slightly less cold setting.


    If an off peak tariff is available, then a slight money saving may be achieved by turning off a freezer for say the last hour or the last two hours of the full price hours. The freezer will then run for longer during the off peak hours. So doing wont save ENERGY but will save MONEY by transferring a little of energy use into the off peak hours.
  • 0
    Normally the thermostat does that for you.There are devices that reduce the drive to the compressor motor once it is up to speed (by measuring the back EMF to deduce the motor is running, and then slicing the cycles like a thyristor lamp dimmer) 'savawatt' was one model, but I have not seen one for years. I suspect modern fridges may include something a bit like this anyway
  • 0
    I don’t think the domestic version is made anymore.
  • 0
    Thanks for the replies,did,nt think the device would work myself.

                                                                                         Regards,Hz
  • 0
    I agree.

    However I have an elderly (35 years old) but apparently perfectly good chest freezer.

    All the advice I get is that they will not be as efficient as a new one would be and that I should change it. However, before I do, I would like to know if I can find out how much a chest freezer of a certain size should consume in a day (assuming it is not opened) for a given ambient air temperature. Then I could measure the consumption of mine and see if it is really in need of being changed.

    Anyone know if this data is available?
  • 0
    A newer appliance will probably use less energy.

    The energy consumption of a proposed new appliance can be found on the energy label attached to the appliance. Expressed in terms of number of KWH used per year.


    The energy consumption of your existing freezer may be measured by means of a plug in power and energy monitor these are available cheaply on line.

    Alternatively use a spare DNO type electricity meter, many people in the electrical industry have one lying around.


    No great accuracy can be expected since the test conditions for the new appliance may differ from the actual conditions under which the existing appliance is used. Ambient temperature and frequency of opening are the main factors.
  • 0
    Harry Macdonald:

    I agree.

    However I have an elderly (35 years old) but apparently perfectly good chest freezer.

    All the advice I get is that they will not be as efficient as a new one would be and that I should change it. However, before I do, I would like to know if I can find out how much a chest freezer of a certain size should consume in a day (assuming it is not opened) for a given ambient air temperature. Then I could measure the consumption of mine and see if it is really in need of being changed.

    Anyone know if this data is available?


    The insulation might not be as good. You could supplement it with a few slabs of cellotex duct-taped to the sides and top, leaving gaps for controls, vents etc. 

    Just a thought.


  • 0
    Harry Macdonald:

    I agree.

    However I have an elderly (35 years old) but apparently perfectly good chest freezer.

    All the advice I get is that they will not be as efficient as a new one would be and that I should change it. However, before I do, I would like to know if I can find out how much a chest freezer of a certain size should consume in a day (assuming it is not opened) for a given ambient air temperature. Then I could measure the consumption of mine and see if it is really in need of being changed.

    Anyone know if this data is available?


    Our latest fridge-freezer is bigger on the outside and smaller on the inside than the previous one - that gives you an idea how much insulation has been added.


    I wouldn't be at all surprised if your aged freezer is costing £200 per year to run. I find it difficult to see how that sort of money can ever be recouped.


  • 0
    Good thought about the cellotex - except that it doesn't have any fins at the back but uses the skin of the freezer to dissipate the heat!

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