Yes, its true what they say about Chest Freezers

Save 90% of the energy
Page Three girl Keeley Hazell has been campaigning for houses to switch to energy-saving Chest freezers. We thought it was just an urban legend, but Keely is right. For years there has been a persistent rumour that chest freezers can be used as fridges at just one tenth of the power consumption.  A stream of stories on Australian web sites seems to confirm it.

The theory is that a chest freezer will use less power because the horizontal lid doesn’t let cold air fall out when it’s opened, and it has very thick insulation compared to a fridge. People are claiming some amazing power consumption figures, but would it really work that well?

Australia is currently hosting the worst drought in the world so there are few better places to test the theory.

Darren from Green-change.com in Sydney tested his old fridge with a MS5116 mains power meter, only to learn that it was using 2.5 kWh of electricity per day. His total household energy consumption at the time was around 20 kWh per day, so the fridge was responsible for 1/8th of that!

He bought a 210 Litre chest freezer for $90 second-hand, and ordered a FridgeMate MkII digital temperature controller online for $50. The temperature sensor needs to sit somewhere inside your freezer but not touching the walls.

It can cut the power when the temperature drops below a set point

Once it was loaded up and stabilised, Darren left the MS6115 on the chest fridge for 24 hours. “When I came back, it was reading a cumulative usage of just 0.2 kWh! Given the limited 1-decimal-place reading, I’m calling that 0.2-0.3 kWh. Not bad at all – it’s around 1/10th of the old fridge.”

That means you could power it from a single solar panel – something that was previuously considered inpossible for a fridge.

12 Responses

  1. USA 120v been researching this physically looking at freezers as well as the 5 cf i own now 134a 1996 model. it is rated 6 amp 120v. a 7.2 in the store has a rating .9 amp 120 v . so significant difference in consumption and that was not listed as energy star. the current side by side refrigerator is 10 yrs old 6.5 amp have not checked new fridge rates. only thing i have found some not all of the new freezers have much narrower temp ratings where there used older ones could run 0 to 110 f i read specs on one 55 to 90 f temp so garage or back porch is no longer safe others have better ranges but something replacing an old one
    so research is key. as for the opening the upright sucks the air out of the whole ref or freezer opens and continues as long as open when door where chest cold sinks stays in box

  2. Great… I have gained an additional information about the chest freezer. I would be recommending others to prefer low power consuming objects to save electricity and am sure that chest freezer is also one of the objects that consume less power. Thank you for sharing your views.

  3. – so unless you leave the fridge door open for extended periods of time, or open and close it many times per day, there won’t be that much difference.

    Which is what most people do.

  4. Sorry… have to burst this bubble a little.
    Looking at the data alone, we’re comparing old technology to new. A chest freezer built today will have a heat pump that is far better than the one in the old fridge.
    Next, insulation. Freezer insulation is designed for a greater thermal differential. Here, we have a new freezer versus an old fridge – again 2 different technologies, insulation and design factors. A new fridge v an old fridge would have similar differences in insulation as we pay a premium for energy efficiency as a feature now.
    Last is the upright v chest design. Here, there is a big difference – but this difference is only valid when opening and closing the fridge and is dependent on the thermal heat capacity of air – which is very low – so unless you leave the fridge door open for extended periods of time, or open and close it many times per day, there won’t be that much difference.
    To illustrate this, say we were to replace the old fridge with a A++ rated (European rating) 90W 220l freezer that has a 90W power rating and needs to be switched on for 1 hour/day to maintain a 5 C temperature – you’d have the same effect. By comparison, there is a fridge of the same exterior size, with less insulation inside with a 90W compressor which does pretty much the same task.
    The differences here are that to cool down to -12C, you waste more energy as the efficiency of the heat pump/compressor drops as the temperature differential increases.
    In conclusion – the increased insulation that a freezer has would indeed assist with losses but that is a trade-off between exterior size and internal volume (Hence a much larger appliance cost for the same internal volume) any other differences would be minimal in a responsible usage scenario.

    1. My 1 year old upright freezer (part of fridge freezer compbo) with it A++ rating starts to thaw hours before my 22 year-old chest freezer when the power dies for extended periods. Not sure about power required to get it to required temperature, but insulation far superior on the chest.

  5. The power consumption claim of 0.2 kwh in 24 hours is very achievable. I am currently using a chest freezer as a refrigerator and have measured similar power consumption. Instead of using a timer to control the compressor I hooked up a new thermostat and relay switch so that the unti holds a temperature of 4 degrees celsius. You could figure out a time interval for the compressor that would get you a fairly consistent temperature I suppose as suggested in an earlier comment and this would be a bit easier to set up but I wanted a system I could always trust even as my house temperature changes. I have posted the details of my modifications here: https://practicallyoffthegrid.com/2010/02/how-to-make-your-own-high-efficiency-refrigerator/
    The changes are pretty straight forward and cheap! This is a great way to take a huge chunk out of your energy consumption so your energy generation requirements for off-grid living can be lowered substantially.

  6. Is it possible to turn a chest freezer into half freezer, half refrigerator?

    If so, which would be the best way to divide it — side by side split or horizontal split?

    I just see regular refrigerator-freezers as so inefficient because anytime you open the door you lose a good deal of cold air, and forget getting anything out during a power outage (sigh).

  7. I have been using a 270lt chest freezer as my fridge for about 10 years now. All of my power comes from a small solar system with a small 240V sine wave inverter. I have made no conversion to the chest freezer and don’t use a temperature controller; all I have is a $5 wall timer which can be set to turn on in any 15min intervals during the day. Usually in the summer months I have it set to turn on the fridge (formerly known as freezer) at 15min and 30min intervals for a total of 3hr. In the cooler months its probably more like 2hrs total but I rarely get too pedantic about it because it is so low. The compressor motor will always run during these intervals as the fridge is always below the nominal freezer temperatures and so the freezer thermostat never functions. It may sound a little crude but the temperature in the fridge does not vary a great deal, I have monitored this. The beauty of this system is that you can control when you use energy to cool the fridge and how much which is beneficial on a small solar system. I run the compressor sufficiently during the sunny hours to cool the fridge down so that during the night I rarely ever have the compressor set to run and it stays cold all through the night. This makes a huge difference to your storage battery requirements and effectively you are using your fridge itself to store energy harvested in the daytime. I have never had any spoiled food and weaned myself off the pleasures of frozen treats many many years ago. I am also a vegetarian and so I don’t have a need to have frozen animals in a freezer.
    The chest freezers are certainly better insulated but importantly they also have the condenser tubes wrapped all around the outside of the cabinet so there is not the problem of condensation and the need for mullion heaters as found in conventional fridge/freezers as heat is dissipated all over the cabinet.
    The only drawback might be the convenience of access and the ease of cleaning and draining accumulated water at the bottom which you might have to do every few months.

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