PowerSwitch

Hi,

Any ideas of the cheapest way to run fridges and freezers?

* Make them 'less cold'?
* Add insulation to the top, sides and door?
* Run for say just 50% of the day?
* Fill any spaces with water bottles to act as (cold) thermal stores?

Make them less cold, will undoubtedly reduce energy used but will also reduce the safe life of foods stored therein.

Extra insulation can help, but before doing this make certain that the condenser is not built into the case. Damp followed by rust is a risk under the external insulation.

Turning off for part of the day wont help, unless on an off peak tarif when it can transfer some of consumption from peak to off peak.

Keeping it well filled saves losses when opening the door, but otherwise makes little difference.

The biggest savings are from

Buying a high efficiency appliance initially.
Keeping it defrosted.
Keeping the condenser clean.
Placing it in a cool area, but not too cold in the case of combined fridge freezers.
Minimising door opening.

adam2 wrote: ↑22 Aug 2022, 12:48 Placing it in a cool area, but not too cold in the case of combined fridge freezers.

I moved into a house with a fitted kitchen.
Fridge/freezer positioned directly next to the oven....
That can't be good, but will need to wait for a new kitchen before it can be rectified....

adam2 wrote: ↑22 Aug 2022, 12:48 Turning off for part of the day wont help, unless on an off peak tarif when it can transfer some of consumption from peak to off peak.

Through the winter we have our chest freezer and fridge on a timer so they are off for approx 6 hours from 1am to 7am. This limits their demand from the battery, shifting it to when the sun is (at least potentially) shining. We're off-grid, 100% PV though.

I've been wondering about the efficiency of freezers too. I think it would be advisable to remove the metal outer skin where possible, then apply the extra insulation, otherwise the metal sheet will provide a circuit for external heat to bypass the extra insulation. My plan would to be to add 100mm or so of polyurethane / pentane insulation board ( "Kingspan" ) to all except the radiating coils, then box with 12mm plywood. Status lights can be extended and installed on the new outer surface - I'd be wary about leaving them on under the new insulation.

As well as improving insulation you can convert a chest freezer into a fridge by changing the thermostat being that cold air will no longer 'fall out' of the opened door of a chest 'fridge' like in an upright one. Use/locate in a cold room or have a cold air supply to the heat exchanger and use the heated air for something useful. Use some basic knowledge of physics. Open the door less. Defrost items in the fridge first and not in the microwave. In America I have seen on the internet some cupboards put against the outside walls where cold air from outside is allowed to cool the cupboard and make a virtual fridge.

Maybe make an icehouse as well.

I have heard that the Japanese made a totally 'no-moving-parts' mechanical fridge that used ether as a coolant that got cooled on a radiator/condenser that was exposed to the night sky and was then closed off during the daytime.

The more modern trends of both putting the condenser in the sides rather than at the back , and the blastedly integrated kitchens don't help, neither does putting them next to any heat source or heaven forbid a hot conservatory.

If possible creating an air channel for cool air to flow over the compressor and condenser and the hot air to be removed help, a temperature controlled fan/s can be used, but that is much easier to do if the supply voltage is 12/24 DC (its not hard to do if its 230V AC , but you need to know what you are doing).

As noted by britdownunder using a chest fridge or a converted chest freezer will (all else being equal) be more efficient , but can be more of a pain if you
are regularly using part opened/used containers or plates/bowls with cling film over them.

Also remember you get what you pay for. We bought a VERY expensive Liebherr freezer some years ago and it's been trouble free. It claimed to be able to keep frozen food safe for over a week of no power and I can believe it. The walls, floor and lid are over 12 cms thick.

Even after a day-long power cut once, when power returned the internal temperature had not gone up one bit. Mind you, it was chocca with peas, broad beans and green beans from the garden, so that helped.

Just a couple of thoughts;
- We've used large Coleman cool boxes on camp before, which are very well insulated. Could electricity costs get to the point where it would be cheaper to buy packs of ice from the supermarket periodically and just use the cool box?
- Putting frozen items in the fridge to slowly defrost should reduce the time the fridge compressor runs.

I would not expect any saving from use of purchased ice and an insulated box. It takes energy to produce the ice, and probably at a higher rate per unit than is paid domestically. The seller of the ice probably makes a profit.

Defrosting frozen foods in the fridge does save energy, not that much but every little helps.