Refrigeration using solar power

Refrigeration using solar power is a breeze for even a small inverter.

Modern fridges and freezers use relatively little power; somewhere around 300W depending on the size obviously. The total energy consumption is likely to be less than 2 kilowatt-hours per day.

Solar lens effect

This page was last updated by Bernard Preston on 9th January, 2024.

Since most of this energy is required during the day when it's hot, there is a perfect synergy with solar-power. 

My first inverter was rated at 2kW and being a novice I was astonished that it would power a fridge and separate freezer when the grid in our area collapsed for 36-hours; they were full of goodies just before Christmas.

Even if you plan to go off the grid which I do not recommend incidentally, adequate lithium batteries will handle the cooling at night with relative ease except perhaps in a very hot climate.

Using prepaid electricity is a better option.

Often the decision to toss an old-fridge or freezer will not be because it no longer functions; but since the seals started to deteriorate it has begun to run all day consuming large amounts of electricity. The compressors usually last for years before they fail.

Instead of tossing that old fridge, put it rather in the garage and run it only on solar power during the day. Keep items in it that need to be cool but it matters not if they warm a little during the night; cold-drinks and beers, for example.

Going off the grid

We have had second thoughts about our aversion to going off the grid since a power-surge from the utility caused immense damage down our street. The figure shown on the multimeter below is double the normal voltage; 220V in South Africa.

Power surge producing 431 V instead of 220 V is giving us thoughts of using solar power exclusively.

Refrigeration using solar power

Refrigeration using solar power is very efficient as cooling is needed mostly during the day.

This is particularly true for green-freaks who have a lot of stored organic foodstuffs. For example, we purchase five 50kg bags of wheat berries every year from a farmer for baking our own wholemeal bread. They need to be frozen for two weeks to kill the weevils.

You'll never find them in white flour by the way; the weevils know the difference between junk food and the real McCoy. Wheat-berries have many of the goodies that we need for vitamins, minerals and phytosterols such as lignans. They are typically extracted during the refining process and sold to pig farmers. We are left with the empty calories.

Then it's always useful to have a couple of extra ice-trays should friends and family suddenly descend on you unexpectedly.

We also keep our tahini in the fridge; it's easier to purchase half a dozen bottles at a time because you have to find a Greek or Lebanese shop. It is good stuff by the way and much nicer than peanut-butter to my mind. We use it for making our quick hummus that turns even the dullest salad into a delight.

Then because I'm the bar-wench at the gliding club, all the surplus drinks are kept in that outside refrigerator in readiness for next Saturday.

In short refrigeration using solar power is a breeze for your inverter if you have enough PV panels; and air-conditioning too. It reduces the payback time of your setup and we find it very useful having a second old freezer that costs nothing to run during the day.

"Shoprite is currently in 2023 spending an extra R100m per month on diesel to keep the lights on and the food chilled in its stores."

On the subject of inverters and PV panels, don't make the mistake I made by putting in a Mickey-Mouse system. It does little for the environment if you produce only 2kWh of sunshine energy per day; and it will stress you out.

My strong advice is to go straight to at least a 60-amp regulator and 5kW inverter; using a 48V system. You will be upgrading to this eventually so do it right from the beginning; then it hurts only once.

You can add more PV panels later; and extra-batteries should you want them but to upgrade the inverter and regulator after a year is a serious waste of time and money. Do it right from the start.

A 48V regulator is so much more efficient. Higher-voltage means lower amperage with fewer lost watts in the cabling; you can use thinner wires too, saving you on the setup costs.

If you are serious about going solar and you have the money, then go straight to a 10kW inverter; that's what I now have and we can run the dishwasher, the oven and charge the E-car without a problem during the day.

It's such a pleasure using only $5 of electricity per month from the utility; payback time is five to ten years. The best is pure sinewave energy with no dips and surges to burn your electronics.

The best regulator incidentally is called a solar charge controller MPPT; it extracts about a third more from the panels. It costs around an extra eighty bucks; in the long term it's definitely worth it.

But stay on the grid for the inclement weather.


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Inverter technology

When purchasing units requiring refrigeration with solar power, it's worth spending the extra and getting one that uses inverter-technology.

There are three reasons that I can think of.

  1. Inverter fridges and air-conditioning units use about 30% less electricity.
  2. Normal electric-motors require a heavy current to start up; that means you need a much larger inverter.
  3. They are much quieter.

Fridges using inverter technology have variable-speed motors; that means if there is a small rise in temperature, the compressor doesn't need to work at peak capacity, saving electricity.

The compressor never switches off but runs at a very low-speed, making far less noise.

Freezing chickpeas

Freezing chickpeas is the solution if you enjoy hummus; there are several distinct advantages over using the canned variety. Pressure-cook your dried legumes and store the excess with refrigeration using solar-power.

It makes sense to pressure-cook a large amount, say a couple of pounds; and then drain, cool and freeze them in small packets.

I like to use recycled food grade plastic packets incidentally; our world will soon be suffocated by non-biodegradable synthetics.

Then freezing chickpeas is a breeze; even more so if you have refrigeration using solar power.

They're known as garbanzo-beans, by the way in some parts of the world.

I am sure you have noticed the commitment to permaculture here. Using a pressure-cooker saves time, energy and money. By freezing chickpeas it reduces our dependence on cans. Recycling plastic packets is protecting the environment; and Mr Golden Sun provides the power to boil and chill the garbanzo beans. Hummus is one of the world's most nutritious foods.

Wean off plastic if you want your grandchildren to have a habitable world. Capturing solar power energy is another very significant step in protecting our environment; if Bernard Preston can do it, so could you.

Then you can run all your appliances like refrigeration using solar-power.

Using frozen chickpeas it takes me only five minutes to throw together our authentic hummus recipe; you will need to find a source of tahini. It will turn even the most boring salad into a delight for the tongue; and happiness for the colon.

If you want to avoid colorectal tumours make sure you are enjoying organic green food every single day.

Low GI bread

Bread machine loaf baked using solar power is dependent on refrigeration to keep the wheat berries from bugs and moisture.

Low GI bread too can be cooked using a bread-machine powered by solar; I alluded above to the fact that we store wheat berries for a whole year by refrigeration using solar power.

Including grinding the wheat to make healthy flour, it takes only five minutes to prepare the goodies for low GI bread. No chemicals, half the salt and a wonderful mixture of ground seeds give this loaf a divine flavour.

Bake and cook during the day when the sun's energy is pouring in; and refrigeration using solar power has so many applications in the home.


Tahini is a wonderful paste made from sesame. Like all nuts and seeds, once the shell is cracked it starts to go rancid very quickly; our solution is refrigeration using solar power.

Nuts should be eaten freshly-cracked, or vacuum packed and seeds kept cold; refrigeration using solar power is perfect for keeping goodies like these cool.

This tahini paste can be found in Greek and Lebanese shops; we enjoy it too on our low GI bread to mop up salad juices. The taste is heavenly.

Tahini and the benefits of freezing chickpeas is one of the many discoveries Bernard Preston made whilst living in the Netherlands for seven years. Have you read Stones in my Clog?

Holland is also where he got the inspiration for using solar power. Refrigeration is just one of the many blessings brought by Mr Golden Sun, as his grandchildren call him.

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Bernard Preston

Bernard Preston is a physics major who continued his studies after teaching high school science for nearly a decade to become a DC. After forty years in practice he is now semi-retired; pottering in his organic garden, playing with his solar generator and flying gliders over the weekend; refrigeration using the sun's energy is just one small benefit of going green. 

Live life at full-speed is his motto, foot flat on the accelerator and hope to drop dead in harness with all your marbles intact. No old age home and dementia for him.

Refrigeration using solar power is just one of his little interests. An air-conditioner energised during the day by the sun is his next chore.

He's something of a green freak with organically-grown fresh vegetables, huge compost heaps and worm farms; with free ranging hens that are all part of their green home.

Then he's a writer of some note; you might enjoy one of his books from the coalface, like "Bats in my Belfry." He is busy with his seventh; called Priests Denied, it is going to be controversial.

See the navigation bar above; they are dirt cheap on Kindle.

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56 Groenekloof Rd,

Hilton, KZN

South Africa