It is meant to give 'continuously varying' (rather than on/off) control of the compressor, which allegedly has a benefit in terms of electricity consumption (and, some say, noise). If you Google 'inverter fridge' or 'inverter freezer', you'll get countless hits - the first (very brief) one I found was ...
click here .
Kind Regards, John
Not quite 25% to 100% once 25% is reaches it turns off but it would seem although that is how large commercial freezers work it is not what the inverter does with domestic freezers.
If we look at a cooling fan in a computer it is inverter controlled the tiny inverter inside the fan makes three phase power to drive the squirrel cage motor this removes the need of brushes.
It would seem the domestic fridge and freezer use inverter control in a similar way as being more reliable than capacitor start but motor speed stays the same and the temperature is still controlled by the mark/space ratio.
How ever I can't find any data to confirm this except my inverter controlled fridge/freezer motor sound does not vary in sound as would be expected if running 25 - 100% of full speed to adjust the cooling required and it does seem to switch on and off.
I would agree about miss information after reading how you should change ones old fridge freezer to save power I decided to do the sums myself. I did not include interest on the money used to buy a replacement but at £450 pound for new fridge/freezer which uses half the power of the old one it would take 11 years to pay for the change.
As we look at cheaper models which are not frost free the time for it to pay for it's self clearly reduces but fitting a Christmas Turkey in a non frost free model is a problem and also the figures don't include the cost of de-frosting.
With my mother I do a major shop and fill both her fridge/freezer and small freezer on top of main fridge/freezer and the care workers move the food down as required. Once empty it is switched off and allowed to de-frost until next shop. So with her freezer de-frosting does not cost anything. But for me to de-frost the freezer means removing all food and storing in bags then direct a fan into the freezers open door to rapidly de-frost after which all the food is replaced and this means de-frosting clearly costs money.
So to compare too freezers we have to also consider the biggest item which can be stored in it and maintenance costs like de-frosting and also the big question how long will it last and when it fails what will be the cost of the food lost. Clearly much of this is unknown.
But to replace a non frost free freezer at around £150 one may break even at 3 years but as we move to frost free at £300 to £1000 then the time to break even is far longer. And as we reach 20 years to break even then also we have to consider the interest which would need paying to get the replacement and we start to reach infinity years.
Because we never turn our freezer off we are told on the energy web sites this is a major energy saving thing so if the major one does not show saving by replacing then it would seem unlikely any of the other items we are encouraged to change will save us money either.
Having said that in last two months I have needed to replace both fridge/freezer and freezer. The freezer was going to cost in excess of £200 to repair and at £330 for new one it just did not make sense to repair. The fridge/freezer is still working but has both a thermal insulation fault which means food may not be kept at -18 and +4 degrees C and also an electronic control fault which means it is likely to fail in near future so in both cases for me there was no option but replace.
However my wife and I have been at loggerheads over the unit to purchase as a replacement. The major point was frost free v non frost free and she won in the end and we got a frost free.
But this also caused problems as the cheap frost free option was a Beko and it was an "A+" version of the "A" freezer which had failed after only 6 years so I was not happy getting another freezer the same as the last. Settled for a ex-demo freezer.
The fridge/freezer was also a battle and in hind sight we made a mistake but at the time we did not expect the freezer to fail just two months latter. Original was 50/50 split new one was 60/40 split with a bigger fridge and we also lost the cold water feature. Old hoover was plumbed in giving a continuous cool water feed without any huge tank which needed filling.
It would seem it's all these little things which are more important to the female does it make ice cubes and does it have cold water and does it have special area to keep ice cream which is not quite as cold as rest of freezer and have special draw for fast freeze.
All these points and having ability to set the temperature by 1 degree C from -14 to -24 or simply high medium low seem to be more important than I had considered. I thought all freezers were -18°C and all fridges with +4°C shows how much I knew.
On getting the fridge/freezer I noted solenoids to work fridge and freezer and thought the inverter control was to allow different pump output depending if one or two solenoids were open. However on getting the freezer (same make) this also had inverter control so it would seem I had got it wrong. The new freezer as yet has not worked on plugging in it did not work. There was no other freezer my wife liked so it was agreed to allow a repair. The guy arrived and said the main control panel had failed and trying to impress I say "Oh is that the inverter" the answer was a surprise as he said the inverter was built into the motor. Hence the question.
So at the moment the old fridge/freezer which I had kept with the idea I may use it for my home brew beer has been pressed back into service. I hope Monday all food will be transferred and old unit switched off again.
This has however allowed me to use an energy meter on the old condemned fridge/freezer and see how much power it uses. Remember this has a known thermal insulation fault. At 560 kWh/annum it is rather poor compared with new fridge/freezer at 277 kWh/annum but even so it will take 9 years before we break even. Since I think total failure is just around the corner I am happy to replace is right move. But had not the fridge/freezer repair man pointed out the thermal insulation failure and the insurance paid out as a result I would not have changed it.
I even wrote a java script web page to work out the savings of changing to a modern A+ fridge/freezer but never uploaded it once I realised in the main it showed buying a new fridge/freezer purely for economy reasons just did not work.
), I am rather sceptical as to whether what eric said is correct (particularly given the small amount of space in which to 'hide' an inverter in many of these fans) - at least for 'run-of-the-mill computer fans !! - but I am frequently wrong 
