Popular Misconceptions

I’ve had a request from a reader to look into what could turn out to be a popular misconception. The question that they put to me was whether it is really true, as some people believe, that fridges and freezers are ‘more energy efficient’ when full?

I guess, in part, this comes down to what is meant by ‘energy efficient’, but the crux of the issue is whether it’s true that a full fridge or freezer uses more electricity than one pretty much empty. If so, this would seem to be counter intuitive (which is probably why the notion has spread, it has the ’surprising’ factor). After all, you’d reason, it takes longer to boil a full kettle than a one-cup-full kettle, and longer to freeze a big joint of meat than a tray of small ice cubes.

I can see some possible truth in the idea that a full freezer will, once cooled to the temperature on the thermostat, be less prone to suddenly warming up when you open the door than an empty freezer. But this is surely simply because opening a freezer door exposes it to a certain amount of heat, and with a full freezer this heat will be spread out amongst a bigger surface area of frozen foods. It must still have taken more energy in the first place to freezer the larger amount of food.

If my science is completely off, let me know.

Energy efficiency is a complicated issue (probably), and whilst I want to keep this blog on-topic to the discussion of popular misconceptions, it’d be good to get to the bottom of this question.

A related topic that I’ll return to in the future, which I also suspect could be a popular misconception, is the amount of electricity that appliances uses when on standby. Because I’ve heard people claim that it can be as high as 90% of the amount used when on full power, which can’t possibly be true, surely?