Why is frost bad for a freezer?

Dave - The problem is, because it's a good insulator. The way a freezer works, you have a load of pipes at the back, you compress a gas in the pump, that makes it hot and loses the heat out of the back of the fridge or freezer. It then pipes this condensed, compressed room temperature gas into the freezer, it then expands, evaporates, gets cold, and so the coldest bits of the fridge are where this expanded gas is flowing through. The problem is that wants to get the heat from the fridge, but if you've got a great big layer of ice, that's going to insulate the cooling part of the fridge from the contents of your fridge, so the fridge is going to be warmer, which means that the actual fridge-freezer is going to work harder to keep cold, which means it gets even colder, it means you get more ice that will build up so it'll go horribly wrong until the fridge just conks out.

Chris - And you have a big bill.