James wrote:
The A, B, ... relates to the product.
The most efficient fridge will use much less energy than the most
efficient
large dehumidifier, for example.

Ideally, you want a Kwh/cycle, or Kwh/year figure from the makers.

Does it relate to the product? or just a category for kwh/cycle/year?

i.e is there such a thing as a A rated tumble dryer?

Well, one example might be one that used a heat pump to generate the
heat needed to dry the clothes, and condense the water.