How can you tell if something is energy efficient based on watts and volts?

Question

I live in a van and have only a certain amount of energy I can use each day but can never tell what appliances are efficient or not. HELP

In: 1

Answer 1

You can’t, really? How many watts an appliance uses doesn’t tell you how efficiently it’s using it. Something like an electric heater is near enough 100% efficient because every watt it consumes is converted to heat, which is obviously the whole point of such a thing, but it will use a lot of power doing so.