system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: If most electronic appliances' efficiency losses are through heat, does that mean that electric heaters are 100% efficient?

Edit:

Many thanks for your input everyone!

Just to clarify, I don't want to take into account the method of generating electricity or shipping it to the home, or the relative costs of gas and electricity. I just want to look at the heater itself! i.e. does 1500W of input into a heater produce 1500W of heat, for example? Or are there other losses I haven't thought of. Heat pumps are off-topic.
gpt
Yes, electric heaters convert 100% of the power that they consume into heat. So they have an efficiency of 100%.

Heat pumps move heat from one area (outside your house) to another area (inside your house) The amount of heat they move is typically about 3 times more than the power they consume. So the in terms of energy-to-heat efficiency, they are 300%+ efficient.

But thermodynamically they are not “creating” heat from nothing. So heat pumps are not perpetual motion machines, they don’t break any of the laws of thermodynamics.