No it's same thing. All energy eventually becomes heat and there can be no lost energy in a system. In the case of a GPU we're converting electrical energy into

No it's same thing. All energy eventually becomes heat and there can be no lost energy in a system. In the case of a GPU we're converting electrical energy into thermal energy, and some mechanical and sound energy due to the fans. So a GPU should just as efficient at producing heat as a space heater, it's just that the electricity goes through a few more steps first.