I've always found it interesting that electric radiators are 100% efficient but if you treat a computer as a radiator then you get the same 100% efficiency but extra computations done on top.
Physics must have a word for how energy in forms such as electricity can do work, but once transformed into thermal energy it can no longer do work (a temperature difference is required to perform work, and then only at carnot efficiency — a temperature alone cannot perform work).
I asked on reddit once, and someone suggested "exergy" but I think that word is explicitly concerned with heat, so couldn't be used to say things like "1000w of electricty provides more exergy than 1000w of gas", or "An electric space heater destroys the exergy of the electricity it consumes, while a computer uses it for computation".
So is there a word?
"Energy is conserved, but it can change forms. If you have energy in a low-entropy form, you can do useful work with it. You can lift something up, drive a car, or fly an airplane. If you convert that energy into a high-entropy form, it becomes useless.
A low-entropy concentration of energy is called fuel. We have fossil fuels sitting in the ground with energy in them in a concentrated form. We can extract the energy because the entropy of the fuel is low. Once we burn the fuel, we cannot go back. You can heat a room in your house by burning wood, but you cannot cool off a room in your house by unburning fuel and turning it into wood."
And of course if you use a computer then X% will go into the computation. The reason why it might be cost efficient for you is because the server guy thinks he has the same costs for electricity no matter if the server is in the data center or in your home, and therefore pay your bills for the server heater.
You get also 100% conversion with a normal lamp or a sound system (unless they are very close to a window). You get all the heating, and the light or music for free.
However, I will admit that my comment did not add anything useful to the discussion.