Not sure I like this idea. It reduces the incentive to make electronics more efficient so they don't waste so much energy in the form of heat. And when I think about the idea it is going to be 92°F today where I live and my AC will be working to remove heat from my house, I sure would not want something designed to pump heat into my house working against my AC. Now I don't supposed many homes in the Netherlands have AC, so that may not be an issue there. But what happens if the homeowner sells the home? Who pays for electricity to run this server 24/7/365? To me, it would make more sense to put these servers in public buildings, not private homes.
