Researchers have built server prototypes that re-use old components

The one downside I've found (other than noise) running a super old supermicro at home is the power consumption is nowhere near as good as the modern hardware. But my server is _really_ old, some dual socket xeon thing I got super cheap.

Weird question, if you put an old, inefficient server somewhere sensible, could it reasonably pull double-duty as a heater? If you're pumping a kilowatt or two into it, that's enough to warm up a decent sized room!

It's not as efficient as a heat pump nor as cheap as burning natural gas but yeah you can use it as a space heater

I have a hybrid water heater that uses a heat pump to suck heat out of the air to warm my water.

I placed my homelab next to it so that at least my waste heat gets used in the most efficient manner that I have.

I guess... I have mine in a fairly small room and that room definitely gets warm, but actually harvesting that heat in a meaningful way in a useful room I dont think so.