If you don’t close the box of the system at some point to isolate the input, efficiency would be meaningless. I think in the context of the original post, suggesting running a server in winter would be a zero-waste endeavor if you need the heat anyway, it is perfectly clear that the input is electricity to your home at a certain $/kWh and gas at a certain $/BTU. Under that premise, it is fair to say that would not be true if you have a heat pump deployed but would be true compared to gas furnace in terms of efficiency (energy consumed for unit of heat), although not necessarily true economically.