> Many home labs also don't use the newest hardware but old server hardware (add 10 - 40 watt idle).

Yes, but switching to newer, more efficient hardware is not free, so you need to factor this in when considering a switch. Also, in case you don't only care about your wallet but also environmental impact it's getting even more complicated, since manufacturing your new shiny toy definitely is polluting the environment somewhere in Asia, gets shipped via ship burning horribly dirty fuel in international waters etc.

If you don't have any use for the old hardware, chances are it will end up burning on some open field somewhere in Africa after local recyclers already extracted the good stuff...