5W vs 50W is an annual difference of 400 kWh. Or 150 kG CO2e, if that's your metric. Either way, it's not a huge cost for most people capable of running a 24/7 home lab.
If you start thinking about the costs - either cash or ghg - of creating an RPi or other dedicated low power server; the energy to run HDDs, at 5-10W each, or other accessories, well, the picture gets pretty complicated. Power is one aspect, and it's really easy to measure objectively, but that also makes it easy to fetishize.