With hardware like the Spark and Strix, the water usage is known to be zero, yea?

On the energy front, I assume less efficient, but I also think there is a tradeoff in efficiency versus freedom, that's why I have my own hardware.

The electricity used by hardware itself consumes water. When people talk about data center water usage they're often also including the water used in electricity generation.

All consumer hardware (not counting XOC) uses either air cooling or closed-loop liquid cooling, so the water usage is zero, always. Power is a little trickier. I'd assume it's less efficient, but also the total usage is less, because the user sometimes turns the machine off, and the hardware idles to a deeper sleep state than server hardware.