This would be hella interesting, I imagine it would be several 1000x magnitude less. You could have a witness node ran entirely off green power too, whereas watt for watt I imagine this gets harder (solar for example) with POW coins like Bitcoin. Average top end ASIC/GPU miner is drawing 100/180W*> MIN, so I guess you could squeeze 2 miners per solar panel for example, if it output around around 265-350W...