I suggest the government to make alternative imprisonment in kwh as well. Put electricity generating devices in prisons (bicycles, fitness machines that would spin turbines instead of moving weight). And the prisoner can be given an alternative sentence in kwh instead of days.
I still think this solution would be appropriate for crimes of gross negligence (where you cause a fatal car accident on the road, sober, etc.), because these people are not really for prison, but I agree that they should be punished, and the punishment would be the production of electricity.
This gets rid of the prison crowds and at the same time starts making money for the prisons. At the same time, more exercise would make people healthier.