I would have a word with the man himself first. As you said he is a renter and the problem may be beyond his control and he just wants a bit of electric until the problem is resolved. If you are happy for him to do that in the short term and you think he is using it safely, you could suggest he contributes to the cost.
I cant think of another innocent/reasonable use of it, so if hes taking the Pee, contact the owner. I would like to think that would be the end of it, if not , then AYDEM.