Just let me tell you that whoever is paying for that electricity will notice the consumption increase. Which means that if you don't have the permission to use the computers for mining you will get caught.
+1 to that. Electricity is never 'free' and it will be quite a jump in costs when their next bill comes.
I used to do consultancy work for a company which generated electricity as a by-product of their main product, some sort of polymer. They sold some of it to the electric company, but those guys would only want to buy so much.
They didn't bother to turn off their screens, and the lights were always on, because, quite frankly, it was energy that would've gone to waste anyway.