To be honest, the miner rig will draw quite a bit of current. Did you consider that bitcoins get harder/less profitable to generate and electricity prices are going up? What's the current situation? And if it is profitable right now, for how long will it be before you'll save money by keeping those servers offline?

Electricity is a big cost for running servers, way above bandwidth in normal situations and not far from the cost for the hardware over its life-cycle.

If it lasts long enough to pay for the hardware, I guess go for it.