With last week's big rental income, I've now fully ROI'd my Antminers and PSU.  Unfortunately, since my MIL is coming tonight and moving into the room where the units live (and where power is included in my rent), I may be going idle for a while. 

Free power is nice.  The fun thing is learning that even with my 1KW PSU running full bore, my usage is still less than the average usage in my building.