I'm paying about 0.03$/kw for my electricity which is really low. I live in an apartment with two other guys and we split the electricity bill (they have no idea I have few ants running on my balcony 
)
)That's a pretty assholish thing to do. Imagine what they will do when they find out you are taking advantage of them.
Propably yea although running two S3's with one 750W PSU doesn't use much power : )
If I'll expand the mine more I'll have a discussion with them : )