My electric bill is normally around $80/month with no rigs crunching. Right now it is around $180.00 (this was before the third HD 7970 was added).
Back in 2010 I had 5 i7 920 rigs crunching and my bill reached close to $300/month
That caused me to reduce my rigs pretty quickly. I will be curious what my bill will be this month...
Thankfully the misses doesn't see this bill or she would have another reason to complain about my "hobby" (they are too loud, they heat up the apartment, etc...)