It been my experience that unless someone has a lot of aquariums or runs electricity hogs like metal halide lights and such that a lot of people overestimate how expensive their tanks are in relation to their overall power bill.
Yeah, I agree. I estimate my tank , a 4 foot 120 gallon, other than heating(Which it's overheating all summer) uses about $15-25/month in electricity. That's nothing compared to the normal bill of $300.