Power costs is only a concern for miners using old technology. ASIC miners only have to worry about price per Ghash/s, because power costs will be negligible compared to their initial investment.
Power cost
does matter, but it's negligible for single device, or small-scale mining. Scale the issue up, and you will be forced to consider those costs more seriously.
Wrong.
If you buy one, two or a hundred ASIC miners, the initial costs vs power consumption equation comes out exactly the same. Small or large scale makes no difference at all.