Running a typical compact florescent 13 watts (or the brightness of a 60 watts incandescent light bulb) costs
9.36kw = $1.22/month = $14.60/year
Most of photo sensing doesn't work well with CF, the on-off cause flickers and burning up light bulbs instead.
The alternative solution would be using timer devices, 12 hours on/off = $7.00/year.
