40 cents per 1000 watts. If you run your 400 for 12/12 and two 125 watt CFL's ( must be HUGE ones) it comes to 650 watts total. so 650/1000=.65 KW so take 40 * .65=26 cents per hour of use is the cost. so for a whole day of 12/12 its gonna cost you $3.12 and for a whole month about $95.
You have expensive electrical rates, mine is only 4 cents per KWH. 3600 watts costs less than $100 per month