parker679 wrote:It would depend on the wattage of the bulb you use, how many bulbs, how long you run them for, and what your kwh rate is.
Edit: Somebody correct me if I'm wrong but I believe it will be (# of bulbs)(bulb wattage)(hours of operation per day)(30), this will give you the total watts used per 30 days. Divide this number by 1000 to get the total kW used and then multiply that number by what you pay your utility provider per kWh.
Thats correct. To break it down for a single light with two bulbs... standard T8 will be 32+32=64 watts. At say 16 hours, you're looking at 1,024 watts or 1.024 kWh. Multiply that by the cost of a kWh in your area, I believe mine is 8 cents, but they do vary. Times 30 days would be roughly $2.50.