Look at your bill and see how much they charge per KW/hr. The T5's use minimal electricity, might see an increase of a dollar or so a month. Same with the fans. By the way speaking of the T5's, don't get 2ft T5's I'd get 4ft. I am pretty sure the last 3-6in at both ends of a T5 tube don't light as well as the center. At least in my experiences the plants at the end don't get as much light. Anyways I digress, a 1000watt light uses 1kw per hour. So do the math. If you are charged 10 cents a kw per hour (which is kinda high, I think I pay an avg of 7.9 cents per kw/hr. It differs depending on the time of day), it would cost you $1.20 a day if you run a 1000watt light for 12hrs daily. That same light would cost $1.80 to run 18 hours a day.