Depends on what you are paying per kilowatt hour. At my residential 8k it cost around 1800 a month, thats 8x1000w de hps, ac, 2 70 pint dehums, 9 fans, co2 burner and controller, blue lab guardian. Mine is .34 per kilowatt hour. At my commercial site, its 1/3 of the cost at .11 per kilowatt...