is there a formula to figuer out how much money a month it will cost to run a 400 watt HPS light 18/6?
Depending on how much your electricity is, mine is like 7.45 cents per kilowatt hour. One kilowatt hour is 1000watts for one hour. So, 400 watts at 18 hours a day, at 30 days a month(average), divided by 1000(one kilowatt hour) is 216 kilowatt hours a month. Multiply 216 x .0745 = $16.09. So 16 dollars and 9 cents a month IF your power is 7.45 cents a kilowatt hour like mine is. Pretty simple formula, can swap numbers in and out depending on what your total wattage is. Should look at what your fans, all your lights and everything pull add it all up then run it throught he formula to get a more accurate cost.