you take the total amount of wattage you are using for your lights. you divide that by 1,000. you then take whatever your utility co chargs per kilowatt hour and multiply that by the answer to the first part and then multiply by the amount of hours they run. for instance: In one of my setups I have a 400W HPS and 4x65W Flourex Floods (great lamps by the way!!!) for a total of 660W 660W divided by 1,000 = .66kW so, we'll just assume that my utility company charges $.02/kw hour (check your bill, it will say) .66kW x .02 x 18 hours = 24 cents a day or about 7 bucks a month

Exactly. Good explanation, up4anything. Remember with cfl's to use the true wattage in your calculation, that should be the lower wattage number on the package (and the only one printed on the bulb or ballast), that lower wattage and hence lower energy cost is the whole idea behind cfl's in the first place. For total energy use and cost for your grow don't forget to add in fans and any other electrical devices. In some areas electricity costs are different at different times of the day. My bill doesn't even tell me my unit rate, but I can just take my total usage charge and divide by the kilowatts used to get the number.

up for anything..."Is it wrong to masturbate to pics of pot?"seriously i just laughed for like 5 mins after reading that haha wow funny guy

Look First make watt to Kw/h 2x150w=300w so 300:1000=0,3 Kw/h Then you should know how much cost 1 Kw/h...example : 1 $ So if you got plant in veg. ...then 18 h. at day and example 28 days in month. Two lamps taking 0,3 $ in 1 h. So at 18 h sum would be 5,9 $...28 days...-151,2$. ---- Formula ((I:1000)*M)*T=X I-Item watt'age. M-Price per 1 Kw/H. T-Time item will be on. X-Price of specificated item which used some electricity amount on specificated time period. ---- I hope this helps i wrote it my self ...mini guide...^^

Don't forget that you are also running fans and such that could be calc. into that... won't make a big difference