Calculate how much your growroom costs on electricity

[john]

First you have to find out how much your electric company charge per unit or killowatt of electric (this amount is usually on your electric bill).
A killowatt is a 1000w. So for example a 600w hps is .6 of a killowatt.

(X) = the cost for a unit/killowatt of electricity, ie. if it's 15 pence, the answer is (.15).
(Y) = the watts used by the item, ie. 250w hps uses roughly 250w per hour (.25 of a killowatt), the answer is (.25).
(Z) = the amount of hours per day that the item will be using electric, ie. if it's 18 hours per day, the answer is (18)

Multiply each of these to show how much you pay per day for your item

(X) x (Y) x (Z) = the price you pay for the item per day

[Daniel.]

(Watts X Hours of Operation / 1000 X Cost per Kwh X 30 (Days)