Accurately estimating your electrical usage from an indoor grow: Take your total watts. It helps to group items on the same timer together. Take the number of hours per day you are running each group of items. Calculate the percentage of the time each group is turned on. Multiply by that % figure to get an average hourly watt usage, then by 24 to find total daily watt usage for each group. Add the value for all groups together. Multiply by the number of days in your billing cycle (one month). That is your WATT HOURS per month. Divide by 1000. That is your kwh per month. Multiply by your charge per kwh. That is your bill. Example: A grower has a 1000 watt flower room on 12/12, a 400 watt veg room on 18/6, a 150 watt clone chamber on 24/0, a 500 watt air conditioner running all the time, and a blower on each room that draws 20 watts and is on only when the lights are on. (this is just an example mind you) Group 1 is the shit that is always on: -a/c @500w -20w blower for clone room -150w clone chamber lights Your daily draw is all of that, straight. 670w x 24 = 16,080 watt hours per day used Group 2 is the 18/6 area: -20w blower -400w light 18 is 75% of 24 so .75 x 420 gives the total daily draw for that room: 315 watts x 24 = 7,560 Group 3 is the flower room on 12/12: -1000w light -20w blower They are on 50% of the time and 1020 x 0.5= 510w, x 24= 12,240 Add all that together: 12,240 7,560 16,080 ______+ 35,880 That's 35.88 kilowatt hours per day, and there are 30 days in your cycle, so 1076.4 kwh per month. Say your charge per kilowatt hour is $0.23 Your growroom will cost you $247.57 per month to operate. Add 10% for small shit like pumps and oscillating fans.