We estimate $15 on average. Below is the wattage of each system: Eden Garden Wattage = 220 watts 108 kilowatt/hr per a month Eden Tower Wattage = 50 watt lights per layer Tier 1= 24 Kilowatt/hour per month Tier 2 = 48 Kilowatt/hour per month Tier 3 = 75 Kilowatt/hour per month Tier 4 = 96 Kilowatt/hour per month