Hey tokinkracker,Heres the math.KILOWATTS, wattsxhours=total watts per day, divide total watts per day by 1000=total killowatts per day,multiply the killowatts days x the cost per killowatt to get the total cost per day.Killowatts per day x 30 days = cost per month. 1000x 18 =18000, 18000 divided by 1000 =18.killowatts per day, multiply 18. x your cost of a killowatt = cost per day.cost per day x 30 days = cost per month. Cost per killowatt hour is on your electric bill. Hope that helps.PEACE