Look at what you pay per kilowatt hour. Many companies have an elevated scale--the more you use, the more you pay. Watts=Amperage times voltage. Take the amperage of your equipment (lights, fans, pumps, etc), multiply times your voltage and this is your watts. Divide by 1000 and this is kilowatts. Figure out how many hours a day you will be powered up and multiply this times your kilowatts. These are kilowatt hours. Multiply by you kilowatt cost and this gives you daily costs for your equipment.