First of all the size unit your business requires depends on a few things. Number 1, how many square feet is your business. The size of your business may not be the most urgent. However Number 2, what are the most urgent electrical applications at your office, warehouse, or job site? Once you have done the sizing and math for these 2 factors. Florida Power Solutions will calculate the amount of wattage. You will need to suitably supply you with power in the case of an outage or service halting.