System size depends on factors like your energy consumption, roof space, and location. Our reports will include multiple options to find the right fit for you. For a quick rough estimate you can take your total energy consumption (kWh) for the year and divide it by 1.35. For example: 15,000 kWh/year divided by 1.35 = 11,111 W. Or 11.1 kW. This would provide a 100% offset of your consumption.