This is a very general system size estimation. Other factors such as peak load, shade, location, available panel space, and seasonal use need to be taken into account. For the most accurate and personalized off-grid system size calculation, call our solar experts at 1-800-472-1142. We want to help you get the system that's right for you. Use this solar calculator to determine a precise system size for your actual energy use. 1. Your kWh used per year (no commas): 2. Solar Hours per Day (see map below): The NEXT STEP, now that you have an estimate for the desired kW, VIEW SOLAR KIT SIZES to compare prices, brands and, options.