DC/AC ratio, also called inverter loading ratio (ILR), is the array's STC power divided by the inverter's AC nameplate power. ILR = P DC, STC / P AC, rated. A higher ILR feeds more energy during long shoulder hours and in winter, at the cost of some midday clipping on clear . DC/AC ratio and inverter loading shape real solar yield more than most design choices. Set them well and you gain energy all year, keep the inverter in its high-efficiency zone, and leave headroom for grid support and batteries. Formula: Required Inverter (W) = Load × Surge × (1 + Margin%). Divide by 1000 for kW or use phase factor for split-phase systems. In this section, we will cover the basics of inverter load calculation, including the different types of inverters and their load. The load is calculated by enumerating all appliances together with their power ratings and operational hours, thereafter adding these values to derive the total average energy demand in watt-hours or kilowatt-hours. more Are you confused about how to properly size a solar power system? In this video, I an example step-by-step solar system sizing —. This tool assists users in determining the appropriate inverter size by calculating the total power demand of selected appliances.