Free professional solar system design calculator. Calculate solar panels, inverters, batteries, and electrical components. Most countries are working hard to use green. Photovoltaic (PV) systems (or PV systems) convert sunlight into electricity using semiconductor materials. It can also generate electricity on cloudy and rainy days from reflected sunlight. The mode changes what you provide (e., daily vs monthly load, or target kW vs usage-based sizing). 🌞 What Is an Off-Grid Solar System? An off-grid system operates independently from the national power. 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.