Engineering CalculationSolar Panel, Battery & Inverter Size Calculator
Size the solar array, battery bank and inverter for a home, office or plant load from its daily energy use and backup need.
Open the calculator →Formula
Panel kWp = daily kWh / (peak sun hours × system derate)
Battery Ah = backup kWh × 1000 / (battery V × depth of discharge × efficiency)
Worked example
20 kWh/day, 5 peak sun hours (use your site value), derate 0.75
Array = 20 / (5 × 0.75) = 5.33 kWp
10 kWh backup on 48 V, DoD 0.8, efficiency 0.9: Battery = 289 Ah
Where engineers use it
- Rooftop solar for homes and factories
- Off-grid and hybrid systems
- UPS / inverter battery sizing
How to use
- Click Open the calculator. It runs free in your browser, on desktop or phone.
- Enter your values. Units and typical ranges are shown next to each input.
- Read the result and the step-by-step working, then print or add it to your Project BOQ.
Questions
Does it calculate return on investment?
Yes, the Rooftop Solar PV ROI calculator in the Electrical suite works out payback for on-grid systems.