A typical 2–3 bedroom home consuming 400–600 kWh/month needs 8–16 panels (450W each) in a sunny location like Dubai or Tehran, or 14–22 panels in a lower-irradiance location like London. The exact number depends on your monthly consumption, city, panel wattage and system efficiency — use the calculator above with your actual electricity bill figure for a precise result.

Off-grid systems operate with no utility connection at all — 100% of your energy comes from panels and batteries. This requires a larger battery bank (typically 3–5 days of autonomy) to survive cloudy periods. Hybrid systems keep a grid connection as backup, so batteries only need 1–2 days of autonomy — significantly reducing battery cost while still providing outage protection.

Check your electricity bill — it lists monthly kWh consumed. Use a 3-month average for better accuracy, as consumption varies seasonally. As a guide: studio/1-bed apartment 150–300 kWh/mo, 2–3 bedroom home 350–600 kWh/mo, large family home 700–1,500 kWh/mo, small office or shop 400–900 kWh/mo. If you don’t have a bill, use the appliance builder in the calculator.

Battery capacity depends on your daily consumption and how many days of autonomy you want without sun. For a hybrid system covering outages, 1–1.5 days is usually sufficient. For off-grid, 2–3 days is typical. The calculator adjusts battery sizing automatically based on your selected autonomy days and system type. LiFePO4 batteries allow 80–90% depth of discharge vs 50% for lead-acid — fewer kWh of LiFePO4 can replace more kWh of lead-acid.

The inverter must handle your peak instantaneous load, not just average consumption. Add up the wattage of all appliances that could run simultaneously — especially motors (pumps, ACs, fridges) which draw 2–3× their rated wattage on startup. As a rule, size the inverter at 125% of your total peak load. The calculator outputs a recommended inverter size based on your appliance inputs.