Size your solar system in a few minutes

Divide your daily energy use (kWh) by your peak sun hours and a 0.8 performance factor for heat, dust, wiring and inverter losses. That gives the array size in kWp; divide it by the panel wattage (585 W by default) and round up. Example: 12 kWh a day ÷ (5 sun hours × 0.8) = 3 kWp, or six 585 W panels.

It depends on how much power your AC draws and how long it runs. Read the rated input power on the AC’s nameplate (an inverter AC draws less once the room is cool) and add it to the calculator with its daily hours. Example: an AC drawing 1,500 W for 8 hours uses 12 kWh a day, which needs about 3 kWp – six 585 W panels at 5 peak sun hours. The calculator also allows for the AC’s start-up surge when it sizes the inverter.

The calculator takes the largest of three values: your running load plus 25% headroom, the starting surge of your largest motor appliance (fridge, AC, pump – about three times its rating for a moment), and the solar array size divided by 1.3. The result is rounded up to the next standard inverter size.

For hybrid and off-grid systems the battery covers your night-time use or your chosen backup hours at average load, whichever is larger. This is divided by 0.9 (usable depth of discharge) and 0.95 (battery efficiency) and rounded up to whole 5.12 kWh battery modules. Example: 5 kWh at night ÷ (0.9 × 0.95) ≈ 5.9 kWh, so two modules. On-grid systems have no battery.

On-grid systems work with the WAPDA / K-Electric grid and can export surplus units with approved net-metering, but switch off during load-shedding. Hybrid systems add batteries, so essential loads keep running when the grid is off. Off-grid systems run fully on solar and batteries without a grid connection.

Use the units (kWh) consumed in a month. For sizing, a high-use summer month gives a safer result than a winter month.

The number of hours per day of full-strength sunlight a panel receives on average. The calculator uses 5.0 hours by default; the real value depends on your location, season, panel angle and shading, so you can change it.

No. It sizes your system only and is an estimate to help you plan. Our team confirms the final design after discussing your load, roof and budget, and gives you the current price. Use “Send to FAJR for a quote” to share your result with us.