Solar System Size Calculator Pakistan
Work out how many kW of solar, how many panels, what inverter and how much battery your home needs — using real sun data for your city.
Sun data verified Oct 2026 · Source: European Commission JRC — PVGIS 5.2 (ERA5, optimal tilt) · cross-check on World Bank Global Solar Atlas
Tip: use your highest summer month for full-year coverage, or the 12-month average for net billing.
Lahore: 5.92 peak sun hours/day at 34° tilt facing south (PVGIS).
Heat, dust, wiring & inverter losses. 75% typical.
100% = solar matches your yearly use.
0 hours = on-grid system without batteries. 1 kW ≈ 6 fans + 8 LED lights + fridge. DoD 90% lithium (LFP), 50% lead-acid.
Market estimate as of Oct 2026: roughly Rs 95–120/W for a complete on-grid system. Prices move with the dollar — use your installer's quote.
Formula: 16.67 kWh/day × 100% ÷ (5.92 PSH × 0.75) = 3.75 kW → ⌈3,753.75 ÷ 585⌉ = 7 panels = 4.10 kW
You need a typical 5 kW-class home system. 7 panels of 585 W in Lahore should generate about 545 units a month on average — 109% of your usage. Expect around 20–30% more in May–June and 30–40% less in December–January (shorter days, smog). For net billing your sanctioned load must be at least 5 kW.
| City | PSH | System | Panels | Cost |
|---|---|---|---|---|
| Lahore | 5.92 | 4.10 kW | 7 | Rs 409,500 |
| Karachi | 6.25 | 4.10 kW | 7 | Rs 409,500 |
| Islamabad | 5.88 | 4.10 kW | 7 | Rs 409,500 |
| Peshawar | 5.82 | 4.10 kW | 7 | Rs 409,500 |
| Quetta | 6.83 | 3.51 kW | 6 | Rs 351,000 |
| Multan | 6.23 | 4.10 kW | 7 | Rs 409,500 |
| Faisalabad | 6.05 | 4.10 kW | 7 | Rs 409,500 |
- • Dividing units by 30 and then by 5 or 6 sun hours with no losses — real systems lose about 25%.
- • Sizing for a single summer bill and oversizing for export: under 2026 net billing, exports earn only about Rs 10–11 per unit.
- • Buying an inverter smaller than the AC load you actually run on battery.
- • Ignoring shade from water tanks, parapets or neighbouring buildings between 9 am and 4 pm.
- • Comparing quotes by "kW" only — check panel brand/tier, inverter brand, structure gauge and warranty.
- →Ask for N-type/TOPCon Tier-1 panels with a 25–30 year output warranty.
- →Face panels south at about 30° tilt; raise them for cleaning and airflow.
- →Wash panels every 2–3 weeks in the dusty season — dirt can cut output 10–20%.
- →Shift heavy loads (pump, iron, washing machine, AC) to 10 am–3 pm to use your own solar.
This tool is for informational purposes only. Always verify results with a qualified professional.
What is the Solar System Size Calculator Pakistan?
The Solar System Size Calculator Pakistan tells you how big a rooftop solar system you need, in kilowatts, from either your monthly electricity units or a list of the appliances you run. It then converts that into the number of panels for the wattage you plan to buy, a matching inverter size, the roof space required, optional battery capacity for backup during load-shedding or at night, and a rough installed cost using a price per watt you can edit.
Sizing depends on peak sun hours (PSH) — the number of hours per day the sun delivers the equivalent of 1,000 W/m² onto the panels. This calculator uses PSH values for Lahore, Karachi, Islamabad, Peshawar, Quetta, Multan and Faisalabad taken from the European Commission's PVGIS tool (ERA5 database) for south-facing panels at the optimal tilt: from 5.82 in Peshawar to 6.83 in Quetta. Real systems lose energy to heat, dust, wiring and inverter conversion, so the result is multiplied by a performance ratio — 75% by default, which matches PVGIS's own modelled output for Pakistani cities.
The core formula is: system size (kW) = daily kWh needed ÷ (peak sun hours × performance ratio). Daily kWh is your monthly units ÷ 30, or the sum of watts × quantity × hours ÷ 1,000 for each appliance. Panels = system watts ÷ panel wattage, rounded up. The inverter should be at least the size of the panel array; for hybrid systems that run loads from batteries it must also cover the total wattage you will switch on at once. Battery kWh = backup load (kW) × hours ÷ usable depth of discharge (about 90% for lithium LFP, 50% for lead-acid).
Worked example: a Lahore home uses 500 units a month, or 16.67 kWh a day. Lahore's PSH is 5.92, so with a 75% performance ratio each kW of panels makes about 4.44 kWh a day. 16.67 ÷ 4.44 = 3.75 kW. With 585 W panels that is 7 panels (4.10 kW), which should produce about 545 units a month. A 5 kW inverter fits, the panels need roughly 225 sq ft of shade-free roof, and at Rs 100 per watt installed the system costs about Rs 409,500. Adding 4 hours of backup for a 1 kW load needs a 4.4 kWh lithium battery.
Remember that under NEPRA's 2026 Prosumer Regulations, grid-connected (net billing) systems cannot exceed your sanctioned load, and exported units are credited at a much lower rate than you pay for imports. That makes it smarter to size solar for what you consume during the day than to oversize for export. Use the Solar Payback Calculator to see how your size choice affects savings, and the Electricity Bill Calculator to see what your bill would be without solar.
How to Use This Calculator
- 1Choose whether to size from your monthly units (fastest) or from an appliance list including AC tonnage and hours.
- 2Select your city — peak sun hours for seven major Pakistani cities are built in.
- 3Pick the panel wattage you are quoted (e.g. 585 W) and set how much of your usage solar should cover.
- 4Optionally add battery backup: the load to run and the number of hours.
- 5Enter a price per watt from your installer quote to estimate cost.
- 6Read the recommended kW, panel count, inverter, battery and roof area, then compare cities and share the link with your installer.