Solar Panel Size Calculator
Enter your monthly electricity consumption to find out how many solar panels your home needs. A household using 500 units/month needs approximately a 4 kW system — about 7-8 panels of 550W each, covering 150-180 sqft of roof space.
Calculate Your Solar Panel Requirement
Solar System Sizing Guide — Units to Panels
| Monthly Units | System Size Needed | Panels (550W) | Roof Space | Approximate Cost |
|---|---|---|---|---|
| 200 | 1.5 kW | 3 panels | 66 sqft | Rs. 250-350K |
| 300 | 2.3 kW | 4-5 panels | 88-110 sqft | Rs. 350-500K |
| 500 | 3.8 kW | 7-8 panels | 154-176 sqft | Rs. 600-800K |
| 700 | 5.4 kW | 10 panels | 220 sqft | Rs. 850K-1.1M |
| 1,000 | 7.7 kW | 14 panels | 308 sqft | Rs. 1.2-1.6M |
Factors That Affect Your Panel Count
The sizing formula is simple: divide your monthly units by 130 to get the kW system size needed. This assumes Pakistan's average 5 peak sun hours per day and accounts for system losses (dust, temperature, inverter efficiency). Then divide the kW by the panel wattage (typically 0.55 kW for a 550W panel) to get the number of panels.
Why 130? A 1 kW system in Pakistan generates approximately 130-150 units per month (1 kW × 5 sun hours × 30 days × 0.85 efficiency = ~127.5 kWh). We use 130 as a conservative estimate that accounts for real-world losses.
Roof orientation: South-facing roofs generate maximum output. East/west-facing roofs produce 15-20% less. North-facing roofs in Pakistan are poor for solar — add 25-30% more panels to compensate.
Shading: Trees, neighboring buildings, or rooftop water tanks casting shadows on panels reduce output significantly. Even partial shade on one panel affects the entire string in a series-connected system.
Temperature: Pakistan's 40-50°C summer temperatures reduce panel efficiency by 10-15%. Panels perform best in cool, sunny conditions — winter in Punjab is actually the highest efficiency period despite shorter days.
Calculate savings: solar savings calculator. Net metering guide: how to apply. System comparison: on-grid vs off-grid vs hybrid. Roof suitability: is your roof suitable?.
Add 20% buffer: Always size your system 15-20% above your calculated need. This accounts for dust accumulation between cleanings, seasonal variation, and future consumption growth. A system sized exactly to current consumption leaves no margin.
Sizing Examples for Common Pakistani Homes
Small home (5 Marla, 2 ACs): Typical consumption 400-600 units. Needs 3-5 kW system (6-9 panels). Roof space required: 132-198 sqft — easily fits on a 5 Marla roof with room to spare.
Medium home (10 Marla, 3 ACs): Typical consumption 700-1,000 units. Needs 5.5-8 kW system (10-15 panels). Roof space: 220-330 sqft — fits comfortably with south-facing placement.
Large home (1 Kanal, 4+ ACs): Typical consumption 1,000-2,000 units. Needs 8-15 kW system (15-28 panels). Roof space: 330-616 sqft — may need optimal panel placement to fit the full array.
If your roof can't fit enough panels, consider higher-efficiency panels (N-Type at 22-24% efficiency produce more per panel) or ground-mounted systems if you have yard space.
Estimates only. Calculator results are approximate. Actual amounts vary based on your specific provider, location, and applicable rates. Use for planning — verify with official sources.
Solar Panel Sizing — Homeowner Questions
Approximately 7-8 panels of 550W each (3.8-4 kW system). This covers about 150-180 sqft of roof space and costs Rs. 600,000-800,000 for an on-grid system.
Yes, if your inverter supports it. Buy an inverter rated for your eventual target size, install fewer panels initially, and add more later. This only works with string inverters that have multiple MPPT inputs or with micro-inverters.
Not necessarily. The fastest payback comes from a system sized to match your consumption — not larger. Excess generation through net metering earns credits at potentially lower rates than what you save by reducing grid consumption.