Solar for 300, 600, 900 or 1,200 Units: System Size, Panels and Roof Space
The kW size, number of 585 W panels, roof space, rough cost and payback for four household bills in Pakistan.
By the TurantTools PK team · Updated 28 October 2026 · 2 min read
Before getting solar, three questions matter: how many kilowatts, how many panels and how much roof. The table shows all three for your monthly units.
Solar system size by monthly units
| Units a month | System | Panels (585 W) | Roof space | Rough cost | Payback (years) |
|---|---|---|---|---|---|
| 300 | 2.5 kW | 5 | 15 m² | Rs 275,000 | 2.1 |
| 600 | 4.5 kW | 8 | 27 m² | Rs 495,000 | 2.1 |
| 900 | 7 kW | 12 | 42 m² | Rs 770,000 | 2.1 |
| 1200 | 9 kW | 16 | 54 m² | Rs 990,000 | 2.1 |
Payback is about the same at every size, because cost and saving both grow with the system. What really changes it is how much power you use in the day and what you pay for grid power.
Roof space
- Allow about 6 square metres of clear, sunny roof per kW, so there's room to clean and walk between panels.
- Shade from a water tank, a stair room or a tall neighbouring wall cuts output.
- Panels facing south at a gentle tilt make the most power.