How many solar panels fit on my roof?
Enter each roof face you could use. The calculator lays out real panel sizes in portrait or landscape, whichever fits more, then estimates the system size and yearly output for your city, roof direction and pitch.
How many solar panels fit on your roof?
Measure each roof face you could use: its length along the gutter and its depth up the slope to the ridge. Leave out areas under chimneys, vents, satellite dishes or shade from trees and neighbouring buildings.
Panels cover about 23,2 m². A planning estimate only: it assumes an unshaded, rectangular face and panels mounted flush with the roof. An installer's site visit confirms the layout, structure and shade.
Get your roof assessedYearly output by city and roof direction
Estimated kWh a year for each kWp of panels at a typical 26° roof pitch. Multiply by your system size: a 5 kWp system on a north-facing Johannesburg roof, for example, gives about 8 755 kWh a year.
| City | North | NE | NW | East | West | South |
|---|---|---|---|---|---|---|
| Johannesburg | 1 751 | 1 689 | 1 658 | 1 510 | 1 465 | 1 135 |
| Pretoria | 1 732 | 1 656 | 1 662 | 1 479 | 1 481 | 1 133 |
| Cape Town | 1 681 | 1 597 | 1 626 | 1 411 | 1 452 | 1 095 |
| Durban | 1 484 | 1 402 | 1 420 | 1 229 | 1 251 | 937 |
| Gqeberha | 1 613 | 1 515 | 1 557 | 1 312 | 1 372 | 991 |
| Bloemfontein | 1 813 | 1 744 | 1 718 | 1 546 | 1 507 | 1 134 |
| Polokwane | 1 716 | 1 644 | 1 658 | 1 479 | 1 496 | 1 165 |
| Mbombela | 1 526 | 1 440 | 1 482 | 1 277 | 1 332 | 1 009 |
Source: PVGIS 5.2 (European Commission JRC), PVcalc, crystalline silicon, 1 kWp, 14% system losses, fixed mounting, retrieved 2026-09-26. Figures assume no shading.
How the calculator works
Each roof face is treated as a rectangle. After the edge clearance you choose, the calculator fits panels in rows with a 20mm gap for clamps, tries both portrait and landscape, and keeps whichever fits more. Panel sizes come from manufacturers' datasheets: JA Solar JAM54D40, 435–460W at 1.762 × 1.134 m; JA Solar JAM72D40, 580–605W at 2.278 × 1.134 m; Jinko Tiger Neo 66HL4M-BDV, 605–630W at 2.382 × 1.134 m.
Output uses the European Commission's PVGIS model for the nearest listed city, the roof direction and the pitch, with 14% system losses. Real systems differ with shade, dust, temperature, inverter sizing and how the strings are wired.
What it can't see: hips, valleys, skylights, vents, the roof structure, local wind-zone clearance rules or shade from trees and buildings. Leave shaded or obstructed areas out of your measurements, and treat the result as a starting point for an installer's site visit. Flat roofs need tilted frames with space between rows, so they fit fewer panels than this estimate.
Roof and panel questions
How much roof space does one solar panel need?
The panel itself: about 2,00 m² for a compact 435–460W panel, 2,58 m² for a common 580–605W panel and 2,70 m² for a 605–630W panel, based on the manufacturers' datasheets. Allow extra for clearance from the roof edges and small gaps between panels.
Which roof direction is best for solar panels in South Africa?
North. In PVGIS data for Johannesburg at a typical 26° pitch, an east-facing roof produces about 86% and a west-facing roof about 84% of what a north-facing roof does, and a south-facing roof about 65%.
Can I put solar panels on a south-facing roof?
You can, but each panel produces noticeably less, so it takes more panels to reach the same output. Use north, east and west faces first, and treat south as a last resort after checking the numbers.
How many panels do I need for a 5kW system?
About nine 590W panels (5.3 kWp) or eleven 450W panels (5 kWp). The inverter size (5kW) and the panel array size (kWp) are different numbers, and many 5kW systems carry more or fewer panels depending on the budget and the roof.