Solar Panel Count
You cannot cover the whole roof. Access paths, shading gaps and equipment leave about 80% usable. Divide by the area of one panel and multiply by its output for the installed capacity.
Your numbers
Panels
24
Installed capacity
10.8kW
Area
47.73m²
Formula
Panels = Roof area × 0.8 ÷ (Panel width (m) × Panel height (m))
Actual generation depends heavily on orientation, tilt and sunshine hours, not just capacity. This sizes the array, nothing more.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Roof area (m²)The roof’s horizontal plan area, seen from above. | 60 | 0 and up |
| Panel width (m)The width of one panel. | 1.13 | 0.1 and up |
| Panel height (m)The height of one panel. | 1.76 | 0.1 and up |
| Installed capacityPanels times output — the installed capacity. | 450 | 1 and up |
Step by step
Quick reference table
Results when only Roof area (m²) changes and everything else stays put.
| Roof area (m²) | Panels | Installed capacity (kW) | Area (m²) |
|---|---|---|---|
| 30 | 12 | 5.4 | 23.87 |
| 45 | 18 | 8.1 | 35.8 |
| 60 | 24 | 10.8 | 47.73 |
| 90 | 36 | 16.2 | 71.6 |
| 120 | 48 | 21.6 | 95.46 |
What each result means
| Result | At default values |
|---|---|
| PanelsHow many panels the roof can actually take. | 24 |
| Installed capacity (kW)Panels times output — the installed capacity. | 10.8 |
| Area (m²)The space a shape covers — length squared. | 47.73 |
Common mistakes
Actual generation depends heavily on orientation, tilt and sunshine hours, not just capacity. This sizes the array, nothing more.
Glossary
- Roof area
- The roof’s horizontal plan area, seen from above.
- Panel width (m)
- The width of one panel.
- Panel height (m)
- The height of one panel.
- Installed capacity
- Panels times output — the installed capacity.
- Panels
- How many panels the roof can actually take.
- Area
- The space a shape covers — length squared.
Frequently asked questions
Q. How is Solar Panel Count calculated?
Panels = Roof area × 0.8 ÷ (Panel width (m) × Panel height (m)) — You cannot cover the whole roof. Access paths, shading gaps and equipment leave about 80% usable. Divide by the area of one panel and multiply by its output for the installed capacity.
Q. Can you walk through an example?
With Roof area 60m², Panel width (m) 1.13, Panel height (m) 1.76, Installed capacity 450, the answer is Panels 24.
Q. What do I need to enter?
Enter Roof area, Panel width (m), Panel height (m), Installed capacity. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Roof area (m²) moves the answer to Roof area (m²) 30 → Panels 12 and Roof area (m²) 120 → Panels 48. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Actual generation depends heavily on orientation, tilt and sunshine hours, not just capacity. This sizes the array, nothing more.
Related calculators
Keep your length units consistent across inputs — mixing centimetres and metres throws results far off.