Your result
Click Calculate
Enter your values, then click Calculate result.How this calculator helps
Convert usable, shade-free roof space into a preliminary panel count and system size. An allowance for walkways, edges and maintenance access is applied before dividing by the footprint of one panel.
How to Size a Solar System in Pakistan
Calculate solar kW, panel count, inverter capacity and realistic generation from your own electricity use.
Read the complete guide →How to use it
- 1
Measure only structurally usable roof area.
- 2
Allow for walkways, edges, shade and fixed obstructions.
- 3
Enter the planned panel footprint and wattage, then confirm with a physical layout survey.
Formula and methodology
Usable installation area = measured roof area × layout factor. Panel count = usable installation area ÷ panel footprint. Capacity = count × panel watts.
Uses editable energy demand, sunlight, equipment and loss assumptions. It is a planning model rather than a site survey or electrical design.
Worked calculation example
A 1,000 sq ft roof with 75% usable layout area and 28 sq ft per panel fits about 26 panels, or roughly 15.1 kW using 580 W modules.
How to interpret your result
Estimate how many solar panels fit on usable roof area and the corresponding array capacity. Read the main result together with the supporting values rather than treating one number as a guarantee. The disclosed method is: Usable installation area = measured roof area × layout factor. Panel count = usable installation area ÷ panel footprint. Capacity = count × panel watts.
Input guide
Measure only structurally usable roof area.
Allow for walkways, edges, shade and fixed obstructions.
Enter the planned panel footprint and wattage, then confirm with a physical layout survey.
Scenario comparison
| Scenario | What it demonstrates |
|---|---|
| Worked baseline | A 1,000 sq ft roof with 75% usable layout area and 28 sq ft per panel fits about 26 panels, or roughly 15.1 kW using 580 W modules. |
| Shade paths check | Tanks, walls and nearby buildings may reduce usable area at different times. |
| Structural loading stress test | Roof strength, wind loading and mounting points require professional assessment. |
Common mistakes to avoid
- Ignoring shade paths: Tanks, walls and nearby buildings may reduce usable area at different times.
- Overlooking structural loading: Roof strength, wind loading and mounting points require professional assessment.
- Failing to test access and setbacks: Maintenance routes and safety clearances prevent covering every square foot.
Check the result against equipment datasheets, a site survey and a written design from a qualified solar professional.
What can affect the result?
Shade paths
Tanks, walls and nearby buildings may reduce usable area at different times.
Structural loading
Roof strength, wind loading and mounting points require professional assessment.
Access and setbacks
Maintenance routes and safety clearances prevent covering every square foot.
Limits of this estimate
The estimate uses a 75% layout factor and cannot inspect structure, shade, orientation, setbacks, wind conditions or exact module dimensions.
Sources and review information
Frequently asked questions
Is the solar roof area calculator free?＋
Yes. SolvePilot tools are free, work in your browser, and require no account.
Does SolvePilot store my values?＋
No. Calculations run locally in your browser and the values you enter are not sent to a server.
Should I treat the result as an exact bill or quotation?＋
No. Results are informed estimates. Final charges can vary because of taxes, tariffs, lender terms, usage patterns, or provider rules.
How can I improve the accuracy?＋
Use recent values from your own bill, statement or institution, review every assumption, and confirm important results with the relevant official source.
Can every clear-looking roof area hold panels?＋
No. Structure, setbacks, water tanks, shade, access paths and wind loading require a site survey.