Estimate an indicative solar array and panel count from daily energy, sun hours and system losses.
The roof-area allowance is a visible planning assumption, not a sourced site measurement. Use a site-specific shade, orientation, structural and electrical assessment before buying equipment. Trust level: engineering estimate; verify site and equipment assumptions before purchase or installation.
| Assumption | Value |
|---|---|
| Clear roof area planning allowance | 2 m² per panel |
Method: array kW = daily kWh ÷ (peak-sun-hours × (1 − loss))
Inputs used: 12 ÷ (5 × (1 − 20%)) = 3 kW
Assumptions: Clear roof area planning allowance
Scope and warnings: The roof-area allowance is a visible planning assumption, not a sourced site measurement. Use a site-specific shade, orientation, structural and electrical assessment before buying equipment.
National Renewable Energy Laboratory · PVWatts supported locations; use a location-specific model for a site estimate · effective PVWatts version 5 documentation · reviewed 2026-09-12
high confidence · Engineering estimate
Supports the transparent solar energy relationship and system-loss planning reference.
Exclusions: Not a structural, electrical or financing assessment. ToolMitra does not query PVWatts automatically.
The array estimate divides daily energy by peak sun hours and the usable system fraction after losses. Panel count rounds upward from the selected panel rating. This is an early sizing screen, not a yield forecast or installation design.
For 12 kWh per day, 5 peak sun hours and 20% losses, the indicative array is 3 kW. With 550 W panels, that rounds up to six panels before site constraints.
Use a location and orientation-specific solar resource estimate, ideally from a tool such as NREL PVWatts or a local qualified designer. Do not substitute daylight hours: peak sun hours express equivalent full irradiance.
Calculations run on your device. Review your results before exporting or sharing them.
Use average daily consumption from a representative period and a location-specific peak-sun-hours value. The loss assumption should cover temperature, wiring, inverter and mismatch losses without pretending they are identical at every site.
Panel count is rounded upward, while roof area uses a visible planning allowance of 2 m² per panel. A designer still needs dimensions, shade, structure, orientation, local rules, inverter compatibility and grid-connection requirements.
Published by ToolMitra — methods and editorial approach.