Solar system size calculator
Estimate recommended kW, panel count, generation, roof area, and cost.
Updated 2026-07-15 · Formula version is shown with every result.
Data confidence
Early estimate
Evidence used
Uses monthly electricity use, target offset, panel wattage, and a planning production yield.
What can vary
Site-specific solar resource, shade, roof geometry, inverter choice, and utility rules can change size.
Your inputs
Use realistic values. Nothing is sent to an ad network.
Your estimate will appear here
Results include ranges, supporting metrics, formula version, assumptions, and warnings.
How this estimate works
SolarGabay uses pure, versioned TypeScript formula modules. The calculator normalizes inputs, rejects invalid values, and presents planning ranges instead of false precision.
Results are decision-support estimates. Confirm utility rates, supplier specifications, site conditions, and professional requirements before committing money. Review the methodology and source policy before treating any estimate as decision-ready.