Solar System Size Calculator
Estimate required system size, panel count, and roof area.
Last updated: 2026-05-16
This calculator uses generic assumptions. Use advanced mode to override them for a more accurate result.
Inputs
Formula transparency
Source: defaultkW = Daily kWh / (Sun hours × Performance Ratio)
Frequently asked
- How do I find my kWh usage?
- From your electricity bill, or enter the bill amount and we'll estimate the kWh.
- What are peak sun hours?
- The daily average of full-irradiance hours. We default to the capital's value.
- Is the result accurate?
- It's a rough estimate. Installation needs an engineering survey of roof, shading, and orientation.
- Why do numbers differ by country?
- Peak sun hours genuinely vary between countries and cities.
- Do you store my data?
- No, the calculation is entirely local.
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Results are estimates and not professional advice. Verify important decisions with a qualified professional.