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Solar panel calculator

Estimate daily energy = rated array kW × equivalent peak-sun hours × retained fraction.

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Estimate daily energy = rated array kW × equivalent peak-sun hours × retained fraction.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
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    Formula and assumptions
    Sun hours mean equivalent full-irradiance hours, not daylight length. Site irradiation and loss allowance are your inputs; no weather, shade, orientation or seasonal dataset is assumed. This is not an electrical or roof design.
    Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
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    Using Solar panel calculator
    Estimate daily energy = rated array kW × equivalent peak-sun hours × retained fraction.
    Sun hours mean equivalent full-irradiance hours, not daylight length. Site irradiation and loss allowance are your inputs; no weather, shade, orientation or seasonal dataset is assumed. This is not an electrical or roof design.
    Next: Electricity cost calculator
    A worked example
    Example inputs: panel rating (w) = 400, panel count = 10, site equivalent peak-sun hours per day = 4, energy retained after losses (%) = 80. Modeled daily energy (kWh) = 12.8.
    Before you use the result
    Sun hours mean equivalent full-irradiance hours, not daylight length. Site irradiation and loss allowance are your inputs; no weather, shade, orientation or seasonal dataset is assumed. This is not an electrical or roof design.
    Example results for panel rating (w)
    These examples use Panel count: 10; Site equivalent peak-sun hours per day: 4; Energy retained after losses (%): 80. They are reference calculations, not recommended settings.
    Panel rating (W)Modeled daily energy (kWh)
    2006.4
    40012.8
    80025.6
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    ToolOctopus. “Solar panel calculator.” Updated 2026-09-26. https://tooloctopus.com/solar-panel-calculator.
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