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DIY Cost Tools

DIY Cost Tools

Solar Panel Output Calculator

Estimate solar-array energy from panel rating, panel count, peak-sun hours, and total system losses.

Use the units shown beside each field. Decimal and scientific notation are accepted for non-integer fields; blanks, commas, fractions and non-finite entries are rejected.

Array nameplate power4 kW
Estimated daily energy14.4 kWh
Estimated monthly energy438.291 kWh
Estimated annual energy5259.492 kWh

The displayed results apply to the default example. Enable JavaScript to calculate other inputs.

How to use this calculator

  1. Replace the example values with measurements or ratings for the exact vehicle, circuit, component or system.
  2. Keep every value in the labeled unit and use manufacturer data where available.
  3. Select Calculate, then review the result together with the limitations and safety notes.

Formula and method

Array kW = panel watts × count ÷ 1,000. Daily kWh = array kW × peak-sun hours × (1 − loss rate).

Calculations run in your browser. Results are hidden whenever an input changes or validation fails, preventing an older result from being mistaken for a new calculation.

Worked example

Panel rating = 400 W; Number of panels = 10; Average peak-sun hours per day = 4.5 hours; System losses = 20 %. The calculator returns Array nameplate power = 4 kW; Estimated daily energy = 14.4 kWh; Estimated monthly energy = 438.291 kWh; Estimated annual energy = 5259.492 kWh.

The worked example uses the same defaults shown in the interface, allowing the formula and displayed result to be checked together.

Limitations and safety

Shade, orientation, temperature, snow, soiling, inverter clipping, weather and local solar resource affect production. Use site-specific design software for investments.

This is an educational planning model. Confirm ratings, tolerances, code requirements and safe procedures with manufacturers and qualified professionals before purchasing, modifying, wiring or operating equipment.

Frequently asked questions

Are peak-sun hours the same as daylight hours?

No. Peak-sun hours express daily solar energy as equivalent hours at 1,000 W/m², not the number of hours between sunrise and sunset.

Why does the calculator reject my entry?

Each field shows its supported range. Whole-number fields reject decimals, and all fields reject blanks, words, comma-formatted numbers, fractions and non-finite values.

How should I use the displayed precision?

Keep extra digits while checking the calculation, then round to the precision supported by the measurements, component tolerances and published ratings.

Review notes and reference

Reviewed October 4, 2026. The formula and default example were checked together. The script was tested for defaults, input boundaries, invalid formats, condition-specific errors and recovery after an error. Reference: OSHA electrical safe-work requirements. Explanations and examples are original.

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