Zerdly

Solar Output Calculator

Estimate daily and monthly solar panel energy output from system size, sunlight hours and efficiency, free right in your browser.

100% FreeRuns in your browserBasic
How to use this calculator

Enter Values

Minimum 0

Minimum 0

Range 0–100

Enter your values and press Calculate to see results.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter the system size in watts and the peak sun hours for your area.
  2. Optionally set efficiency, then Calculate.

How it works

Daily energy = system size (W) × peak sun hours × efficiency, divided by 1000 for kWh. Efficiency (default 75%) covers inverter, wiring, temperature and dirt losses.

Worked example

400 W, 5 sun hours, 75%. 400 × 5 × 0.75 ÷ 1000 = 1.5 kWh a day.

Common mistakes

  • Using nameplate kW as daily output — multiply by sun-hours and a system-loss factor of about 0.78.
  • Ignoring orientation and shading, which can cut output sharply.

Frequently asked questions

How much energy will my solar system produce?

Daily kWh ≈ system kW × peak sun-hours × performance ratio (~0.78). A 6.6 kW system at 4.5 sun-hours makes roughly 23 kWh a day.

What are peak sun-hours?

The hours per day equivalent to full 1,000 W/m² sun — typically 3.5–5.5 across much of Australia, varying by location and season.

What are peak sun hours?

The number of hours per day equivalent to full 1,000 W/m² sunshine. It varies by location and season — 3–6 is typical — and isn't the same as daylight hours.

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Cite this tool

Zerdly. (2026). Solar Output Calculator. Retrieved from https://www.zerdly.com/tools/solar-output-calculator/

Tip: Enter any known values to calculate the remaining results.

All calculations run in your browser. Your inputs are never saved or transmitted.