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Science & Engineering

Solar Panel Output Estimator

Estimate daily, monthly and yearly solar PV output from panel ratings, peak sun hours and system losses.

Your inputs

Look up your site’s average solar irradiance (kWh/m²/day) from a solar resource map.

14 % is the default used by NREL’s PVWatts model (wiring, soiling, inverter, mismatch …).

Results

Average daily output

15.48 kWh

Average monthly output
471.2 kWh
Yearly output
5,650 kWh
System size
4 kWp
Yearly value at your price
$847.53

≈Estimate based on the stated model and assumptions

Notes for this result

  • Output varies with season, weather, shading, tilt and orientation. For a site-specific estimate use a model such as PVWatts.

What this calculator does

A PV system’s energy depends on its size, the sunlight at your site and real-world losses.

Formula and method

Daily kWh = (panel W × panels ÷ 1000) × peak sun hours × (1 − losses)

Worked example

Calculated by this tool with its default inputs:

Inputs

  • Panel rating: 400 W
  • Number of panels: 10
  • Peak sun hours per day (your location): 4.5
  • System losses: 14 %
  • Electricity price per kWh (optional): 0.15 (any currency)

Results

  • Average daily output: 15.48 kWh
  • Average monthly output: 471.2 kWh
  • Yearly output: 5,650 kWh
  • System size: 4 kWp
  • Yearly value at your price: 847.53

How to read the results

Peak sun hours equal the average daily solar irradiation in kWh/m².

Assumptions and limitations

  • The 14 % default loss is the value used by NREL’s PVWatts calculator.
  • Seasonal variation can be large.

These are educational estimates. Electrical, structural and other safety-critical work must comply with local codes and be designed or checked by a qualified professional.

Questions

What are peak sun hours?

The equivalent number of hours per day at 1000 W/m² of sunlight.

Sources

Methodology and verification

Result type
Estimate based on the stated model and assumptions
Formula version
1.0
Automated verification
3 reference and validation test cases, checked against independently computed values. The site cannot be built if any of them fail.
Editorial review
Awaiting human editorial review. The explanation was drafted with AI assistance; the formula and examples are verified by the automated tests above.

Privacy

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