Solar Panel Calculator
Estimate solar-array size and panel count from energy use, peak sun hours and system losses
Required array size
How we calculated it
About the Solar Panel Calculator
Solar Panel Calculator estimates energy production from panel power, sunlight availability and system losses, or estimates the panel capacity needed for a target energy load. It is useful for early-stage sizing of small solar systems.
Rated panel watts are measured under standard test conditions. Real output changes with irradiance, temperature, orientation, shading, wiring and inverter efficiency.
How to Use the Solar Panel Calculator
- Enter total panel rated power or the target daily energy need.
- Enter expected peak-sun-hours for the site and season.
- Enter a system-efficiency or loss factor when supported.
- Calculate daily energy or required array size and test a lower-sun scenario before finalizing a design.
How the Calculation Works
Estimated daily energy = array power in kW × peak-sun-hours × system efficiency.
To size an array from energy demand, required array kW = daily energy need ÷ (peak-sun-hours × system efficiency).
Worked example
Solar Panel Calculator Worked Example
2 kW array, 5 peak-sun-hours, 80% system efficiency
Estimated daily energy = 2×5×0.80 = 8 kWh per day under the modeled conditions.
Result guide
Understanding Your Solar Panel Calculator Result
The result is an average-energy scenario, not guaranteed daily production. Cloud cover and seasonal solar variation can create much lower output on individual days.
Before you rely on the answer
Assumptions and Limitations
- Peak-sun-hours are representative of the site and period.
- System efficiency reflects major real losses.
- Shading and orientation are captured in the assumptions or handled separately.
Practical tip
Using This Result in Practice
For off-grid systems, size around the difficult season rather than the annual average. Battery capacity and consecutive cloudy days can matter more than a strong average solar month.
Related calculations
Useful Calculations to Continue With
If you want a more direct panel-output estimate from system inputs, use the Solar Panel Output Calculator.
If the solar array charges storage, use the Battery Capacity Calculator to size the energy reserve separately.
Common questions
Solar Panel Calculator FAQ
What are peak sun hours?
An equivalent number of hours per day at 1,000 W/m² solar irradiance, used to summarize available solar energy.
Why does a 400 W panel not always produce 400 W?
Rated power is measured under test conditions; real irradiance, temperature and system losses change output.
Can this calculator size an off-grid system completely?
No. Battery storage, inverter limits, surge loads, shading and seasonal weather also need to be considered.