Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Simplified energy balance. No location-specific irradiance, seasonal adequacy, battery sizing or structural/electrical design.
Example Calculation
- Daily energy target: 10 kWh/day
- Peak-sun hours: 4 h/day
- Overall performance factor: 80 %
- Panel rating: 400 W
10 kWh/day with four peak-sun hours and an 80% performance factor needs 3.125 kW, rounded to eight 400 W panels.
Frequently asked questions
How do I use this calculator?
Enter daily energy target, peak-sun hours, overall performance factor, panel rating. The result updates automatically. Use Reset to restore the example values.
What method does it use?
required kW=target/(sun hours × performance); panel count=ceil(kW ×1000/panel watts).. Simplified energy balance. No location-specific irradiance, seasonal adequacy, battery sizing or structural/electrical design.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.