Solar Panel Size Calculator
Estimate solar-array wattage from daily energy demand, peak sun hours, efficiency and recharge target.
Estimate solar-array wattage from daily energy demand, peak sun hours, efficiency and recharge target.
Estimate solar-array wattage from daily energy demand, peak sun hours, efficiency and recharge target.
Enter your own equipment values. The calculator uses transparent assumptions so you can adjust efficiency, reserve and operating conditions.
Use Real Equipment Ratings
Estimate solar-array wattage from daily energy demand, peak sun hours, efficiency and recharge target.
Calculator Guidance
Use the result for planning, then verify the exact product manual, nameplate ratings and operating limits.
Solar Panel Size Calculator
Planning estimate only.
Formula
Panel watts = daily Wh ÷ recharge days ÷ peak sun hours ÷ system efficiency.
Examples
| Daily Energy | Sun Hours | Efficiency | Panel Target |
|---|---|---|---|
| 1000Wh | 5 | 75% | 267W |
| 2000Wh | 4 | 75% | 667W |
| 5000Wh | 5 | 80% | 1250W |
Important Limits
Weather Variability
Clouds reduce harvest.
Panel Temperature
Heat lowers output.
Charge Controller
Voltage and current limits apply.
Shading
Partial shade can cut output sharply.
Season
Winter sun hours may be much lower.
Battery Acceptance
Charging can taper near full.
How to Use the Result in the Real World
Treat the calculated result as a planning baseline rather than an exact promise. Real systems lose energy through conversion, wiring, temperature effects and internal electronics, while appliances can draw differently from their nameplate ratings.
Leave practical headroom instead of selecting equipment that exactly matches the result. Extra margin helps with startup surges, battery aging, changing weather and future loads, and it reduces the chance that normal variation pushes the system beyond its limits.
When the result affects a major purchase, verify the important inputs. Measure appliance consumption when possible, check the exact inverter or charge-controller limits, and compare the calculation with the equipment manufacturer's specifications.
Frequently Asked Questions
What efficiency should I use?
About 70–80% is a practical planning range.
What are peak sun hours?
Equivalent hours of 1000W/m² solar irradiance.
Should I size for winter?
Yes if year-round reliability matters.
Can panel wattage exceed controller input?
No.
Why add extra panel capacity?
Weather and seasonal losses.
Does orientation matter?
Yes.