Solar Panel String Calculator - V1.2

Solar Panel String Calculator

Calculate optimal panels per string with winter derating & voltage limits

How to Size Your Solar String Correctly

What is Winter Derating in Solar?

Winter derating accounts for reduced solar irradiance and temperature effects during colder months. Panels typically produce 10-25% less than STC ratings in winter conditions.

Why Does System Efficiency Matter?

System efficiency covers losses from inverters, wiring, soiling, and mismatch. Most residential systems operate at 95-98% efficiency under optimal conditions.

Understanding Max DC Voltage Limits

Every inverter has a maximum DC input voltage. Exceeding this can cause permanent damage. Always check your inverter datasheet before designing strings.

What is Panel Voc and Temperature Coefficient?

Voc (Open Circuit Voltage) increases in cold weather. A standard 49.5V panel can reach 55V+ on cold sunny mornings, pushing string voltages higher than expected.

How to Calculate Panels Per String

Divide inverter Max DC Voltage by panel Voc to get maximum panels. Then verify against power requirements and winter derating to ensure performance.

State-Based Solar Performance Factors

Solar irradiance varies by location. TAS and VIC need higher derating than QLD or WA. Always factor local climate when calculating array sizes.

Common String Sizing Mistakes to Avoid

Don't ignore cold-weather voltage rise. Don't oversize beyond MPPT range. Don't forget to check minimum startup voltage for early morning generation.

© 2026 Solar Design Tools. Calculations are estimates only. Consult AS/NZS 5033 and qualified installers.