Module String Design Calculator

Calculate optimal string length based on module Voc, Vmp, temperature coefficients, and inverter MPPT voltage window.

Input Parameters

Results

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Max Modules/String
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Voc at Min Temp
V
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Vmp at Max Temp
V
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Recommended Modules
Note: NEC 690.7 requires string voltage not exceed inverter max input voltage at lowest expected temperature. Use -10°C for most US locations.

Reference

Voc_cold = Voc_STC × [1 + (Tc_Voc/100) × (T_min − 25)] Vmp_hot = Vmp_STC × [1 + (Tc_Voc/100) × (T_hot − 25)] Max Modules = floor(MPPT_max / Voc_cold) Recommended = floor(0.95 × MPPT_max / Voc_cold)