Horisun Solar Stringing Tool

Project Location

Enter ZIP Code (USA)

T_add — Module Temperature Adder (°C)

Added to T_high for Vmp_min calculation per NEC 690.7 guidance.

T_STC Standard Test Condition (°C)

PV Module Specifications

V_oc (V) — Open Circuit Voltage

V_mp (V) — Max Power Voltage

I_sc (A) — Short Circuit Current

I_mp (A) — Max Power Current

V_oc Temp Coeff (%/°C)

Negative value (e.g. -0.27)

V_mp Temp Coeff (%/°C)

Negative value (e.g. -0.35)

P_max (W) — Rated Power

Module Dimensions (optional)

Inverter / String Inverter Specifications

Max DC Input Voltage (V)

Start / Startup Voltage (V)

MPPT Voltage Min (V)

MPPT Voltage Max (V)

Max DC Input Current (A)

Max Short-Circuit Input (A)

Number of MPPT Inputs

Inverter AC Output Power (kW)

Max Strings per MPPT

DC/AC Ratio Target

Formula Reference

Voc_max = Voc × [1 + (Tlow – TSTC) × (Voc_Coef / 100)]
Vmp_min = Vmp × [1 + ((Thigh + Tadd – TSTC) × (Vmp_Coef / 100))]
Vmp_max = Vmp × [1 + (Tlow – TSTC) × (Vmp_Coef / 100)]

Max modules (safety) = ⌊ Inv_Vmax / Voc_max ⌋
Max modules (MPPT hi) = ⌊ MPPT_Vmax / Vmp_max ⌋
Min modules (MPPT lo) = ⌈ MPPT_Vmin / Vmp_min ⌉