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PV String Sizing

Min/max modules per string against inverter MPPT and DC voltage.

Electrical

Core inputs only — quick sizing with engineering defaults.

Inputs (SI units)

Module Voc (STC)V

Module Vmp (STC)V

Voc temp coeff β%/°C

Negative values are not allowed

Vmp temp coeff γ%/°C

Negative values are not allowed

Lowest cell temp°C

Highest cell temp°C

Inverter MPPT lowV

Inverter MPPT highV

System max DC voltageV

Results

Fix input errors to compute results.

Save & Load Project

Designs are stored privately in this browser — nothing is uploaded.

Engineering Formula

V_oc(T_min) = Voc × [1 + β/100 × (T_min − 25)]
V_mp(T_max) = Vmp × [1 + γ/100 × (T_max − 25)]
N_max = ⌊V_max / Voc(T_min)⌋
N_min = ⌈V_MPPT_low / Vmp(T_max)⌉

Cold mornings push Voc up (β negative → higher V at low T); hot afternoons pull Vmp down. Both boundaries must lie inside inverter limits per IEC 62548.

Design Assumptions

• Cell temp ≈ ambient at Voc check (dawn).
• Ambient uses site's record low and NOCT-adjusted high.

Engineering Tips

◆Use module cold-temp Voc from datasheet if provided.
◆Fill entire MPPT window for best MPPT tracking accuracy.

Warnings

▲Exceeding V_max destroys inverters and voids UL/IEC listing.

Standards & References

IEC 62548 §7NEC 690.7UL 1741

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