Definition
Vmp (Maximum Power Voltage) is the voltage at which a PV module produces its maximum power, measured at STC. Typically 0.78–0.85 × Voc. Critical for ensuring string voltage stays above the inverter MPPT minimum at hot operating temperature.
Vmp Behavior
Vmp(T) = Vmp(STC) × [1 + β_Vmp × (T_cell − 25)]At T_cell = 65°C with β_Vmp = −0.003/°C: Vmp drops 12% from STC.
String Sizing Constraint
N_min = ceil(Vmppt_min / Vmp(T_hot))Key Takeaways
- Vmp = voltage at maximum power point, at STC.
- Decreases with rising cell temperature.
- Hot-day Vmp must stay above inverter MPPT minimum.
- Determines the minimum string length in series.
- Datasheet provides Vmp(STC); design must temperature-correct.
Frequently Asked Questions
4 commonly searched questions about Vmp (Maximum Power Voltage).
What is Vmp?
Maximum Power Voltage — the voltage at the maximum power point on a module's I-V curve. Reported at STC on the datasheet.
Typical Vmp?
60-cell mono: 32–36 V. 72-cell mono: 38–42 V. 144-cell half-cell: 39–42 V. Bifacial similar to monofacial.
How does Vmp change with temperature?
Decreases with rising cell temperature. β_Vmp typically −0.30 to −0.40 %/°C. At 65°C cell temp, Vmp drops ~12% from STC value.
Why is Vmp critical for string sizing?
String Vmp at hot temperature must stay above inverter MPPT minimum. Vmp(T) = Vmp(STC) × [1 + β_Vmp × (T − 25)] determines minimum string length.
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