PV string voltage equations
Cold temperature raises module open-circuit voltage while hot temperature lowers operating voltage.
V(T) = VSTC × [1 + β × (T − 25°C)]Nmax = floor(VDC,max / Voc,cold)Nmin = ceil(VMPPT,min / Vmpp,hot)where:
- β
- Module voltage temperature coefficient[/°C]
- N
- Modules connected in series
- Voc
- Module open-circuit voltage[V]
- Vmpp
- Module maximum-power voltage[V]
Both the inverter absolute maximum and MPPT window must be satisfied.
How to use the PV String Sizing Calculator
Calculate temperature-corrected PV string voltage and the allowable module count for an inverter MPPT window. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Entered temperatures are conservative cell temperatures Linear datasheet coefficients around STC A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Entered temperatures are conservative cell temperatures
- Linear datasheet coefficients around STC
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Use the inverter's absolute maximum voltage separately from its MPPT operating window. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Entered temperatures are conservative cell temperatures
- Linear datasheet coefficients around STC
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.
- Use the inverter's absolute maximum voltage separately from its MPPT operating window.