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Solar string calculator: panels per string for EG4 inverters

Check how many of your panels can share one string on an EG4 inverter, including the voltage rise on the coldest day.

Last updated Sep 3, 2026

A row of solar panels in a frosty field at sunrise.

Solar panels make more voltage in the cold, and an inverter’s voltage limit is a hard limit: go over it and the unit can be damaged, which several EG4 datasheets say the warranty does not cover. This calculator tells you how many of your panels can go on one string.

  1. Pick the inverter
  2. Copy three numbers from your panel’s datasheet
  3. Enter your coldest temperature
Try an example
1. Inverter or MPPT
2. Your panel (see its datasheet)
3. Your climate

Use the lowest temperature you have seen or your local climate record; we do not ship a table of guesses.

How it is calculated

  • Coldest-day voltage per panel = Voc × (1 + temperature coefficient × (coldest temperature − 25 °C)).
  • Maximum panels = the inverter’s voltage limit ÷ that figure, rounded down. The limit is the datasheet’s planning figure: the “MPPT voltage high protection” value (550 V on the 18kPV, 12kPV and FlexBOSS models, where the unit faults) or the DC input range top (480 V on the 12000XP and 6000XP), not the higher absolute maximum.
  • Also capped by the top of the MPPT operating range ÷ Vmp, where the datasheet lists one, and minimum panels by the bottom of that range ÷ Vmp.

The inverter numbers are datasheet values shown on each model page. The panel numbers and the coldest temperature are yours; the examples use a made-up panel for illustration only. EG4 also publishes its own string sizer, linked from its datasheets: use it to confirm before you buy. Background: what an MPPT is and how cold changes batteries and panels.