String Configuration

Minimum modules per string

Vmin, or MPP Vmin (whichever is smaller). The minimum number of panels required to reach the inverter’s minimum input voltage. Not all datasheets list this value, so if it is not stated, then the MPPT minimum voltage is used

Arrow

Startup voltage. The minimum panels required to reach the inverter’s Startup Voltage. If the number of panels in the string is lower than this, then the inverter may start later in the morning, compared with a longer string.

Lower end of the green

MPP Vmin, or Vmin for Pnom, whichever is greater. The minimum panels required to reach the inverter’s minimum voltage input for the nominal power rating, aka Minimum Voltage for Pnom, or Minimum MPP Voltage for Pnom. Not all datasheets list this value, and it is sometimes only published in the installation instructions. If it is not listed on the datasheet, then the Minimum MPP Voltage is used instead.

Max modules per string

Voc max. The maximum number of panels allowed within all the following limits:

• the inverter’s maximum DC input voltage (Voc)
• regulatory system voltage limits 
  • 1500V for commercial
  • 600/100V for residential (can be set in Admin > My Business > Design & RoI preferences > Limit residential string voltage to 600V)

Higher end of the green

Voc max 3% safety margin. Many module manufacturers state that the Voc may be 3% than STC datasheet values. If the maximum number of modules per string shown is within 3% of the max string voltage limits above, then the line to the last module in the list will be coloured orange to show that it is outside this safety limit.

All Voc and Vmp calculations take into consideration the site temperature.