We installed a solar panel array at our house. The total output of the solar panels is around 465 V DC with open circuit. the DC Input limit of the solar inverter is 450 V DC.

I want to lower the incoming voltage from the solar panels to the solar inverter by around 10 V so the inverter can actually work without displaying an error message the whole time.

I need as much wattage as I can, so removing 1 solar panel is not an option. The current that would be passing through is around 19-23 A max.

  • \$\begingroup\$ " the DC Input limit of the solar inverter is 450V DC." - What make and model is your inverter? \$\endgroup\$ Sep 20, 2021 at 4:34
  • 1
    \$\begingroup\$ Sounds like a bad design to begin with. Chose a more suitable inverter. You’ve got to ask yourself if working around a bad design is faster/better/cheaper than just getting the right equipment? \$\endgroup\$
    – Kartman
    Sep 20, 2021 at 10:31
  • \$\begingroup\$ A really beefy 10 V Zener diode in series? Preferably with an array of 12 V light bulbs in parallel. \$\endgroup\$
    – winny
    Sep 20, 2021 at 11:05
  • \$\begingroup\$ Or remove one panel. Keep it as a spare or use it (via suitable charge controller) for charging car/RV/boat batteries. \$\endgroup\$
    – user16324
    Sep 20, 2021 at 12:39

3 Answers 3


Do two strings in series of half the panels connected to the inverter in parallel.

This will reduce the voltage to about 230V.

  • \$\begingroup\$ This piqued my curiosity and I spent an hour or so studying whether this approach was acceptable or even safe. I found nothing to fault it, it's apparently a common solution, although it's mostly individual PV cells connected in parallel, not strings of series connected cells in parallel with each other. @SolarMike, please elaborate, or provide some links to support the claim, because this answer deserves to be less hand-wavy. \$\endgroup\$ Sep 20, 2021 at 13:42

If Voc is 465v then Vmp will be no more than 420V and probably under 400V. What you need is something to load the panels down to say 440 V or about 25V drop. Even if IMAX of 23A was dissipated you'd have 25 X 23 or about 600 Watts dissipation. In practice the current required to load the panels down about 25V from Voc will be usefully less than that.

A simple solution that does not waste energy in normal operation is a resistive load that is switched in when the voltage is too high and switched out when the inverter operates and voltage drops. This could be eg a comparator driving a MOSFET and a resistor of about R = V/I = 450/15 = 30 ohms.

The high voltage and current may make an IGBT better than a FET, and if this only operate when the inverter is off load then a suitably rated contactor may be better.

If this approach is attractive more information can be provided.


Assuming that the present configuration of solar cells cannot be changed, there are two options to reduce the voltage.

  1. NOT RECOMMENDED. Dropping the voltage using resistors/diodes 10V*20A = 200W. Note that the drop-out will change depending on the total current (dependent on lighting conditions)
  2. Using a buck converter to step-down the voltage, very costly affair but provides better efficiency. If you are brave, you may try building a buck converter yourself with this power rating

As @Solar Mike suggested, changing the array configuration is the most efficient way for your application


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