There are two things to consider:

• Solar Array Wattage
• Solar Array Voltage

To determine the Solar Array Wattage, simply multiple each solar panel's watts by the number of solar panels you have. For example, if you have six 300 Watt solar panels, then your Solar Array Wattage is 1800 Watts.

To determine the maximum number of solar panels you can use with an inverter, take the inverter's maximum input voltage and divide by your solar panel's Open Circuit Voltage (Voc). The Voc can usually be found on a label on the back of your solar panel or on a datasheet.

For example, let's use the SMA SB5.0-1 SP-US-41 Sunny Boy Inverter and let's pretend your solar panel has a Voc of 40. The Sunny Boy SB5.0 has a maximum input voltage of 600V, therefore, the maximum number of solar panels you can use is 15 (600V / 40Voc = 15 solar panels).

To determine the minium number of solar panels you can use with an inverter, take the inverter's minimum input voltage (aka start voltage) and divide by your solar panel's Open Circuit Voltage (Voc).

For example, the SMA SB5.0-1 SP-US-41 Sunny Boy Inverter has a minimum input voltage of 100V in a 208V system or 125V in a 240V system. Pretending that our system is going to be 240V, we need at least 125V to start the inverter, therefore, the minimum number of solar panels you can use is 4 (125V / 40Voc = 3.125 rounded up to 4 solar panels).