The decision to connect solar panels in series or parallel depends on the specific requirements of your solar PV (photovoltaic) system, the characteristics of the solar panels, and the components used in the system.

1. Voltage Requirements:

• Series Connection: When the system requires a higher voltage to match the inverter or charge controller specifications. In a series connection, the voltages of individual panels add up.
• Parallel Connection: When the system needs to maintain a specific voltage but requires an increase in current. In parallel, the voltage remains the same, but the current adds up.

2. Inverter or Charge Controller Specifications:

• Check the voltage and current requirements of your inverter or charge controller. Connect the solar panels in a way that the combined voltage and current fall within the acceptable range specified by the system components.

3. Shading Considerations:

• Series Connection: More susceptible to shading issues. If one panel in a series is shaded, it can affect the performance of the entire string. Consider using bypass diodes to mitigate shading impacts.
• Parallel Connection: Panels operate independently, so shading on one panel has a localized effect, minimizing the impact on the entire array.

4. System Design and Configuration:

• Consider the overall design and configuration of your solar PV system. Determine whether your system benefits more from higher voltage, higher current, or a balance of both.

5. Wire Size and Voltage Drop:

• Series Connection: Requires a higher voltage but lower current, which can reduce the size and cost of wiring. However, voltage drop over long wire runs can be a consideration.
• Parallel Connection: Higher current, which may require larger wire sizes. However, voltage drop is less of a concern.

6. Module Mismatch:

• Consider the mismatch in power output among solar panels. If panels in a series are mismatched, the overall performance is limited by the lowest-performing panel. Parallel connections can be more tolerant of module mismatch.

7. Maintenance and Monitoring:

• Parallel Connection: Easier to monitor and maintain because each panel operates independently. A fault in one panel does not affect the others.
• Series Connection: If one panel fails or is shaded, it can impact the performance of the entire string.

8. System Efficiency:

• Consider the overall efficiency of your system. The choice between series and parallel connections can affect the overall efficiency of energy production, and it depends on the specific requirements and conditions of your installation.

9. Safety:

• Ensure safety by following local electrical codes and standards. Properly install and ground the solar panels, and use appropriate components to prevent electrical hazards.

10. Combination of Series and Parallel:

• In some cases, a combination of series and parallel connections, known as a series-parallel configuration, may be used to balance the benefits of both approaches.

Ultimately, the choice between series and parallel connection or a combination of both depends on the specific characteristics of your solar panels, system requirements, and the constraints of your installation. It’s advisable to consult with a solar professional or engineer to ensure the optimal design and configuration for your particular situation.