When you finally have all the solar power you need, you might discover that you’ve ended up with multiple solar panels. While it may seem like it’s just a matter of connecting lots of wires, this decision is crucial because the wiring of the panels affects the overall performance, efficiency, and complexity of the system. Here, we will describe three common wiring methods: series, parallel, and series-parallel. Each of these comes with its own advantages, disadvantages, ideal use cases, and considerations. It’s best to understand all three so that you can choose the best option for your setup.
Series Connection
Series connection is the most popular configuration for home grid-tie systems. In a series connection, the voltage of the solar panels adds up while the current remains the same as a single panel. This setup is recommended for larger systems, such as one rated at 4 kilowatts or more.
If your inverters are far apart, a series connection is ideal because high-voltage connections reduce power loss along the cables. However, the downside of a series connection is that the entire string performs only as well as its weakest link. For example, if one panel is shaded and its performance drops, all the other panels in the string will also lose efficiency.
How to Do It:
- Connect the positive (+) cable of one panel to the negative (-) cable of the next.
- Note: The female MC4 connector typically marks a positive cable, and the male MC4 connector indicates a negative one.
- Repeat this pattern for all panels.
In the end, the first panel’s positive cable and the last panel’s negative cable will remain free. Use these to connect to your inverter or charge controller.
Parallel Connection
Parallel connection is commonly used for small off-grid systems, such as those in RVs or boats. When panels are wired in parallel, their currents add up while the system’s voltage remains low.
This configuration is great for avoiding the issues associated with series connections. In a parallel setup, each panel operates independently, so if one panel is shaded or malfunctions, it won’t affect the performance of the others. Additionally, the low voltage allows you to use a more affordable PWM controller instead of an expensive MPPT one.
However, wiring panels in parallel requires thick wires capable of carrying high currents. You’ll also need additional components, such as branch connectors and combiner boxes. For larger systems, a parallel configuration can become costly and complicated.
To Connect Solar Panels in Parallel:
- Combine the positive (+) cables from all panels into one and do the same with the negative (-) cables.
- Use branch connectors or a combiner box for this purpose.
- If fuses are needed, place them between the positive cables and the branch connector.
The combined cables from the branch connectors or combiner box typically connect to a charge controller in off-grid systems. For detailed instructions, see our article on parallel connections.
Series vs. Parallel Solar Panels
Which one should you go with? By now, you should be able to answer this question. If your system is large and requires high voltage, a series connection is the best choice. If you have a smaller setup that needs to function well in shaded environments, parallel connections are the way to go.
Series-Parallel Connection
The series-parallel configuration is common in small to medium-sized off-grid systems for RVs, boats, or tiny houses with at least four panels. This setup provides better control over system voltage by creating high-voltage strings of panels and then paralleling those strings to combine their output. Wiring panels in a series-parallel configuration adjusts the system’s voltage and amperage to match your specific needs. This is especially useful if you want to avoid exceeding the maximum input voltage of a charge controller while also keeping the current low enough to avoid requiring thick wires.
This configuration is more complex than the series or parallel setups. There are a couple of key considerations: the system must have an even number of panels, and the strings connected in parallel must be identical. You’ll also need additional components, such as branch connectors or a combiner box.
How to Connect Six Solar Panels in Series-Parallel:
- Connect the positive cable of one panel to the negative cable of the next to form strings (e.g., two strings of three panels or three strings of two panels). Each string will have one loose positive cable and one loose negative cable.
- Use branch connectors or a combiner box to join the loose positive cables and do the same for the negative cables.
- Place fuses between the positive cables and the branch connector if needed (combiner boxes often have built-in fuses).
- Use a multimeter to check the voltage and current before connecting to the charge controller or inverter.
And that’s it! So, for your solar panels, will it be series, parallel, or series-parallel? Hopefully, this blog has helped you make that decision.