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Lots of solar power means lots of PV modules. How to wire solar panels? There are several options. In this article, we’ll talk about how to connect solar panels together, look at three wiring methods and explain which one is the best for you.
Key takeaways
When planning your solar panel system, the way you connect solar panels together can make a big difference in how well they perform. Let's explore the key factors that will help you make the right choice.
Solar panel system size is generally the main consideration. The number of solar panels in your system affects how you should wire them together. Smaller systems with just a few panels often work well with a simple series connection, like a string of holiday lights. But larger systems might need a combination of series and parallel connections to handle the higher power output and maintain stable voltage levels.
7 kW — average size of a home solar system in the US
How far your panels sit from the inverter matters because electricity loses some power as it travels through wires. Series connections are usually a better option for longer distances because they operate at higher voltages, which means less power loss along the way. For shorter ranges, parallel connections can work just fine since power loss is less of a concern. The larger distance with the parallel connection means the cable gauge has to increase.
Trees, chimneys, or nearby buildings that cast shadows on your panels should influence your wiring choice. When panels are connected in series, shade on one panel can significantly reduce the output of the entire string - like one bad bulb affecting a whole string of Christmas lights. Parallel connections are more forgiving with shade since each panel operates more independently.
Every inverter has specific voltage and current requirements that your wiring setup must match. String inverters typically need higher voltages, making series connections a natural fit. Microinverters and power optimizers, on the other hand, work with individual panels or small groups, making parallel connections more practical. Always check your inverter's specifications before deciding on a wiring configuration.
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Get quotesBefore diving into solar panel connections, it's essential to understand the basic electrical concepts that make your PV system work. Think of these as the panel wiring basics that help you make informed decisions about your setup.
Before you begin wiring your solar panels, having the right equipment on hand is crucial for a safe and successful installing of solar panels. Let's look at everything you'll need — besides correct information.
A quality digital multimeter is your most important tool - it helps you verify proper voltage and current readings at each step. You'll also need wire strippers that can handle different gauges of wire, and an MC4 connector crimping tool for making secure connections. A set of screwdrivers and wrenches will help with mounting hardware, and cable ties or conduit straps will keep your wiring neat and secure.
Your main electrical components will include MC4 connectors, which are the industry standard for solar panel connections. You'll need solar-specific cables rated for outdoor use and UV resistance - usually in red for positive and black for negative connections. For parallel configurations, you'll also need branch connectors or a combiner box. Make sure to choose cables with the proper thickness (gauge) based on your system's current requirements.
Working with electrical systems requires proper safety gear. Insulated gloves rated for the voltage you're working with are essential. Safety glasses protect your eyes from accidental sparks or debris. If you're working on a roof, you'll need fall protection equipment including a safety harness and secure anchor points. Keep rubber-soled shoes handy for electrical insulation, and always have a first aid kit and fire extinguisher nearby in case of emergencies.
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Series connection is the most popular configuration for home grid-tie systems: cheap and offers good efficiency. When you connect solar panels in series, their voltages add up. The current is as low as a single panel in an array provides.
Maximum power point technology in an inverter allows it to convert extra voltage to current. Some inverters have multiple power point trackers.
Pros and cons: For large systems that are over, say, 4 kilowatts, the series connection is the most natural choice. Series connection is also great when solar panels and the inverter are far away from each other. High voltage connection reduces power loss along the cables.
The biggest enemy of solar panels wired in series is shading. In a string, solar panels depend on each other. The entire series string performs as well as its weakest link, therefore when one panel gets shaded, then the performance of others drops as well.
How to connect multiple solar panels together in series: Connect the positive (+) cable of one panel to the negative (-) one of the next panel. The female MC4 connector marks a positive cable and the male MC4 is the negative. Continue with the rest until all panels are connected. The positive cable of the first panel and the negative one of the last panel remain loose so you can connect them to the DC terminal of the inverter or charge controller. Connect a negative cable to a negative terminal and a positive terminal to a positive terminal. Check out our article on series connection with step-by-step instructions.
Color code your wires! Positive cable is usually red and the negative should be black. If your cables aren’t colored, mark them using duct tape
Parallel connection is common in small off-grid systems, such as RV and boat systems. With panels wired in parallel, their currents add up while the voltage in the system remains low.
Pros and cons: In this configuration, solar panels are independent of one another. When one panel is shaded or malfunctions, it doesn’t affect the performance of others. Since the voltage in a system is low, you can often add a cheap PWM controller instead of a more expensive MPPT one.
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Wiring panels in parallel requires thick wires that can carry high currents. You’ll also need addons, such as branch connectors and combiner boxes. In a large system, using parallel configuration becomes costly and complicated because the cable gauge increases greatly.
How to connect solar panels together in parallel: Join the positive (+) cables of all the panels into a single one, then do the same with all the negative (-) cables. For this, you will need branch connectors or a combiner box. If the array needs fuses, add them in between the positive cables from panels and a branch connector. Branch connectors or cables from the combiner box usually go into a charge controller in an off-grid system. Make sure to connect matching terminals. From there, direct current generally goes into an DC-to-AC inverter or a battery. Check out our article on parallel connection with step-by-step instructions.
Series-parallel connection is common in small to medium-sized off-grid systems for RVs, boats or tiny houses where there are at least four panels. This configuration gives you more control over voltage in the system. For example, you can create two strings of panels with high voltage but then wire them in parallel to combine their amperage. It’s the most complicated solar design.
Pros and cons: Wiring panels in series parallel is adjusting volts and amperes in the system to your needs. For example, it can be good if you don’t want to exceed the maximum input voltage of a charge controller and at the same time don’t want to have too much current so that the system requires a thick wire.
The configuration is more complicated than a simple series or parallel connection. The number of panels in a system has to be even. The strings that you want to wire in parallel have to match. You’ll require addons such as branch connectors or a combiner box.
How to connect solar panels in series-parallel: Let’s say you wonder how to connect six solar panels together. There are two ways: you could create two strings with three panels in each or three strings with two panels in each.
First wire solar panels in series. Each string will have a loose positive cable and a loose negative cable. Then join the loose negative cables from strings together and positive ones with branch connectors or a combiner box. If the array needs fuses, add them in between the positive cables from strings and a branch connector. A combiner box usually has built-in fuses. Use a multimeter to check volts and amperes in the system.
Taking care of your solar panel connections ensures they'll keep producing power efficiently for years to come. Let's look at common problems you might encounter and how to prevent them.
Low power output often results from dirty panels or loose connections. If you notice a significant drop in performance, first check if your panels need cleaning. Next, inspect all MC4 connectors - they should be fully clicked together and show no signs of corrosion or damage. If only part of your array is underperforming, you might have a shading issue or a faulty panel in a series string.
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Inconsistent voltage readings usually point to connection problems. Using your multimeter, test the voltage at each connection point. In series configurations, a sudden voltage drop between two points indicates a problem with that connection or panel. Hot spots on cables or connectors are serious warning signs - they indicate high resistance in the connection, which can be dangerous if not addressed promptly.
Regular maintenance tips
When it comes to wiring solar panels together, there's no one-size-fits-all solution. Your choice between series, parallel, or series-parallel connections should be based on several key factors: the size of your system, the distance to your inverter, local shading conditions, and your inverter's specific requirements. Series connections excel in larger home installations where high voltage is needed, while parallel setups shine in smaller systems where shade might be an issue.
The good news is that each wiring method has clear strengths that make it suitable for specific situations. Series connections offer efficient power transmission over longer distances, parallel connections provide better performance in partially shaded conditions, and series-parallel arrangements give you the flexibility to balance both worlds. By carefully considering your specific needs and circumstances, you can choose the wiring configuration that will help your solar panel installation perform at its best for years to come.
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Andrey had been a news editor and freelance writer for a number of medias before joining A1 SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.
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