In this tutorial, I’ll show you how to wire solar panels in series and how to wire them in parallel.
Once we’ve got that covered, I’ll also explain the difference between these two configurations in Voltage (Volts) and Current (Amps) and provide a real-life example.
Finally, I’ll discuss the pros and cons of each configuration to help you figure out which one fits your needs best.
Let’s dive in.
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How to wire solar panels in series and in parallel?
Every solar panel typically comes with a female and a male MC4 connector. Usually, the female MC4 connector stands for the negative terminal, and the male MC4 connector represents the positive terminal of the solar panel. However, keep in mind that this standard isn’t always consistent.
Regardless, the first crucial step before making any connections is identifying the positive and negative wires of your solar panels.
You can usually find polarity indicators somewhere on the solar panel itself. Look for a “+” sign, which indicates the positive wire, and a “-” sign for the negative wire.
These polarity markers can be located on the junction box, the wires, or the MC4 connectors.
If the manufacturer hasn’t clearly labeled the polarity of the solar panel, another approach is to use a multimeter to measure voltage.
To do this, insert one multimeter probe into each of the MC4 terminals.
If the reading shows a positive voltage value, it means the positive (red) probe is connected to the positive end of the solar panel. If the voltage value is negative, then the red probe is connected to the negative end of the panel.
For instance, in the image above, you can observe the red probe inserted into the male MC4 connector of the solar panel, signifying the positive terminal. As a result, my multimeter displays a positive voltage reading.
After identifying the positive and negative wires of your solar panels, be sure to mark them before proceeding.
Now, let’s kick off with the series configuration.
How to wire solar panels in series?
To wire your solar panels in series, simply link the positive MC4 connector of the first solar panel to the negative MC4 connector of the next one, and continue this pattern for the remaining panels.
Once you’re finished, you’ll have two unconnected terminals at each end of your series—a positive and a negative. These can be connected to the solar charge controller using extension cables.
The great thing about connecting solar panels in series is that you won’t need any extra components; all you require are your solar panels and a pair of extension cables to link the solar string to the solar charge controller.
Each of these extension cables comes with an MC4 connector on one end, which attaches to the solar panels, and a stripped end that connects to one of the terminals on the solar charge controller.
As an illustration, for this tutorial, I’ve connected the positive MC4 connector of the left panel to the negative MC4 connector of the right panel since I’m working with only two solar panels.
And voila! we have a string of 2 solar panels:
To hook up the solar panels to the solar charge controller, I simply used the extension cables. I connected the negative end of the string (on the left) to the negative terminal of the SCC and linked the positive end of the string (on the right) to the positive terminal of the charge controller.
How to wire solar panels in parallel?
To wire solar panels in parallel, you’ll require a couple of branch connectors. These connectors link all the positive terminals of the solar panels, creating the positive terminal of the solar array, and they connect all the negative terminals to form the negative terminal of the solar array.
In addition to your solar panels and extension cables, you’ll need two extra components:
- A pair of MC4 Y branch connectors.
- MC4 inline fuses, if necessary.
In the image above, you can see a pair of 2-to-1 (or Y) MC4 branch connectors, since I’m only connecting two solar panels in parallel. However, if you have more solar panels, you’ll require branch connectors with a matching number of inputs.
Now, to wire my two solar panels in parallel, the initial step was connecting the fuses to the positive leads of the solar panels.
Read more about fusing solar panels.
After fusing the solar panels, I joined the positive wires using a Female-Female-Male MC4 branch connector and connected the negative wires using a Male-Male-Female MC4 branch connector.
The wire on the left represents the negative end of the solar array. Using the extension cables, it should be connected to the negative PV terminal of the solar charge controller. The wire on the right is the positive wire, which needs to be connected to the positive PV terminal of the charge controller.
Solar Panels Series vs Parallel: What Is The Difference?
Whether you connect solar panels in series or in parallel, the total power output (in Watts) is the sum of the power generated by each solar panel. The difference between these two types of configurations is the total Voltage (Volts) and the total Current (Amps) of the solar array.
When you wire solar panels in series, you raise the Voltage of the system, while the Current stays the same.
Total Voltage (Volts) = Voltage 1 + Voltage 2 + Voltage 3 + Voltage 4
Total Voc (Open-Circuit Voltage) = Voc 1 + Voc 2 + Voc 3 + Voc 4
Total Vmp (Maximum Power Voltage) = Vmp 1 + Vmp 2 + Vmp 3 + Vmp 4
Total Current (Amps) = Current 1 = Current 2 = Current 3 = Current 4
Total Isc (Short-Circuit Current) = Isc 1 = Isc 2 = Isc 3 = Isc 4
Total Imp (Maximum Power Current) = Imp 1 = Imp 2 = Imp 3 = Imp 4
When you wire solar panels in parallel, you raise the Current of the system, while the Voltage stays the same.
Total Voltage (Volts) = Voltage 1 = Voltage 2 = Voltage 3 = Voltage 4
Total Voc (Open-Circuit Voltage) = Voc 1 = Voc 2 = Voc 3 = Voc 4
Total Vmp (Maximum Power Voltage) = Vmp 1 = Vmp 2 = Vmp 3 = Vmp 4
Total Current (Amps) = Current 1 + Current 2 + Current 3 + Current 4
Total Isc (Short-Circuit Current) = Isc 1 + Isc 2 + Isc 3 + Isc 4
Total Imp (Maximum Power Current) = Imp 1 + Imp 2 + Imp 3 + Imp 4
As an illustration, I’ll connect two identical 100W solar panels both in series and in parallel, and demonstrate the resulting voltage and current.
Here are the electrical specifications for each of these solar panels:
Let’s start with a series connection.
Solar panels in series:
As previously explained, in a series connection, Voltage increases while Current remains the same. Therefore, with these series-connected solar panels, we now have a solar string with the following specifications:
- Rated Power = 100 Watts + 100 Watts = 200 Watts
- Max. Power Current = 5.62 Amps
- Max. Power Voltage = 17.8 Volts + 17.8 Volts = 35.6 Volts
- Short Circuit Current = 6.23 Amps
- Open-Circuit Voltage = 22.5 Volts + 22.5 Volts = 45 Volts
However, the actual Voltage and Current that the string produces at a given moment will depend on the amount of sunlight available for the solar panels to convert into electricity and the type of solar charge controller you’re using.
In my case, I’m using an EPEVER MPPT charge controller. But as you can see in the image above, it was cloudy, and the solar panels were not receiving direct sunlight.
As a result, the string was only generating approximately 25 Watts of power instead of the full 200 Watts:
Power (Watts) = Voltage (Volts) x Current (Amps)
Power (Watts) = 42 Volts x 0.6 Amps
Power (Watts) = 25.2 Watts
Now, let’s explore how voltage and current differ in a parallel connection.
Solar panels in parallel:
As previously mentioned, in a parallel connection, the Current increases while the Voltage stays the same. With this setup, we now have a solar array with the following specifications:
- Rated Power = 100 Watts + 100 Watts = 200 Watts
- Max. Power Current = 5.62 Amps + 5.62 Amps = 11.24 Amps
- Max. Power Voltage = 17.8 Volts
- Short Circuit Current = 6.23 Amps + 6.23 Amps = 12.64 Amps
- Open-Circuit Voltage = 22.5 Volts
In this second test, the solar panels received more sunlight, although it still wasn’t optimal:
At 21 Volts, our parallel-connected solar panels were producing only 1.6 Amps, which amounts to 33.6 Watts:
Power (Watts) = Voltage (Volts) x Current (Amps)
Power (Watts) = 21 Volts x 1.6 Amps
Power (Watts) = 33.6 Watts
While the parallel connection in my test seems to yield more power, this is because the solar panels received a bit more sunlight. It’s important to note that a parallel configuration doesn’t always result in more power.
Each configuration has its own set of pros and cons, and your choice between them will depend on the specific requirements and limitations of your solar system.
Let me explain.
Solar Panels Series vs Parallel: Pros and Cons
Connecting solar panels in series:
- Simplicity and Cost: It’s easier and more cost-effective to connect solar panels in series. No additional parts are needed, which simplifies the arrangement and lowers expenses.
- Reduced Current: Series connections mean less current flowing through the wires, allowing for the use of thinner and more affordable wires, and eliminating the need for fuses.
- Charge Controller Requirement: When you wire solar panels in series, you’ll often need to use an MPPT solar charge controller. Using a PWM charge controller can make the solar panels susceptible to shading and mixed lighting conditions.
- Cost: MPPT charge controllers are a better technology and are typically recommended for higher system efficiency, but they are more expensive. This may not always be cost-effective, especially for small solar systems.
So, when to opt for a series configuration?
1- If you’re using an MPPT solar charge controller:
MPPT (Maximum Power Point Tracking) charge controllers have a valuable capability: they can decrease the voltage from the solar array while simultaneously increasing current at their output by the same ratio. This allows you to maintain a series configuration with a higher voltage without sacrificing power.
MPPT charge controllers also enable you to wire your solar panels in series because they can activate the bypass diodes within the solar panels if one of the panels receives less sunlight than the others, such as in cases of partial shading or mixed lighting conditions.
Learn more about solar panel shading.
Just be cautious to ensure that the maximum voltage from your solar array doesn’t exceed the input voltage tolerance of your MPPT charge controller.
Related: Make use of our MPPT calculator.
2- If you have mixed solar panels with similar amperage ratings:
When you have solar panels from different manufacturers with varying voltage and amperage ratings, it’s important to consider the implications:
As previously explained, in a series connection, the voltages from the panels add up while the current remains the same. With mixed solar panels, if the voltage and amperage ratings are not identical, the voltages still add up, but the current will be equal to the lowest current rating in the string.
However, if you have mixed solar panels with different voltage ratings but relatively close current ratings, it can still make sense to wire them in series. This can help you make the most of the available power output while managing variations in voltage ratings.
3- If you have long wire runs:
When determining the wire size between the solar panels and the charge controller, two key factors come into play:
- Current Load: The amount of current flowing through the wire. Higher current requires thicker wires to handle the load.
- Voltage Drop: The distance between the solar panels and the solar charge controller impacts the wire thickness required to mitigate voltage losses.
Wiring your solar panels in series allows for the use of smaller gauge wires. This is because the current is relatively low, and the higher system voltage can tolerate a higher voltage drop compared to a lower system voltage.
Connecting solar panels in parallel:
- Cost-Efficiency: Wiring solar panels in parallel allows you to use PWM charge controllers, which are more budget-friendly compared to MPPT charge controllers.
- Individual Panel Performance: In a parallel connection, each panel operates independently in terms of current production. If one panel is shaded or receives less sunlight, it doesn’t affect the current production of the other panels.
- Higher System Current, Lower Voltage: Parallel wiring leads to higher system current and lower system voltage, necessitating thicker wires to handle the current and limit voltage drop.
- Additional Components: A parallel configuration requires the use of extra components like branch connectors and fuses, which are almost always necessary when wiring solar panels in parallel.
So, when to opt for a parallel configuration?
1- If you’re using a PWM charge controller:
When using a PWM charge controller, you’ll need to make sure that the nominal voltage of the solar array matches that of the battery. For example, if you have two 12V solar panels charging a 12V battery with a PWM, these solar panels would have to be wired in parallel to minimize energy losses.
2- If you have partial shading and variable lighting conditions:
When solar panels are exposed to varying amounts of sunlight due to partial shading or facing different directions, parallel wiring reduces system losses.
Each solar panel operates independently, meaning one panel’s reduced output doesn’t impact the output of the others.
2- If you have mixed solar panels with similar voltage ratings:
When dealing with mixed solar panels that share the same nominal voltage (e.g., 12V) but have different current ratings, you can still wire them in parallel.
The total current of the array will be the sum of the currents from each panel, and the voltage of the array will match the lowest voltage rating in the array.