Solar panel series vs parallel: What is the difference?
When you wire solar panels in series or in parallel, you control the voltage (Volts) and current (Amps) of your solar array.
By connecting solar panels in series, you increase the voltage of the system without increasing the current. When you connect solar panels in parallel, you increase the current without increasing the voltage.
In other words, while series-connected solar panels mean higher PV system voltage, parallel-connected solar panels mean higher PV system current.
To understand this better, we’ll use the example of 4 identical solar panels wired in series, parallel, and series-parallel.
Series connection:
If you connect 4 identical solar panels in series, the total voltage of the string becomes the sum of the voltages of these solar panels, and the current from the string is equal to the current of a single solar panel.
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 (Optimum Operating Voltage) = Vmp 1 Vmp 2 Vmp 3 Vmp 4
since all of these voltages are identical, the total voltage is:
Total Voltage (Volts) = 4 x Single Solar Panel Voltage
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 (Optimum Operating Current) = Imp 1 = Imp 2 = Imp 3 = Imp 4
Parallel connection:
If you connect 4 identical solar panels in parallel, the total voltage is equal to the voltage of a single solar panel, while the total current is the sum of currents from all 4 panels.
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 (Optimum Operating 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 (Optimum Operating Current) = Imp 1 Imp 2 Imp 3 Imp 4
since all of these voltages are identical, the total current is:
Total Voltage (Volts) = 4 x Single Solar Panel Current
Series/Parallel connection:
This is a type of configuration that has both Parallel and Series connections. Every 2 solar panels are connected in series with each other, forming 2 strings, and the 2 strings are then connected in parallel.
In such a setup, the total voltage of the solar array will be equal to the voltage of a single string, and the total current of the solar array will be equal to the sum of the currents of both strings.
Since each string consists of 2 solar panels in series, the voltage of each string is equal to the sum of the voltages of the 2 solar panels:
Total Voltage (Volts) = Voltage of one string = Voltage 1 Voltage 2 = Voltage 3 Voltage 4
Total Voc (Open-Circuit Voltage) = Voc 1 Voc 2 = Voc 3 Voc 4
Total Vmp (Optimum Operating Voltage) = Vmp 1 Vmp 2 = Vmp 3 Vmp 4
The current of each string will be equal to the current of one solar panel, therefore, the total current of the solar array is equal to the sum of the currents of 2 solar panels:
Total Current (Amps) = Current of string 1 Current of string 2 = Current 1 Current 3 = Current 2 Current 4
Connecting solar panels in series vs parallel: how is it done?
Solar panels have a special type of connector at their terminals, which is referred to as an MC4 connector:
Each solar panel will have a female and a male MC4 connector. Generally, the female MC4 connector represents the negative terminal of the solar panel, and the male MC4 connector represents the positive terminal of the solar panel. However, this isn’t always the case.
In any case, before you make any connections, you’ll need to identify which MC4 connector is the positive and which is the negative.
There are also MC4 branch connectors, which you’ll need if you’re going to have parallel connections in your setup:
The ones in the image above are 2 to 1, but if you have more than 2 solar panels (or more than 2 strings) that’ll be connected in parallel, there are also 3 to 1 or 4 to 1 MC4 branch connectors.
Now let’s see how each type of connection is achieved.
How to wire solar panels in series?
To wire solar panels in series, connect the positive MC4 connector (male connector for example) of the first solar panel, to the negative MC4 connector of the next solar panel, and so on. When you’re done, you should have 2 unconnected terminals at each end of your string, a positive and a negative.
Here’s an example of 4 solar panels wired in series:
The unconnected positive and negative terminals of the string can then be connected to extension cables which will connect the string to the solar charge controller.
These extension cables will each have an MC4 connector on one end to connect to the solar panels, and stripped on the other end to connect to the solar charge controller.
How to wire solar panels in parallel
To wire solar panels in parallel, you’ll need to connect all the positive terminals of the solar panels together to form the positive terminal of the solar array, and all the negative terminals of the solar panels together to form the negative terminal of the solar array. This can be done using MC4 branch connectors.
Here’s an example of 4 solar panels connected in parallel using 4-1 MC4 branch connectors:
The output of each branch connector can then be connected to the extension cables that lead to the solar charge controller.
How to wire solar panels in series and parallel (series-parallel)
To wire solar panels in series and parallel, wire each string of solar panels in series (positive to negative). Then, using MC4 branch connectors, wire all the positive terminals of the solar strings together, and the negative terminals of the strings together.
For example, how to wire 4 solar panels in series-parallel?
To wire 4 solar panels in a series-parallel configuration, wire every 2 solar panels in series by connecting the positive of one solar panel to the negative of the other solar panel, forming 2 strings. You’ll then need to wire these 2 strings in parallel by connecting their positive terminals together and their negative terminals together.
Here’s an image that illustrates this:
How Connecting Solar Panels in Series Vs Parallel Differs?
Solar panels are made from silicon-made monocrystalline or polycrystalline solar cells. Solar panels differ in size, voltage, and output. Thus, the main difference faced in series or parallel arrangement is voltage and output.
Series Solar Panel Wiring
a) Voltage and Amps
For wiring solar panels in series, the positive terminal on one panel is connected to the negative terminal on the second one. The same pattern continues throughout the whole series. The overall voltage of the panel will be the sum of the voltages of all interconnected panels. The total current will be the output current of one panel.
For example, 3 panels with 18 volts and 6 amps are wired in series. The output voltage will be 54, which is the sum of 3 panels (181818), but the output current will be 6 for the entire series.
b) Best Applicable
Solar panels wired in series are best for unshaded. Since panels are connected in a series, their overall voltage is dependent on each other. If a panel or a part of a panel is shaded, it will bring down the power output of the entire system.
Series connection is best if you need a low ampere system and to calculate this multiply current by voltage. Higher voltage means lower ampere and this series will work well with less expensive wires. Also, it is easier to use.
c) Requirement
For a series of solar panels, you need a Maximum Power Point Tracking (MPPT) charge controller to regulate the voltage and current traveling from solar panels to the battery bank. With a Maximum Power Point Tracking charge controller, there will not be any power loss while maintaining the voltage.
Parallel Solar Panel Wiring
a) Voltage and Amps
All positive terminals on each panel are interconnected and the same is done for negative terminals. It means positive is connected with positive and negative with negative. The sum of amperes of all panels is the resulting current in such wiring. The total voltage of a single panel is the total voltage for the entire series.
For example, 3 solar panels of 18 volts and 6 amps each wired parallel will have 18 amps total output current (666) with 18 volts as its output voltage. There is a major difference between connecting solar panels in series vs parallel.
b) Best Applicable
Parallel-wired solar panels work independently; thus, they are best for mixed light condition requirements. Partly shaded solar panels or panels will not affect the overall output of the series.
Also, this wiring is ideal when a low-voltage system with Pulse Width Modulation (PWM) charge controller is preferred.
c) Requirement
Output charging current is increased if the nominal battery charging voltage matches with panel output voltage.
What are Solar Panel Series Vs Parallel Pros and Cons?
To understand the solar panel series vs parallel pros and cons, let’s first start by understanding the pros of series and parallel.
Pros of Series
- Lesser cables are required.
- Does not necessarily require thick cables.
- With the temperature of solar panels exceeding 25° Celsius, there is a drop in voltage. This drop increases with an increase in temperature but with multiple solar panels in series, a drop in voltage can be managed.
Pros of Parallel
- Does not deal with high voltages hence it is safe to handle.
- Either a Maximum Power Point Tracking (MPPT) or Pulse Width Modulation (PWM) solar controller can be used. A good pulse width modulation solar controller at an affordable price will also be sufficient.
- Mixed solar panels can be used
- The system does not need special cooling as the pulse width modulation solar controller does not produce excessive heat.
Now let’s learn about the cons of the solar panel series vs parallel.
Cons of Series
- The bypass diode and blocking diode are required for each panel to maintain a balance between panels.
- Due to heat generated by the MPPT controller, the voltage needs to be altered to suit the voltage of the RV.
- Needs expensive MPPT installation because a cheaper MPPT and a pulse width modulation (PWM) solar controller would not work.
- Series solar panels carry higher voltages; thus, it is dangerous.
- Without the same Voltage Maximum Power (VMP) and Open-circuit Voltage (Voc) ratings solar power harvesting will be the lowest Voltage Maximum Power (VMP) and Open-circuit Voltage (Voc) for all available panels in the series.
Cons of Parallel
- Multiple solar panels may not supply combined voltage to charge the battery because the connection combines amps.
- Thick cables in large quantities are needed. In connecting solar panels in series vs parallel you need to consider the pros and cons of both.
Formula for Calculating Solar panels connected in parallel:
Total Voltage = V1 = V2 = V3 = … = Vn, where V1, V2, V3, … Vn are the voltages of each solar panel.
Total Current = I1 I2 I3 … In, where I1, I2, I3, … In are the currents of each solar panel.
Please note that when solar panels are connected in series, the total voltage of the array will increase, but the total current will remain the same as that of the lowest current solar panel. When solar panels are connected in parallel, the total current of the array will increase, but the total voltage will remain the same as that of a single solar panel.
Connecting Solar Panels in Series (Practical Example)
For example, let’s say you have three 100W solar panels with the following specifications:
Voltage (V): 18V Current (I): 5.56A
In order to connect these solar panels in series, you will have to connect the positive terminal of the first solar panel to the negative (-) terminal of the second solar panel, and then connect the positive terminal of the second solar panel to the negative (-) terminal of the third solar panel, as shown in the diagram below:
The total voltage of the array would be:
Vtotal = V1 V2 V3 = 18V 18V 18V = 54V
The total current of the array would be:
Connecting Solar Panels in Parallel (Practical Example)
In order to connect solar panels in parallel, you will have to connect the positive terminals of all the solar panels together and the negative (-) terminals together. The total voltage of the solar panel array will be the same as that of a single solar panel, while the current will be the sum of the currents of each solar panel.
For example, let’s say you have three 100W solar panels with the following specifications:
Voltage (V): 18V Current (I): 5.56A
In order to connect these solar panels in parallel, you will have to connect the positive terminals of all three solar panels together and the negative (-) terminals of all three solar panels together, as shown in the diagram below:
The total voltage of the array would be:
The total current of the array would be:
Itotal = I1 I2 I3 = 5.56A 5.56A 5.56A = 16.68A
How to Wire Solar Panels in Series Parallel
Here’s a quick overview of how to wire solar panels in series and parallel. For more in-depth instructions, check out our full tutorial.
Series
To wire solar panels in series, connect the positive cable of one to the negative cable of the other.
Here’s a video showing you what I mean:
If you want to connect more in series, just connect the positive cable of each additional solar panel to the negative cable of your series string. You can string together as many panels as you want like this.
Parallel
To wire solar panels in parallel, you need to buy the appropriate branch connectors for the number of panels you’re wiring in parallel. (You may also need to buy inline MC4 fuses and connect them to the positive cable of each solar panel.) I’ll show you how to wire 2 panels in parallel using Y branch connectors.
To do so, connect the 2 positive solar panel cables to the compatible Y connector. Then connect the 2 negative solar panel cables to the other Y connector.
Here’s a video showing how to do this:
If you’re wiring more than two solar panels in parallel, pick the right branch connector for the number of panels you’ll be wiring in parallel.
H/T to Mowgli Adventures whose calculator was a big inspiration for this one. Their blog is amazing and you should definitely check it out!
How does a series solar panel connection work?
Let’s take a look at how we can connect some solar panels in a series circuit.
We’ll use an example of a series circuit connecting four 100 Watt solar panels. Each solar panel is 20 Volts and 5 Amps.
The circuit is formed by connecting the positive electrical terminal of one solar panel to the negative terminal of the next in a line and running a cable from each end of this line to the other components of our solar system. We can calculate the voltage current and power of this circuit as follows.
Total voltage = 20 Volts x 4 = 80 Volts
Total current = 5 Amps
Total power = 80 Volts x 5 Amps = 400 Watts
How does a parallel solar panel connection work?
When we take these same four solar panels and connect them in a parallel circuit, we run the cables from each panel separately into our solar system. We don’t join any of the solar panels together. We’ll see why this is important in a little while. This is what the voltage, current, and power of our parallel solar panel connection look like.
Total voltage = 20 Volts
Total current = 5 Amps x 4 = 20 Amps
Total power = 20 Volts x 20 Amps = 400 Watts
Even though the voltage and amperage of our series and parallel solar connections are very different, you can see that the final power output is the same.
So we’ve proved that there is no difference in the power output from a series or a parallel solar system when the voltage and amperage of all solar panels are the same. But things get complicated when you wire together panels with different voltage and amperage capacities.
The effect of mixing solar panels in serial and parallel connections
Now let’s make the same circuits with three 100 Watt solar panels of 20 Volts and 5 Amps and another 75 Watt panel of 25 Volts and 3 Amps. This is the total power of 375 Watts.
The difference here is that when you wire different solar panels in series, you need to use the lowest amp rating of all the panels.
Serial Connection
Total voltage = 20 Volts x 3 25 Volts x 1 = 85 Volts
Total current = 3 Amps (taking the lowest rating)
Total power = 85 Volts x 3 Amps = 255 Watts
Because we had to use the lowest amperage panel for the series connection, we ended up with a total power output of 255 Watts, resulting in a loss of 375 – 255 = 120 Watts of power.
Now, when you wire the same panels in a parallel connection, you need to use the lowest voltage.
Parallel Connection
Total voltage = 20 Volts (taking the lowest rating)
Total current = 5 Amps x 3 3 Amps x 1 = 18 Amps
Total power = 20 Volts x 18 Amps = 360 Watts
When using the panel with the lowest voltage for the parallel connection, we ended up with a total power output of 360 Watts, resulting in a loss of 375 – 360 = 15 Watts.
If you’re not careful when wiring solar panels of different capacities, you can lose a lot of power. In these situations, it’s essential to look at the ratings and calculate the effects of serial or parallel wiring. But there are also some other advantages and disadvantages of these wiring systems that you need to take into account.
Advantages and disadvantages of series and parallel wiring systems
Wiring
If you are running an electrical circuit with high amperage, you need a thick cable to carry the load. Think back to the water example, where you’d need a strong pipe to handle a powerful flow of water.
Wiring your solar panels in parallel means that you need cabling and components rated for high Amperage. If you use serial wiring for your solar system, there will be a higher voltage and low amperage, reducing the demands on your cables and components. If you’re uncertain about which wire size to choose for your solar setup, you might find our article on how to choose solar wire size.
The main benefit of parallel wiring
When you wire all your solar panels in parallel, the performance of one panel is not dependent on the performance of the other panels. But in a serial connection, if one solar panel is working at a lower capacity, it reduces the whole solar array’s performance.
This is important in case a panel in a series connection malfunctions. Also, if a particular panel in the series may be receiving less sunlight because of shade, the whole system’s power output will be reduced.
Summary
Now you have a good idea about the differences between serial and parallel wiring systems. Each has its benefits and drawbacks, and you’ll need to think carefully about which one to use.
If you plan to connect solar panels of different capacities, then a parallel connection is probably best. Parallel connections will help you avoid an underperforming solar panel lowering the output of your whole system.
But remember, depending on your specific system requirements and the specifications of your panels, it may be more complicated and potentially more expensive to wire and connect your solar panel system in parallel.
Perhaps one solution is to carefully check the placement and performance of your solar panels so that if you choose to wire them in series, you can minimize the risks of performance loss.
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