Wiring Solar Panels – Parallel Vs. Series Stringing

The basic difference between solar panels in series and solar panels in parallel is their wiring. But beyond that, the expected output voltage and output current from both types of connections are markedly different.

Choosing the right mix of series and/or parallel wiring for your system isn’t always easy. With solar panels in series, we’ll expect an output voltage that is the sum of the individual panel voltages. But with parallel connections, the output voltage is not summative.

On the flip side, when wiring solar panels in parallel, the output current is the sum of the amperages of each panel in the array. But with series connections, the output current is not a total of each panel’s amperage.

Ordinarily, if we were trying to set up a solar-energy generating system with high voltage, we’ll probably opt for a series connection. But if we wanted one with high amperage, a parallel connection might be the preferred option. But then, it’s never really as simple as that since the type of charge controller in a solar system plays a huge role in determining panel circuitry.

Comparison Chart

Output VoltageSum of the voltages of each panel in the array.The voltage of just one panel in the array (if the panels are identical).
Output CurrentThe amperage of just one panel in the array (if the panels are identical).The sum of the amperages of each panel in the array.
Solar Charge ControllerMPPTPWN
Wire SizeThinner wires (large gauge wires)Thicker wires (small gauge wires)
Type of AppliancesCan support relatively larger appliances.May not support large appliances.
ShadingThe enrtire system is sensitive to shade.Not quite as sensitive to shade.
Type of SystemTypically used in large solar systems.More common in small solar systems.

Solar Panels in Series

Voltage and Amperage

The total voltage of solar panels in series is the sum of the voltage of each panel in the array. However, the total current of identical solar panels wired in series is equal to the amperage of just one of the panels.

When we do not use the same panels in a series connection, the output current would be the amperage of the solar panel with the lowest amperage rating.

For context, if we have four solar panels connected in series, all rated 5 amps, the output current of the array would be 5 amps. But if we had four solar panels in series with three rated 5 amps and one rated 3 amps, the output current of the array would be 3 amps.


To connect multiple panels in series, we connect the negative terminal on one solar panel to the positive terminal on another panel. We repeat this connection until all the solar panels are connected. In the end, we’ll end up with two solar panels that have one free terminal each (one positive, one negative).

The free terminals will serve as the terminals that transfer the power output to the charge controller.


As mentioned already, we wire solar panels in series when we want a high system output voltage. A high output voltage is particularly useful when we are constructing large solar systems.

Also, if we want lower voltage drop in our solar energy system, we can achieve it by using series connections. The high voltage of solar panels in series comes with relatively less current. When we have less current, we can use thinner wires. With thinner wires, we can have less voltage drop.

Charge Controller

When we wire solar panels in series, we typically use them alongside an MPPT charge controller. One reason for this is that MPPT controllers can handle high voltage systems better than the alternative (PWM). While they can handle output voltages as high as 48v, PWMs typically do not go above 24v.

Apart from that, MPPT controllers can efficiently utilize the high voltage produced by your solar array. Since the voltage they get from the solar array is higher than the voltage of the solar batteries, they can work above the battery voltage. As a result, they can optimize charging even when the sun isn’t very hot.


The primary drawback of a series system is sensitivity to shade. Basically, if one of the panels in an array connected in series is affected by shade, the effect will spread to the remaining panels. The entire array may not generate power until the shaded panel starts getting some sunlight again.

Going by the above, series connections are best used in an unshaded spot.

Solar Panels in Parallel

Voltage and Amperage

The output voltage remains the same throughout parallel systems even after wiring multiple panels. However, the output current increases as you add more solar panels.

So, if we connect four 12v, 5 amps solar panels in parallel, the output voltage of the array would be the same at every point in the circuit. But the output current would be 4 x 5 = 20 amps.


Parallel connections are pretty much the opposite of solar panels in series. When wiring solar panels in parallel, the positive terminals of the solar panels are connected to each other. The negative terminal are also connected together.

In the end, we’ll have one positive terminal and one negative terminal. These free terminals transfer the solar output to the charge controller.

Typically, when wiring multiple solar panels, a solar photovoltaic array combiner (also known as solar panel combiner box) is used to connect the terminals. You could also use branch connectors.

So, when wiring solar panels in parallel, the positive terminals of the solar panels converge at the positive connector of the combiner box. Then the negative terminals join each other at the negative connector.


We use parallel connection in systems where we need high output current and low voltage. Generating low voltage gives us the opportunity to use PWM controllers, which are not as expensive as MPPTs.

If we were to use PWMs with a high-voltage system, the battery will bring the array’s output voltage down to match its voltage. But then, this will lead to significant voltage drop and a consequent power loss.

We also use parallel connection when our array is in a spot where one panel or two panels can be shaded. When solar panels are in parallel, even if one panel gets shaded, the system will keep generating power.

Charge Controller

When a solar array uses parallel connections, it is typically connected to a PWM solar charge controller. This is especially true if the system is a low-voltage system.

As mentioned earlier, PWM controllers are typically rated 24v or lower (12v). So, since parallel wiring will not generate a higher voltage, a PWM would be able to handle them.

Also, since we typically use parallel wiring in low-voltage systems (small systems), installing an MPPT controller will not be cost-effective. Using the lower cost PWM controller generally makes more economical sense.


The primary drawback of a parallel configuration is that one must use a thick wire (small gauge wire).

Thinner wires offer more resistance against the large current coming from a parallel system. This may cause the wires to heat up pretty fast while preventing the current from going far.

However, with a smaller gauge wire, there’s more surface area. So, there are more electrons to move through the circuit.

Another drawback of a parallel array is that large appliances may not be able to run on it. Large appliances typically need higher voltages to run. But with parallel systems, we rarely have high voltages. Hence, the possible incompatibility.

Also, when we wire panels in parallel, we typically need a branch connector or combiner box. But we may not need that for a panel array in series.

Cost Comparison

Cost of Charge Controller

Solar panels wired in series use MPPT charge controllers, which are more expensive than the PWM used in parallel arrays. So, you will spend more on a charge controller for a series system.

Cost of Wiring Solar Panels

Since series array generate less current than parallel array, they can use higher gauge wires (thinner wires). Conversely, parallel arrays need smaller gauge wires because of their high output current.

So, when setting up a parallel array, you may spend more wiring. Of course, factors like wire length may come to play here.

Cost of Battery Bank

Since they use PWMs, the battery bank of a parallel system typically runs at the same voltage rating as the array. So, since parallel arrays do not generate very high voltages, they will not need high-voltage batteries in their battery bank. As a result, they usually use low-voltage batteries, which are relatively less expensive.

Conversely, since they use MPPTs, we can use high-voltage batteries in the battery bank of a series system, if we want. Of course, when opting for higher voltage batteries, we’ll spend more.

Combining Panels With Different Electrical Ratings

Generally, when connecting solar panels in series or parallel, it is better to use identical panels. However, if you choose to combine panels with different ratings in series, you can expect that the system’s current would be that of the panel with the lowest amperage.

Similarly, if you combine panels with different electrical ratings in parallel, the system’s voltage would be closer to that of the panel with the lowest voltage rating.