Series vs Parallel Wiring of Solar Panels

Let me take a guess:

You are confused because you are pretty much overwhelmed about the different wiring methods of solar panels. The manufacturer may have mentioned a thing or two about series and parallel wiring and left you with so many questions.

If you are new to solar panel systems, you may wonder, does wiring them in a specific way even matter? Short answer: yes, it does. The wiring of solar panels has a significant impact on how they are going to perform.

In this article, I will review series vs. parallel wiring of solar panels in detail.

Let’s see what I have in store for you.

Comparison Between Parallel and Series Circuits

Before we talk about the wiring of solar panels, let’s do a quick revision. What exactly is meant by parallel and series circuits? Here is everything you need to know:

Parallel Circuits

Have a look at the switchboard in your room. You will see there are different switches for different uses. Turning on the light, would not automatically turn on your fan. This is because your switchboard has a parallel circuit. What exactly do we mean by that?

In a parallel connection, current flows along the multiple routes. Let’s suppose one of the switches in your switchboard stops working. Now, would it affect the other switches in the same switchboard? Most certainly, it will not.

Since parallel circuits have multiple paths, the current will flow along with the switches that are working, ignoring the broken one.

Across every path, the voltage remains the same, whereas the current adds up. You can calculate the total current by adding up the amps from each path.

Series Circuits

To understand a series circuit, we will have a look at a simple example. Your refrigerator and freezer have a series connection. If you turn off the switch, both of them will stop working. What do you think is going on?

Contrary to parallel circuits, series circuits have a single path for the current to flow. The current doesn’t have any paths to divide itself. Therefore, it doesn’t vary. The overall current stays the same, whereas the voltage across each resistor in a series circuit varies.

In a series connection, voltage is added up while current stays the same.

Can you easily differentiate between the two circuit connections now? That’s great. Now, we will see how we can relate our knowledge regarding parallel and series circuits in a solar panel array.

Series vs Parallel Wiring of Solar Panels

Similar to batteries, solar panels also come with a positive and negative terminal. With the help of these terminals, you can connect the solar panels in the desired fashion. So, let’s start with the series wiring of a solar panel system as it is less complicated than the parallel wiring.

What Happens in Series Wiring of Solar Panels?

The assembly procedure is quite simple because you don’t need to use any additional equipment. Let’s suppose you have four solar panels. To connect them in series, you have to join the positive terminal of your first solar panel to the negative side of your second terminal. Once you have attached all the solar panels side by side, you will see they have formed a string.

In the series wiring of solar panels, you will need a single wire to connect each solar panel in a string. If you are planning to install solar panels for your house, then the wire should come from the roof.

Series wiring of three solar panels
Series wiring of three solar panels

Tip: You can add up as many solar panels in series as your charge controller can handle. This is usually 100V DC.

The total voltage and current stays the same until it reaches the charge controller, which is a device to regulates voltage and current. From there, it will charge your battery.

Wire Thickness

As you have wired the solar panels in series, the voltage across each solar panel sums up to the total voltage. On the other hand, the amperage of electrical current for each solar panel will stay the same.

If the current doesn’t increase, there is no need to use bigger cables. You can still use the cables that the solar panel comes with. You might have to increase the size when you have to cover large distances to reduce voltage drop.

What Happens in Parallel Wiring of Solar Panels?

Do you know why parallel wiring is more technical?

Any guesses?

Don’t worry; Here is the answer:

In parallel wiring, you don’t have to play with a single wire. This is where it gets a little complicated.

Besides that, your installer will most likely install a combiner box before the charge controller. The main purpose of a combiner box is to transfer the combined output from multiple solar panels strings to an inverter.

Parallel wiring of three solar panels
Parallel wiring of three solar panels

We will get to that part later on. For now, let’s see how to connect the solar panels in parallel.

As you know, parallel circuits have multiple wirings. This setup allows the current to flow in different paths. We will apply the same phenomena here.

For that, we need two centralized wires from a house roof.

  • The first central wire will attach with the positive terminal wires of the solar panels
  • The second centralized wire will connect with the wires of negative terminals.

Wire thickness

Here, you have to be mindful of the amperage of the electric current. It adds up while the voltage stays constant across each solar panel.

You can use the same thickness of cable that is supplied with the solar panel up to the combiner box. The parallel connection is usually made in the combiner box. You should use the appropriate wire size to go from the combiner box to the charge controller.

Wiring in parallel will be more expensive than series because of the cost of wire.

Is Parallel Wiring the Right Fit for your Solar Panels?

If you look at the circuits closely, you will realize that parallel wiring turns out to be a better option. If your home appliances have a parallel connection, they will continue to work independently.

However, there is a small catch. You may think it won’t make a difference if one of the panels stops functioning. The other panels will be there to cover up for the malfunctioning one, right? Well, things are slightly different here.

With parallel wiring of the solar panels, you will have less voltage and more amperage. Remember, you need a greater value of the voltage to charge a battery. The solar panels in parallel connection have to function around 75% capacity to produce enough voltage for charging batteries. That sounds like a lot of work, for sure.

In short, if your battery bank is 24 volts but the solar panels are 17 volts, it’s not very efficient to charge your batteries.

Is Series Wiring the Right Fit for Your Solar Panels?

On the other hand, the series wiring will give a greater value of voltage.

Can you join the dots now? The manufacturer may have suggested the series wiring because of this particular reason.

Another question: Does this mean there are no downsides of using the series wiring for your solar panels?

Unfortunately, it’s not perfect with the series wiring either. To be honest, a single shaded panel is enough to affect the overall performance of your solar panel system. That’s not something you are looking for. If have written an article about the effects of shading on solar panels. Check it out here: solar panel shading.

Hybrid Wiring of Solar Panels

Yes, you read that right. Your solar panel supplier can choose to combine the series-parallel wiring. The hybrid wiring is a bit more complicated but totally worth it.

It depends on the ratio between voltage and amperage. This particular type of wiring keeps a good balance between them. And most of the time, this wiring setup renders good performance from the solar panel systems.

However, you simply can’t ignore what you need solar panels for; this is the primary deciding factor for your solar-panel wiring. Your installer will install the solar panel system according to your requirements. Having said that, what may work best for you probably won’t work best for someone else.

hybrid connection of solar panels
hybrid connection of solar panels

Conclusion

  • Use series wiring if you have no shade on your solar panels. Be mindful of winter conditions when the sun is lower. Go as high in voltage as the input of your solar charge controller permits.
  • You can use hybrid connections if your series connection has reached 100Volts DC.
  • If you expect shade, use parallel connections. This will be more expensive in wiring cost but you will get better performance of the panels.

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