The Secrets to Connecting Different Solar panels in Series or Parallel- The Definitive Guide

In this article we show you:

The best practices for mixing different solar panels

How to squeeze more solar power by using different solar panels and “breaking” the best practices at the same time

Let’s get straight to the point.

The basics of connecting different photovoltaic panels in series or parallel

Mixing solar panels of various voltage or wattage, or produced by different manufacturers, is a frequently asked question by most DIYers.

Though mixing different solar panels is not recommended, it’s not forbidden and things would be ok as long as each panel’s electrical parameters (voltage, wattage, amps) are carefully considered.

When you intend to wire two panels produced by different vendors, the vendors are not the problem.

The problem is in different electrical characteristics of the panels, together with different performance degradation.

We put solar panels together to increase the solar-generated power.

Connecting more than one solar panel in series, in parallel or in a mixed-mode is an effective and easy way not only to build a cost-effective solar panel system but also helps us add more solar panels in the future to meet our increasing daily needs for electricity.

How to connect your solar panels depends on:

The type of your solar panels system,

The solar power you want to generate,

The other system components, such as a charge controller, battery, and inverter.

There are two main types of connecting solar panels – in series or in parallel. You connect solar panels in series when you want to get a higher voltage.

If you, however, need to get higher current, you should connect your panels in parallel.

Should you need both a higher voltage and a higher current, you have to apply both connection modes, which means that a part of your solar panels should be wired in series, while the remaining ones are to be wired in parallel.

The most important to remember is that both connection modes provide you with a higher wattage.

Therefore, if the power output of a solar panel cannot alone meet your daily electricity needs, you should think of adding more such panels to it, whether in series or in parallel.

To get the maximum efficient solar panel system, however, you should keep some basic principles related to connecting solar panels.

Last but not least don’t forget about the overcurrent protection of the solar panels and the solar power system!

Wiring solar photovoltaic panels in series

As we said above, when connecting solar panels in series, we get an increased wattage in combination with a higher voltage.

Such ‘higher voltage’ means that series connection is more often applied in grid-tied solar systems where:

1) the system voltage is often at least 24 volts, and

2) the solar array output voltage is fed to an inverter or charge controller of a typically higher input voltage compared to off-grid systems.

Connecting in series means joining the positive terminal of a solar panel to the negative terminal of the next solar panel until eventually you are left with one free positive and one free negative terminal of the array, which are to be connected to the input either of the inverter (in case of a grid-tied system without a battery backup) or the charge controller (in case of a grid-tied system with a battery backup or off-grid solar panel system).

When you connect solar panels in series, the total output current of the solar array is the same as the current passing through a single panel, while the total output voltage is a sum of the voltage drops on each solar panel.

The latter is only valid provided that the panels connected are of the same type and power rating.

Let’s consider the depicted below solar panels designated for a 12V solar panel system, operating at their Maximum Power Point, while delivering the depicted voltage and current that correspond to this power tracking point.

Wiring solar panels of different ratings in series

Here is a series connection of solar panels of different voltage ratings and the same current rating:

You can see that if one of the solar panels has a lower voltage rating (and the same current rating) compared to the remaining panels, the output power is lower than in the previous example but the loss is not significant. Things, however, are entirely different if you connect in series panels of different current ratings.

You should, however, have in mind that the current produced from а solar panel depends on the ambient temperature, solar cells temperature, and solar irradiance.

If the lower wattage solar panel is from different series or a different brand, it might behave differently under the same ambient conditions.

For example, if under the same environmental conditions the solar panel of the different wattage (i.e., 136W) has a lower current (for example, 7.5A), it would drag the performance of the whole solar array down, because it would limit the solar array’s current to 7.5A.

The performance of the solar array is as strong as the performance of the weakest element.

In a series connection, such a weak element is the solar panel with the lowest current.

The following example reveals this in more details.

This time we have a series connection of solar panels of different voltage ratings and different current ratings:

In this picture, you can see that a total of three different types of solar panels are used.

Each panel type has its own voltage, current, and power rating.

The total current here is determined by the panel of the lowest current rating and, as a result, the total wattage is severely reduced (by 40%) compared to the previous example where the loss of output power is not so significant.

Furthermore, if you take a look in the first panel in the row, and assume that you have wired four such panels in parallel, then the total output power would be: 4 x 85W = 340W.

Just compare this to the dramatically reduced wattage of 365W, and you’ll find out that if you connect in series solar panels with different voltage and current ratings, the total output power is determined mostly by the solar panel of the lowest rating!

What is more, let’s imagine an ideal fictitious situation where the current does not influence the performance of the solar array – the total harvested solar power would be 515W (85W+126W+152W+152W)!

Wiring solar pv panels in parallel

The next basic type of connecting solar panels is in parallel.

Connecting solar panels in parallel is just the opposite of series connection and is used to increase the total output current of the array, and hence the total output power while keeping the same voltage.

‘The same voltage’ is the system voltage which for off-grid solar panels systems is usually as low as either 6V or 12V.

For this reason, parallel connection is more typical for off-grid systems.

In the parallel connection, all the positive terminals of the panels are joined together, and all the negative terminals are also joined together.

Eventually, you have one common positive and one common negative terminal of the solar array which are to be connected to input either of the inverter (in case of a grid-tied system without a battery backup) or the charge controller (in case of a grid-tied system with a battery backup or off-grid system).

When you connect solar panels in parallel, the total output voltage of the solar array is the same as the voltage of a single panel, while the total output current is a sum of the currents passing through each panel.

The latter is only valid provided that the panels connected are of the same type and power rating.

Wiring solar panels of different ratings in parallel

Here is a parallel connection of solar panels of different voltage ratings and the same current rating:

As you can see, things are getting worse, since the total voltage of the array is determined by the solar panel of the lowest voltage rating: we received 11% loss of installed solar power.

Let’s see what happens when we bring even more diversity and connect in parallel solar panels of different voltage and current ratings:

Things are steadily getting worse, but it’s evident that what you lose here as wattage is much lower compared to connecting different solar panels in series.

Important to summarize:

Both in series and parallel connection, plugging a panel of a lower power rating to the array drags the whole output power down.

The lower the rating, the higher the loss of solar generated power.

This, however, is much more crucial for panels connected in parallel.

Therefore, if you want to get the maximum power from your solar array, you should only connect similar panels.

Mixing different panels, whether connected in series or in parallel, ALWAYS reduces the installed wattage.

Furthermore, if you don’t have any other option than wiring dissimilar panels, you should know that:

1) For series connection – the same current rating of the panels is more important.

2) For parallel connection – the same voltage rating of the panels is more important.