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Should you wire solar panels in parallel or series?

Should you wire solar panels in parallel or series? In this blog post, we’ll explain the difference between parallel and series wiring and give you some examples of each so that you can make your informed decision.

What is wiring solar panels in parallel?

When solar panels are wired in parallel, the positive terminal from one panel is connected to the positive terminal of another one, and the negatives also get connected in the same manner.

In this configuration, the voltage of the system doesn’t change however the current increases.

Parallel connections with multiple panels can be used to keep the voltage consistent and increase amps.

For example, if you had 4 pieces of 12 volts 5 amp solar panels wired together in series; then that would be equivalent to having a system with 12 volts and 20 amps.

This type of connection is often found in 12V systems, as it allows for more charging capabilities without changing voltages throughout the system.

What is wiring solar panels in series?

A series connection means a positive terminal of one panel is connected to the negative terminal of another panel.

Solar panels when connected “in series” will yield higher voltages than those without connection because each panel’s individual voltage is added onto another as electrical current flows from one end of a stringing wire where it enters through lead wires on either side into the next panel.

So, if you link two solar panels with rated voltages of 40 volts and 5 amps in series, the series voltage will be 80 volts while the amperage will remain at 5 amps.

Pros and use cases of wiring in parallel

Independent components

A parallel wiring configuration provides a more reliable method for connecting all of your panels together.

Using parallel wiring, if you have a problem with one of the panels you can disconnect that particular set from the circuit and you can continue to use your other panels as normal without disrupting the entire system.

This allows for more flexibility to troubleshoot issues with panels without having to disconnect the whole system.

Consistent voltage

Parallel wired solar panels mean will offer a more consistent voltage throughout the circuit. This means if one set of panels isn’t working as well, it doesn’t affect the system output.

Doesn’t require MPPT charge controller

Because parallel configuration does not add voltages, your charge controller is not required to handle high voltages.

This is especially important if you have a lot of solar panels that need to be wired together.

You will not need to invest in a more expensive MPPT (Maximum Power Point Tracking) charge controller. A PWM (pulse width modulation) controller should work fine in parallel wiring configurations.

Cons and limitations of wiring in parallel

Requires identical equipment

When you wire solar panels in parallel, it’s important to make sure that they are identical and have the same capacity. Otherwise, you will likely not get the most performance from your panels.

Works inefficient in long distances

The disadvantage of parallel wired systems is that high amperage is difficult to transport over long distances without the use of extremely thick wires.

Systems as powerful as 1000 watts may produce more than 50 amps, which is difficult to transfer, especially if your panels are more than 10 feet away from your controller. In this case, you would need to use 4 AWG or thicker wire and purchase a branch connector or combiner box for each panel used in the system.

Pros and use cases of wiring in series

Ideal for panels with less power output

If you have smaller power output panels you can place them in series to make up a certain voltage value. This way they can work together in order to offer sufficient voltage for your needs.

Less energy loss during the transfer

Panels connected in series are more efficient in terms of preserving the energy production in a solar panel system. This can be a particularly important considerations if you need to use longer wires in between panels.

Cons and limitations of wiring in series

Harder to maintain

In a series circuit, the electricity must pass through each component before moving on to the next. If one of these components fails or breaks down then that will cut off power from all other parts in this loop.

Requires an MPPT charge controller

In order to normalize total voltage you get from a series configuration need a charge control that can handle it.

Connecting more panels together chances are higher you will need an MPPT charge controller especially if your panels power output is high.

When you should choose one over the other?

To choose between series or parallel wiring your solar panels, you need to answer the following questions.

  • Is the power output of your panels the same?
  • How much voltage your panels can provide?
  • What kind of charge controller you have?
  • Are you going to get an MPPT charge controller that can accept higher voltages or a PWM charge controller?

In order to get the best use out of your parallel configuration, make sure that all panels in a given system are at least very similar.

If you have two panels, each of which is 100Watts and provides 20V, wiring them in parallel is perfectly fine. It’s even better if they’re made by the same company; however, this isn’t required for parallel configuration to work.

When panels of unequal wattage capacity are connected in parallel, the power output is not optimal.

If one panel provides 100Watts and another provides 80Watts, they can still work together but you are going to be losing some power there on that 100Watts panel.

In a series configuration, your panels will work together to produce a higher voltage output. As a result, you must ensure that your charge controller can handle that amount of voltage.

It is preferable to use an MPPT charge controller capable of accepting high voltage and converting it to more amps for your charging system.

Power Output

What are the effects of choosing series or parallel connections on your power output?

Assuming that you chose the right material, wire sizes, panels, and installation method and that you have perfect summer conditions, it doesn’t really matter whether you installed your panels in a series or parallel.

Both systems will produce the same amount of power and will be equally efficient in terms of energy use.

During low irradiance like heavy overcast, at sunrise, or at sunset things work a little differently.

When only a small amount of sunlight touches the panel, it generates a small amount of voltage. In order to function, the solar charge controller requires a certain amount of voltage.

The voltage will not increase if your panels are connected in parallel. When your panels are connected in series, the voltage required to operate is higher than when they are connected in parallel under low irradiance conditions.

Partially shading is an entirely different story. It occurs when a portion of a solar panel is shaded by an object such as a tree, bird, or mouse, among others.

Let me tell you something first in order to better explain the subject. Solar panels are made up of identical solar cells. Solar cells are the black squares that are all connected in series in one long string across the panel.

If a single cell in a solar panel is shaded from any source, that cell will now produce less power.

Assume it produces half as much electricity as before. This means that even if all of the other cells have received enough sunlight to function at full capacity, the entire panel will be dragged down by this one cell.

However, there is a workaround for this, and almost all solar panels come with integrated bypass diodes. These allow to cut off that part of the panel to isolate this cell and let it function at full capacity.

When the drop in performance reaches a significant level of 5-10%, bypass diodes cut in the shaded cells. If it cuts in, only that portion of the panel will be lost; the rest of the panel and all other panels will continue to function at their full capacity.

If you have partial shading on just one panel, that one panel will reduce the total output while all other panels in the system perform at 100%.

You must first determine what type of partial shading pattern is likely to occur frequently, and then determine which wiring configuration is best for you.

Let me give you an example:

If you have a number of rectangular solar panels and connect them in a series. That would be installed on a mobile platform, such as an RV or boat.

Typically, you’ll want to align the shade figure of your vents, AC unit, and so on. You want to align that shade figure with the length of your solar panel.

This would make sense since the shadow would only hit a portion of the solar panel, and if bypass diodes are installed and only this portion of the panel will be left out.

Or if not, only this solar panel will reduce its output rather than all of the solar panels combined.

Keep panels as small as possible

Make sure that your panels are as small as possible, because if one panel is shaded then the rest will be able to do their job at 100%.

Have more bypass diodes in your system

If you have more bypass diodes in your system, it will be more resistant to partial shading. Because bypass diodes will kick in to cut out the shaded section, the rest of the panel will function normally.