Solar Panels In Series or Parallel?

As the decision gets closer on whether to install solar panels, you start to hit some nitty gritty questions about these renewable energy systems.

One such question is whether to get solar panels in series or parallel? This is all to do with the configuration and technical set up. 

It’s usually left to the installer and their recommendations but it does no harm whatsoever to have some knowledge about this yourself as a homeowner. After all, it can impact your system’s performance, efficiency and overall energy output. 

This guide will look at the major differences between series and parallel connections, their pros and cons and help you determine which configuration might be best for your home.

In a series connection, solar panels are linked one after another – a bit like a chain. The positive terminal of one panel connects to the negative terminal of the next, creating a single path for the electric current to flow.

The key characteristic of a series connection is that it increases the overall voltage of the system whilst maintaining the same current. In this type of connection, the amperage (measured in amps) also remains the same as that of a single panel. This allows for the use of lighter and potentially less expensive cables, which can be advantageous in some installations.

This increase in voltage can be beneficial in many situations, particularly when you need to match the input requirements of certain inverters.

On the other side, parallel solar panel connections involve linking all the positive terminals together and all the negative terminals together. This creates multiple paths for the electric current to flow.

In a parallel configuration, the voltage remains the same as that of a single panel, but the current (measured in amps) is higher. This configuration often requires heavier, more robust cables to handle the increased current flow.

Parallel connections are often used when you need to increase the current output of your system without changing the voltage.

Pros and cons of series connections

Advantages of series connections

  1. Higher voltage – Series connections allow for higher voltage outputs, which can be beneficial for matching inverter requirements and reducing power loss over long cable runs.
  2. Less wiring – Generally, series connections require less wiring, which can reduce installation complexity and cost.
  3. Better for low light conditions – In low light, series-connected panels are better adapted to produce enough voltage to charge batteries or run inverters.
  4. Cable efficiency – Series connections allow for the use of lighter, less expensive cables due to lower amps.

Disadvantages of series connections

  1. Vulnerability to shading – If one panel in a series string is shaded or not working properly for whatever reason, it can significantly reduce the output of the entire string.
  2. Limited flexibility – It’s more challenging to add panels to a series-connected system after the initial installation, which might be problematic if you’re eventually planning on increasing your solar panel system size. 
  3. Higher voltage – The higher voltages produced by series connections require more careful handling and may necessitate additional safety measures.

Pros and cons of parallel connections

Advantages of parallel connections

  1. Good resilience – Parallel connections maintain a more consistent current output, even if one panel is shaded or not performing optimally.
  2. Easier to expand – Adding new panels to a parallel system is generally simpler than adding to a series system.
  3. Lower voltage – The lower voltage output can be safer to work with and may be preferable in some residential settings.

Disadvantages of parallel connections:

  1. More complex wiring – Parallel connections often require more wiring and more expensive cables, which can increase installation complexity and cost.
  2. Larger cables – The higher amps in parallel systems often need heavier, more expensive cables.
  3. Limited distance – Lower voltages in parallel systems may limit the distance between the panels and the inverter or battery storage systems due to voltage drop over long cable runs.

The choice between series and parallel connections can have a noticeable impact on your solar system’s energy output and how it meets your home’s energy needs.

Series connections, with their higher voltage outputs, are often preferred for grid-tied systems. Many grid-tie inverters require a minimum input voltage to work efficiently – series connections can help meet these requirements. This configuration can be particularly useful in the UK where sunlight is inconsistent across the year, as it helps to make sure the system can produce usable power even in less-than-ideal conditions.

Parallel connections are often favoured in off-grid systems or for those with battery storage. The consistent current output of parallel connections works well with battery charging systems. Check out this post on solar battery storage explained for more information on these energy-saving systems. 

Additionally, if your energy needs are likely to grow over time, the ease of adding panels to a parallel system can be advantageous.

It’s important to match your solar panel configuration with your inverter specifications. Most modern inverters can handle a range of input voltages and currents, but you’ll need to make sure your configuration falls within these parameters for efficient performance. Of course, your installer will be the expert here. 

The choice between series and parallel connections can also impact your potential energy savings. 

In ideal conditions with no shading issues, a series configuration usually produces more energy and greater savings. 

However, if your panels may be frequently exposed to shading, a parallel configuration might result in higher overall energy production and savings by allowing the unobstructed panels to continue operating at full capacity.

Installation considerations of series vs parallel solar panels

The installation process for series and parallel configurations differs in a few key aspects:

  • Series installation
    • Requires less wiring overall
    • May need higher-rated cables and connectors due to higher voltages
    • Often simpler to install, especially on straightforward roof layouts
  • Parallel installation
    • Requires more wiring and often additional components like combiner boxes
    • May be more complex to install, especially with a large number of panels
    • Can offer more flexibility in panel placement
  • Inverter compatibility
    • Series connections often work well with high-voltage inverters
    • Parallel connections can be suitable for systems using lower-voltage inverters

Space requirements can also differ. Whilst the panels themselves take up the same amount of space, parallel systems may require a little more room for wiring and components.

In terms of maintenance, series configurations are likely to require more attention. This is because a single underperforming panel can affect the entire string. 

Which configuration is best for UK homes?

As you might imagine, the best configuration for your UK home depends on a number of factors in order to set up the most effective solar panel system.

Roof space and layout are primary considerations. If you have limited roof space or a non-conventional roof layout, a series configuration might be more suitable due to its simpler wiring requirements. 

Shading is another big factor, especially in the UK where partial shading is common due to chimney stacks, nearby trees or neighbouring buildings. If this is the case, a parallel configuration might prove more efficient, as these setups are more resilient to partial shading issues.

Your current and future energy needs should also influence your decision. If you anticipate your energy requirements growing over time, it’s more straightforward to expand a parallel system. This configuration will give you more flexibility for additional panels in the future.

Inverter specifications play an important role in determining the best configuration. Many UK installations use string inverters, which often work well with series configurations. However, the specific requirements of your chosen inverter should guide your decision.

Benefits of hybrid series-parallel systems

In the UK, a common approach is to use a series-parallel hybrid configuration. This involves connecting several panels in series to form ‘strings’, and then connecting these strings in parallel. The strings help to increase the voltage and the parallel connections help to increase the current at the same time.

This approach balances the benefits of both configurations and can be particularly effective in dealing with the uncertain weather conditions that we encounter on a regular basis. 

These hybrid systems could offer the best of both worlds. The main advantages are: 

  • Flexibility – Hybrid systems can be designed to match a wide range of inverter specifications.
  • Resilience – If one panel in a string is shaded or malfunctioning, only that string’s output is affected, not the entire system.
  • Scalability – It’s relatively easy to add new strings to expand the system’s capacity.
  • Efficiency – The higher voltage of series-connected strings reduces power loss over cable runs, whilst the parallel connection of strings maintains good performance even if one string is underperforming.

Solar in series or parallel?

Choosing between series, parallel or hybrid configurations for your solar panel system is a key decision. Although series connections offer simplicity and higher voltages, parallel connections provide resilience and expandability. For many UK homes, a hybrid approach combining both configurations could be the best bet.

However, it’s important to remember that every home is unique. Factors such as roof layout, shading issues and your specific energy needs all play a role in determining the best configuration for your solar panel system. The potential impact on energy savings can be substantial, with the right configuration potentially saving you hundreds of pounds over time.

It’s always recommended to consult with a professional solar installer who will be able to talk you through the options you have and their recommendations. The idea is that with the right setup, your solar panel system can provide efficient, reliable renewable energy for decades to come, helping you reduce your carbon footprint and save on energy bills.

About the author 

Ben Hardman

Ben is a professional writer and the creator of sustainable living website TinyEco.com.
It's here where he helps people to reduce their environmental impact through simple, everyday choices. Away from the laptop, Ben loves spending time in the natural environment with his young family and Murphy the cocker spaniel.

Experience:
First Class BSc Biology degree (environmental and climate change focus)
Six years of working and writing in the environmental sector, including two years working at an international sustainability consultancy
Written for Ethical Consumer magazine, My Mother Tree, Unsustainable Magazine, Happy Eco News, Emission Index, PeakDistrict.org
Commented in The Independent, The Guardian, GreenMatch. Also featured on Radio 1's environmental special 'Minute of Me'

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