Solar energy continues to break records year after year. You only have to look back to see how solar panel installations have evolved in terms of energy production and installed capacity. Thanks to these well deserved achievements, more people are asking themselves every year whether they should install a solar energy system in their own homes. Of all the questions surrounding residential solar energy, one of the most common is how to connect solar panels. This is because the type of connection used between solar panels is important and is not simply a matter of logistics or appearance, as the way we connect a photovoltaic system affects its performance.
Solar panels in series or parallel
Photovoltaic panels can be connected in different ways depending on their intended purpose. Connecting solar panels in series, in parallel or using both configurations simultaneously produces different results, and each installation has a specific objective.
With a series connection, the voltages are added together while the current remains the same. With a parallel connection, the opposite happens: the currents are added together while the voltage remains constant. If we combine both types of solar connection, we increase both the voltage and the current. To discover the best option for your home, it is always advisable to seek the help of a professional who can prepare a solar panel connection diagram and subsequently carry out the installation.
How to connect solar panels in series
Connecting solar panels in series is currently carried out using 144 cell solar panels with power ratings of around 500 W, which are suitable for 24 V and 48 V solar installations.
The parallel connection is made by connecting the negative terminal of one solar panel to the positive terminal of the next.
With this configuration, the voltage remains unchanged, while the currents generated by the photovoltaic panels, measured in amperes, are added together. This also makes it necessary to use maximum power point tracking controllers, or MPPT (Maximum Power Point Tracking), which regulate the high voltage to generate usable energy. By using MPPT controllers, we can take advantage of the higher voltage to extract up to 25% more power. This is why connecting solar panels in series is recommended for homes and installations with medium to high electricity consumption.
How to connect solar panels in parallel
Parallel connections for solar panels are generally used with 12 V solar panels containing 36 photovoltaic cells, such as EcoSolar models, and also with 24 V panels containing 72 cells. Panels with 36 and 72 cells are known as off grid panels and must always be connected to a conventional solar charge controller (PWM).
Unlike a series connection, in a parallel connection the positive and negative terminals of the solar panels are not connected to each other. Instead, the positive terminals are connected together, and the negative terminals are connected together in the same way, creating a positive and a negative circuit. This allows the voltage (V) of the panels to remain constant while their currents (A) are added together.
To carry out this type of installation, it is essential to connect the panels using double MC4 connectors to ensure that the parallel connection between two panels is watertight and protected against weather conditions. In addition to being connected using MC4 connectors, parallel solar connections must also be linked to a PWM controller.
Combined series and parallel connection
The purpose of this type of connection is to increase both the voltage and the current of the installation simultaneously.
A combined photovoltaic installation can be carried out when we have five or more solar panels with at least 144 cells and a power rating above 460 W (V x A). This is because we will not obtain an excessively high voltage, but we will be able to multiply the total current of the installation. As both current and voltage increase, we will need an MPPT controller, which will extract the maximum available current and voltage from the installation so that the energy can be used through inverter chargers.
| Connection | Voltage | Current | What to check |
| Series | Sum of panel voltages | Remains constant | Total voltage < Controller voltage |
| Parallel | Remains constant | Sum of panel currents | Total current < Controller voltage |
| Series and parallel | Sum of all voltages | Sum of all currents | Both limits |
Can solar panels with different wattages be connected together?
Solar panels with different wattages can be connected together, provided that a series of specific guidelines are followed. If these guidelines are not followed precisely, the consequences can range from reduced performance to serious faults in the solar system.
- Configuration of photovoltaic connections: As we have seen throughout this article, the way solar panels are connected produces different results in terms of the voltage and current generated by the photovoltaic system. Care must therefore be taken to ensure that the connected systems are properly balanced, avoiding mismatches and optimising energy production.
- Voltage and current compatibility: To use any of the connection configurations described above, the most important thing is to ensure that the output voltages are compatible. The panels must have similar operating voltages, otherwise they could cause problems in the system, imbalances and reductions in performance.
- Charge controllers and inverters: MPPT controllers and inverters or microinverters are very useful tools for managing and optimising differences in the electrical loads and currents of our solar panels. Thanks to these devices, we can maximise productivity and maintain balance throughout the system.
In general, installing solar panels with different wattages does not make much sense, especially in residential settings. In these cases, the usual approach when planning a photovoltaic installation is to consult a professional. A photovoltaic technician will prepare the solar panel connection diagram that best suits your home and your requirements. This photovoltaic connection diagram will be optimised in terms of both performance and cost to deliver the best possible results from the installation.
Now that you know how to connect solar panels, are you ready to give it a go, or would you prefer a specialist company such as Prot Energía to carry out the project?
