Which type of storage system is more popular in the UK, and why?

When considering solar energy storage systems for homes or small businesses in the UK, there are primarily two types: AC-coupled and DC-coupled systems. These terms refer to how solar panels are connected to the battery storage system.

Introduction to AC and DC Coupling

• AC-Coupled Systems: These systems link to the solar PV system at the AC load panel. They are popular for retrofitting because they do not require changes to the existing inverter setup.
• DC-Coupled Systems: These connect directly to the solar array, requiring a single inverter for both the solar panels and battery.

Popularity in the UK

AC-coupled systems are often more popular for retrofitting existing solar installations in the UK. Here is why:

• Retrofitting Flexibility: AC-coupled systems can be easily added to existing solar setups without needing to replace or adjust the current inverter. This is a major advantage for homeowners who have installed solar panels but want to add storage later.
• Flexibility in Charging: AC-coupled systems can charge from both solar energy and the grid, making them convenient for charging off cheaper nighttime electricity rates for morning use.
• Cost-Effectiveness: The ability to retrofit without additional inverter costs makes AC-coupled systems more cost-effective for those with existing solar systems.

However, DC-coupled systems have their advantages as well:

• Efficiency: DC-coupled systems generally have fewer conversion steps, which can result in slightly higher efficiency compared to AC-coupled systems. However, AC systems are not as efficient due to additional conversion steps, leading to a loss of about 10-15%.
• Simplified Design: DC-coupled systems have fewer components since they share an inverter with the solar panels.

Practical Advice

When choosing between these two systems, consider your specific situation:

For Existing Solar Installations

• AC-Coupled is often preferable for retrofitting due to its flexibility and cost-effectiveness.

For New Installations

• DC-Coupled might be more suitable if you are setting up a new system from scratch, especially if you want a more streamlined setup with potentially higher efficiency.

Common Mistakes to Avoid

• Not evaluating current system compatibility before choosing a storage system type.
• Not planning for future expansion or upgrades, which might require additional inverters or changes in system design.

In summary, while AC-coupled systems are more popular for retrofitting existing setups due to their flexibility and cost advantages, DC-coupled systems offer efficiency benefits for those installing new solar and storage systems together.