Can I retrofit a storage system to my existing solar panels?

Yes, you can retrofit a storage system (solar battery) to your existing solar panels in the UK. This process involves adding a battery system to store the excess electricity your solar panels generate during the day, so you can use it later when the sun isn’t shining, reducing your reliance on the grid and cutting energy bills.

How retrofitting solar storage works

Retrofitting means adding battery storage to an already installed solar PV system. This is a common and increasingly popular upgrade for UK homeowners and small businesses who want to maximise their solar investment.

• An installer will assess your current solar setup.
• They will fit a battery storage system, usually alongside an inverter that manages the flow of electricity between your solar panels, battery, home, and the grid.
• Once installed, excess solar energy charges the battery.
• Your home or business can then draw on this stored energy when your panels aren’t producing enough power.
• Any unused energy after your needs are met can still be exported to the grid.

The installation usually takes just one day and does not require changes to your existing solar panels or to government schemes like the Feed-in Tariff if you have one in place.

DC-Coupled vs AC-Coupled Storage Systems

When retrofitting a battery storage system, you have two main types of technologies to consider, which differ mainly in how the battery integrates with your solar panels and your home’s electrical system.

DC-coupled storage system

• The battery connects directly to your solar panels' DC (direct current) output before it is converted to AC (alternating current) for your home.
• This configuration is often more efficient at storing solar energy because it reduces energy loss from multiple power conversions.
• However, upgrading to a DC-coupled system often requires replacing or significantly modifying your existing inverter to a hybrid inverter that can handle both solar panel input and battery charging.
• DC-coupled systems are more common in new solar installations but are becoming easier to retrofit with recent technologies.

AC-coupled storage system

• The battery is connected on the AC side, meaning after your solar panels’ electricity has been converted to AC by your existing inverter.
• This system uses a separate storage inverter to convert AC power back to DC to charge the battery and then back to AC when discharging.
• AC-coupled systems are simpler and faster to install on existing solar setups because they don’t interfere with the original inverter.
• They offer greater flexibility and are currently the most popular solution for retrofits in the UK.

Practical considerations for UK homeowners and small businesses

Advantages of retrofitting storage

• Energy independence: Store your solar energy for use at night or during outages.
• Cost savings: Use stored solar power during peak tariff times to reduce electricity bills.
• Support grid stability: Reduce peak demand on the National Grid.
• No panel changes needed: Your existing solar system stays intact.
• Fast installation: Usually completed in one day with minimal disruption.

Common pitfalls and mistakes

• Choosing incompatible equipment: Not all batteries or inverters work with every existing solar system.
• Ignoring electric regulations: Retrofitting may require electrical upgrades and notifying your grid operator.
• Overlooking battery size: Too small batteries may not deliver significant savings; too large can be a poor investment.
• Not considering system efficiency: DC-coupled systems can be more efficient but harder to retrofit; AC-coupled systems are easier but slightly less efficient.
• Neglecting warranty and certification: Ensure your retrofit battery and installation comply with UK standards and have warranties.

Recent UK developments and policies

• The increase in electricity prices and grid demands has accelerated interest in battery retrofits across 1.2 million UK homes with solar PV installed.
• The UK government encourages home energy storage as part of its energy security and net-zero goals.
• Some companies now offer retrofit solutions that simplify adding DC-coupled storage without replacing your inverter.
• Feed-in Tariffs are no longer available for new solar installations, making energy storage a more attractive investment.
• Certain tariffs and smart export guarantees let you earn money by exporting surplus energy, especially when combined with storage.

Summary advice

• Assess your current system with a qualified installer to determine compatible retrofit options.
• Decide between AC-coupled and DC-coupled batteries: For most retrofits, AC-coupled batteries are simpler and more common.
• Choose the right battery size based on your energy consumption and solar production patterns.
• Check installation certifications and warranties.
• Factor in government policies and potential savings to calculate your return on investment.

Retrofitting battery storage to your existing solar panels is a feasible and effective way to enhance your renewable energy system, save money, and contribute to a greener UK energy grid.