Adding a battery after solar install

Retrofitting a battery is possible on most systems, but compatibility matters. The easiest retrofit is a DC-coupled battery that connects directly to your existing inverter. AC-coupled batteries work with any inverter but are less efficient.

Compatibility by inverter brand: Sungrow inverters work natively with Sungrow SBR/SBH batteries. Huawei inverters connect to Huawei LUNA batteries. SolarEdge pairs with the SolarEdge Home Battery or LG RESU. Other string inverters may need an AC-coupled solution.

Sizing: A 5 kWh battery covers a typical Irish home's evening load (7pm–11pm). 10 kWh is better if you charge an EV overnight or have high evening usage. More than 10 kWh rarely pays back unless you're doing tariff arbitrage.

Cost: Expect €3,000–€6,000 for a 5–10 kWh battery installed. SEAI gives a €600 grant for a battery of 5 kWh or more if your home was built and occupied before 2025. Get the grant offer before it is installed, use an SEAI-registered solar PV contractor, and expect a BER after the work. Check VAT with your installer: 0% applies when a battery is installed with solar panels. Get at least two quotes and check the installer is qualified and insured.