Add battery storage to existing solar panels
You have a solar-only system and want to add battery storage to use more of your generation and reduce grid dependence. Before you commit to a battery retrofit, you need to understand coupling options, inverter compatibility, costs, and DNO requirements.
For most existing solar-only systems, AC coupling is the answer — it works with any inverter, costs £2,995–7,000, and does not require replacing your current setup. This independent guide covers everything you need to make the right call.
A solar system health check includes an assessment of your current inverter, generation profile, and the best battery retrofit option for your setup — whether AC coupling, DC coupling, or a different approach entirely.
Book a System Health Check → What's includedThe battery retrofit decision: AC or DC coupling?
For most solar-only systems, the choice comes down to whether you keep your existing inverter (AC coupling) or replace it with a hybrid model (DC coupling).
In most cases, start with AC coupling. It works with any existing solar inverter, is cheaper, and is simpler to install. Only consider DC coupling if your current inverter is already a hybrid model that supports battery retrofit, or if you are planning to replace the inverter for other reasons and want to combine the work.
AC coupling vs DC coupling — how they work
AC Coupling — how it works
In AC coupling, you install a battery inverter (such as a GivEnergy AIO unit) alongside your existing solar inverter. Both are connected to the AC side of your installation — they each export to your house and grid independently.
Charging: The battery charges from grid (during cheap overnight tariff periods) or from solar excess (when generation exceeds household demand). The battery inverter has its own CT clamp monitoring import/export.
Discharging: When household demand exceeds solar generation, the battery discharges to cover the deficit — reducing grid import.
Compatibility: Works with every solar inverter on the market. No changes to your solar array or existing inverter required.
Typical cost: £2,995–7,000 installed for 5–10 kWh including hardware, circuits, and DNO variation.
DC Coupling — how it works
In DC coupling, the battery connects directly to the DC bus of a hybrid solar inverter. The same unit manages solar generation, battery charging, house loads, and export — no separate battery inverter needed.
Efficiency: Solar energy flows DC-to-DC into the battery without the AC conversion step — approximately 2–5% more efficient than AC coupling.
Control: The hybrid inverter manages all energy flows in real time — smarter than having two independent inverters.
Compatibility: Requires replacing your existing string inverter with a hybrid model (GivEnergy, Sunsynk, Growatt SPH, SolaX, Fox ESS). Not compatible with standard string inverters.
Typical cost: £7,000–12,000 installed — includes the inverter replacement cost.
Is your current inverter compatible with DC coupling?
DC coupling requires a hybrid inverter with a battery port. Most older string inverters do not have this. Check your inverter against the list below.
Fronius: Gen24, Symo Hybrid series
SMA: Sunny Boy Storage SM4/SM5/SM6
SolaX: Hybrid G4, X3 Hybrid
Growatt: SPH, SPA series (with ARM firmware)
GivEnergy: AIO (already hybrid — has battery)
Sunsynk: Hybrid 3.6–8 kW
Fronius Symo: Non-hybrid series
SMA Sunny Boy: Standard series
SolaX Mono/Triple: Non-hybrid models
Growatt ShineWay: String inverter
Sungrow SG5K/SG8K: Standard string
Most pre-2018 inverters
How to check: Find your inverter's exact model number (it's on a label on the unit). Search the manufacturer's website for that model. If there is no battery port or battery compatibility listed, it is a string inverter — AC coupling is your option. If in doubt, a system health check includes an inverter compatibility assessment.
Practical considerations before retrofitting
Your current solar system uses a CT clamp to measure house consumption. When you add a battery, the clamp position may need changing so the battery inverter correctly measures what it should charge from or discharge to. In AC coupling, the battery inverter typically has its own CT — your installer will confirm the correct position during survey. In DC coupling with inverter replacement, the CT is usually repositioned as part of the new installation.
AC coupling requires new circuits from the battery inverter to your consumer unit — new MCBs and typically a dedicated battery isolation switch. Older consumer units may need upgrading to accommodate additional circuits. Budget £500–1,500 for switchgear work depending on your current setup. This is a standard part of any AC coupling installation.
Adding a battery changes your registered installation and requires a G99 variation form to your network operator. This is simpler than a full G99 application and is usually approved automatically within 2–4 weeks. Your installer should handle this. Operating without notifying the DNO technically breaches your grid connection agreement — always confirm the variation has been submitted.
Battery units and inverters are wall-mounted or floor-standing. The battery unit needs clear wall space in a utility room or garage with adequate ventilation and no risk of temperature extremes. For AC coupling, both the existing solar inverter and the new battery inverter must be accessible. Typical GivEnergy AIO units are approximately 600 × 400 × 220mm — similar to a boiler in footprint.
To benefit from cheap overnight electricity (e.g., Octopus Go, Agile), the battery inverter must be configured with a timed charge window that matches your tariff's cheap rate hours. This is done in the battery's monitoring portal (e.g., GivEnergy portal). Your installer should configure this as part of commissioning. If they don't, you will be charging at standard rate rather than taking advantage of time-of-use pricing.
Realistic costs for battery retrofits in 2026
Battery prices have fallen significantly. These are realistic current figures — always get written quotes from MCS-accredited installers.
AC Coupling (5–10 kWh)
DC Coupling (Replace inverter + battery)
Notes: Costs vary by region — London and the South-East typically run higher. Always get 2–3 written quotes from MCS-accredited installers. Battery size affects cost — 5 kWh is cheaper than 10 kWh. Finance options are available from some installers. These are estimates only — confirmed written quotes are essential before committing.
Common AC coupling battery options for UK retrofits
These systems are commonly used in the UK for adding battery storage to existing solar-only systems.
Battery inverter + storage unit combined in one package. Very popular for UK retrofits. Smart charge scheduling supports Octopus Go, Agile, and other time-of-use tariffs. Available in 2.6 kW / 5.0 kW with up to 19.2 kWh storage. Excellent monitoring portal. Typical installed cost: £2,995–6,500. See the GivEnergy support hub for setup guides.
Sunsynk hybrid inverters can be used for AC coupling in a retrofit scenario. Excellent for time-of-use tariff management. Supports Pylontech and other compatible batteries. UK-based support. Typical installed cost: £2,995–6,000.
Growatt hybrid units support AC coupling. Available in 3 kW, 5 kW, 6 kW. Supports ShinePhone monitoring and time-of-use scheduling. Compatible Growatt GBLI batteries. Typical installed cost: £3,500–5,500.
Related guides
Already have a battery and want to expand? This guide covers adding a second module to an existing hybrid system.
Adding a battery opens the door to EPS backup. What enabling emergency power supply involves.
If DC coupling is your preference, inverter replacement with a hybrid model is the first step.
Setup guides, portal configuration, monitoring setup, and tariff optimisation for GivEnergy systems.
Battery retrofit — frequently asked questions
Yes — via AC coupling, which works with any existing solar inverter. You add a separate battery inverter (such as GivEnergy AIO) alongside the existing solar inverter. DC coupling, which connects the battery directly to the solar inverter's DC bus, only works if your existing inverter is a hybrid model. Most older string inverters only support AC coupling.
AC coupling adds a battery inverter alongside your existing solar inverter — both operate independently on the AC side of your system. It works with any existing inverter. DC coupling connects the battery directly to the DC bus of a hybrid inverter — more efficient but requires replacing your existing string inverter with a hybrid model. For most solar-only systems, AC coupling is the recommended starting point.
Not with AC coupling — you keep your existing solar inverter and add a battery inverter alongside it. With DC coupling, you do need to replace your string inverter with a hybrid model (which is more expensive). For most existing systems, AC coupling is the simpler and cheaper option.
Yes. Submit a G99 variation form to your network operator. Most variations are approved automatically within 2–4 weeks. Your installer should handle this. Failure to notify technically breaches your grid connection agreement, though enforcement is rare. Always notify — it is required by law and the process is straightforward.
In AC coupling, no — the battery is independent and your solar inverter warranty is unaffected. In DC coupling, you are replacing the solar inverter, so the old warranty ends and you receive a new warranty on the hybrid inverter (typically 10 years). Check with your original installer or manufacturer if in doubt before proceeding.
No. Battery installations involve high-voltage DC circuits, AC switchgear modifications, and grid connection compliance. Only a qualified electrician (Part P certified) should undertake this work. Improper installation can damage equipment, cause fire risk, or breach your insurance. Always use an accredited MCS installer — they are also required for the G99 DNO variation process.
AC-coupled battery systems cost £2,995–7,000 installed for 5–10 kWh of storage. DC-coupled retrofits (replacing inverter + adding battery) cost £7,000–12,000. Costs vary by region, installer, and battery size. AC coupling is usually cheaper and simpler for existing solar-only systems. Always get written quotes from MCS-accredited installers before committing.
Ready to explore battery retrofit options?
A solar system health check assesses your current inverter, generation profile, consumption patterns, and roof/wall space — then recommends the best battery retrofit approach for your situation. We explain the trade-offs between AC and DC coupling and provide a realistic cost estimate before you commit.