Excellent response to diagnose a problem on our SolarEdge installation. Kept us informed at every step. Diagnosis quickly completed and solution implemented.
Les Bennett · May 2026
System upgrade · Information guide
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.
from £2,995 AC-coupled — written quote before work
- AC coupling works with most systems
- Not all inverters support DC coupling
- DNO notification required
Unsure if your system is compatible?
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 CheckWhat's includedWhat a fantastic service. Had my fault diagnosed within minutes and actually managed to resolve the issue remotely within a few minutes more. This guy is like a “Solar Batman” helping consumers fix their problems using his extensive industry knowledge and expertise. Outstanding service. Thank you so much.
Andrew Palmer · May 2026
After recently changing my fuse board the ct clamp broke, this meant my inverter was not communicating properly with my GivEnergy system. After several people letting me down, finally got put in touch with Ron. He came out within 24hours & resolved the fault within an hour, no fuse just got on with it. Work was tidy & arrived when he said he would. Ron followed up a few days later to confirm all was still good, great service from all involved.
Mr Paddy · Jul 2026 Trustpilot
Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them
Dennis Brown · May 2026
After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.
Keith Ballard · Apr 2026
A really big thank you to Ron and his team, he has vast amounts of knowledge and got my system back up and running, also good to get on with. I was absolutely lost as to know what to do, no help from installer and somehow came across Ron and am I glad I did. I would definitely definitely recommend him to anyone who has faults with there solar system, any make I would say. Thanks again Ron a pleasure meeting you.
D R · Jun 2026 Google
The 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).
AC Coupling — recommended for most
✓ Works with any existing solar inverter
✓ Add a battery inverter (GivEnergy AIO, Growatt, SolaX)
✓ Simpler to install — no string rewiring
✓ From £2,995 typical cost
✗ Slightly less efficient — ~5% conversion losses
✗ Two separate monitoring portals
DC Coupling — if hybrid inverter supported
✓ More efficient — direct solar to battery
✓ Unified monitoring portal for solar + battery
✓ EPS backup power typically included
✗ Must replace existing inverter with hybrid
✗ From £3,495 total cost
✗ DC string compatibility must be checked
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: from £2,995 installed, 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: from £3,495 installed, including the inverter replacement.
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.
Hybrid inverters — DC coupling possible
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
String inverters — AC coupling only
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
1
CT clamp repositioning
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.
2
Consumer unit and switchgear
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.
3
DNO notification — G99 variation
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.
4
Space and wall mounting
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.
5
Monitoring setup and tariff configuration
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
From £2,995
✓Battery inverter + storage unit
✓Installation, switchgear, and CT clamp
✓DNO G99 variation handled
DC Coupling (replace inverter + add battery)
From £3,495
✓New hybrid solar inverter + battery
✓Installation, switchgear, and rewiring
✓CT clamp + DNO G99 variation handled
Notes: Costs vary by region — London and the South-East typically run higher. Always get 2–3 written quotes from MCS-accredited installers. 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.
GivEnergy All-in-One (AIO)
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: from £2,995. See the GivEnergy support hub for setup guides.
Sunsynk Hybrid
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: from £2,995.
Growatt SPH / SPA series
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: from £2,995.
Related guides
Add an extra battery
Already have a battery and want to expand? This guide covers adding a second module to an existing hybrid system.
EPS / backup power installation
Adding a battery opens the door to EPS backup. What enabling emergency power supply involves.
Inverter replacement guide
If DC coupling is your preference, inverter replacement with a hybrid model is the first step.
GivEnergy support hub
Setup guides, portal configuration, monitoring setup, and tariff optimisation for GivEnergy systems.
Battery retrofits in South Wales
STS has a locally based engineer in Cardiff for battery retrofit surveys and installs. Swansea and Newport are covered from the Cardiff base — roughly 40 minutes and 20 minutes away on the M4 respectively.
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 storage starts from £2,995. DC-coupled retrofits (replacing the inverter and adding a battery) start from £3,495. 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.
Allow 2–4 weeks end to end; most of that is DNO paperwork rather than installation. Adding a battery requires a G99 variation form to your network operator, which is usually approved automatically within 2–4 weeks, and your installer should handle the submission. The on-site work itself is a single day for an AC-coupled installation, where the battery inverter is fitted alongside your existing solar inverter. DC-coupled retrofits, which replace your existing inverter with a hybrid model, are completed as one combined installation.
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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.
- AC and DC coupling options assessed
- Realistic cost estimate provided before any commitment
- Inverter compatibility confirmed before any commitment
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