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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 £2,495 AC-coupled — written quote before work
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  • 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.

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Wow!!! I have a Givenergy system. The battery stopped charging and depleted fully. Obviously Givenergy went into administration, so I was working with the reseller / installer to get it fixed. They told me they couldn't resolve it and the best they could do was offer me a replAcement at cost, so basically having to buy a new system. I happened to come across STS when searching for how to fix it myself. Ronald has been a god send, within 2 days all is working perfectly and set up correctly. When it comes to experts. He truly is the expert. If you have issues with your Givenergy system and don't know where to go for good help, give him call. 07944 877329. Thanks Ronald, regards Neil W

Neil · Jul 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

My GivEnergy solar and battery system is failing intermittently, GivEnergy is in administration and so is my installer, so it was a relief to get Ron’s expert advice.

Steve Trossell · Jun 2026 Google

My issue was assessed and resolved quickly once the engineer was able to look at the problem. This took a little longer than I had expected (3 days) and keeping the PC on all day/everyday with Sentinel open was a little cumbersome I thought. That said, with little support coming from GivEnergy nowadays it was good to find someone who knew the platform and could resolve my issue.

Terry Hanney · Oct 2026 Google

After 6 months of trying to find someone to help with non functioning Givenergy batteries and inverter, I contacted Ron at STS who remotely sorted the problem within days. Highly recommended.

Francesca Pomlett · Oct 2026 Google

Ron responded very promptly regarding my GivEnergy battery issue, his knowledgeable diagnosis was spot on and resolved the issue on first attempt. Would recommend to any and all.

Simon Hill · May 2026 Trustpilot

Written by · Independent Solar Engineer Last updated

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 (Growatt, SolaX)
✓ Simpler to install — no string rewiring
✓ From £2,495 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 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. Fox ESS's AC1(G2) is an example: an AC-coupled battery inverter with no solar input of its own, added beside your existing solar inverter, which stays in place.

Typical cost: from £2,495 installed, including hardware, circuits, and DNO notification.

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 (Sunsynk, Growatt SPH, SolaX, Fox ESS H1 or KH). 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. Switchgear work depends on your current setup and is quoted in writing before work begins. This is a standard part of any AC coupling installation.

3
DNO notification — G98 or G99

Your installer must tell your Distribution Network Operator (DNO) when a battery is added. If the total stays within 16 A per phase, a G98 notification within 28 days is enough, with no approval. Above that, G99 applies and the DNO has to agree first: a Fast Track answer is due in 10 working days and the standard route can take up to 45 working days. A battery set up to run the home in a power cut (island mode) can't use the Fast Track, so it goes through the standard G99 process. Your installer should handle this. Operating without notifying the DNO technically breaches your grid connection agreement — always confirm the notification 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. A typical wall-mounted battery unit is similar in footprint to a boiler.

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 app or 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 £2,495
✓Battery inverter + storage unit
✓Installation, switchgear, and CT clamp
✓DNO notification (G98 or G99) handled

DC Coupling (replace inverter + add battery)

From £3,495
✓New hybrid solar inverter + battery
✓Installation, switchgear, and rewiring
✓CT clamp + DNO notification (G98 or G99) 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.

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 £2,495.

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 £2,495.

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 across Yorkshire & beyond

We fit retrofit batteries on-site across a wide coverage area from our Leeds base, including Leeds, Bradford, Wakefield, Harrogate, York, Sheffield, Huddersfield, Doncaster, Hull, Barnsley, Scunthorpe, Grimsby, Mansfield, Derby, Nottingham, Manchester, Darlington, and Middlesbrough.

See all areas we cover →
FAQ

Battery retrofit — frequently asked questions

Yes — via AC coupling, which works with any existing solar inverter. You add a separate battery inverter 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. Your installer must tell your network operator when a battery is added: a G98 notification within 28 days if the total stays within 16 A per phase, or a G99 application if it does not, which can take 10 working days on the Fast Track (not open to a battery set up to run the home in a power cut) and up to 45 working days on the standard route. Failure to notify technically breaches your grid connection agreement, so always notify.
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. Two exceptions: GivEnergy Ltd entered administration on 9 April 2026 and no further hardware warranties will be honoured, and Fox ESS claims go through a Local Installer.
No. Battery installations involve high-voltage DC circuits, AC switchgear modifications, and grid connection compliance, so only a qualified electrician (Part P registered) should undertake this work. Improper installation can damage equipment, cause fire risk, or breach your insurance. Always use an accredited MCS installer — they also handle telling your DNO.
AC-coupled battery storage starts from £2,495. DC-coupled retrofits (replacing the inverter and adding a battery) start from £3,495. Costs vary by region, installer, and battery size, and AC coupling is usually cheaper and simpler for existing solar-only systems. Always get written quotes from MCS-accredited installers before committing.
The timing depends on the DNO route rather than the installation. Your installer must tell your DNO when a battery is added: a G98 notification within 28 days if the total stays within 16 A per phase, or a G99 application if it does not, which can take 10 working days on the Fast Track (not open to a battery set up to run the home in a power cut) and up to 45 working days on the standard route. 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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