Yes. Many homeowners can add battery storage to an existing solar PV system without replacing the current solar inverter. An AC-coupled battery is often the retrofit route because it connects storage on the AC side of the system rather than requiring the existing PV array to be moved onto a new hybrid inverter.
The important caveat is that AC-coupled does not mean universally compatible. Before choosing a battery, separate four questions that are often mixed together: the electrical architecture, Feed-in Tariff (FIT) or Smart Export Guarantee (SEG) payment metering, the Distribution Network Operator (DNO) connection route, and the exact product configuration.
If you want the basics first, see how solar battery storage works from daytime generation to evening use.
Can you add a battery to existing solar panels without changing the inverter?
In short
Often, yes. An AC-coupled battery can let the existing PV inverter remain in service, but the battery model, metering, household electrical setup, FIT or SEG position and DNO connection route still need to be checked for the actual installation.
If the existing solar inverter is staying in service and the proposed battery has its own AC-side power-conversion and control arrangement, there may be no need to replace the solar inverter simply to add storage. That is one reason AC coupling is commonly considered for existing-solar retrofits.
What can stop that plan is not the label “AC-coupled” itself. A specific combination may still be unsuitable because of inverter or meter requirements, phase arrangement, control behaviour, grid-connection conditions, FIT or SEG metering, or the way backup would need to be designed.
How an AC-coupled battery works with an existing solar system
In an AC-coupled retrofit, the existing solar PV system can continue doing its original job while the battery system is added on the household AC side. This avoids having to connect the existing PV strings directly to a new hybrid inverter, but it does not remove the need for system-level checks.
What stays in place
The solar panels continue producing DC electricity and the existing PV inverter continues converting that electricity to AC for the home and grid, subject to its existing settings and connection arrangements.
Existing solar path: Solar panels → existing PV inverter → household AC
What the new battery system adds
The battery system adds its own storage, power electronics and control or measurement arrangement on the AC side. Depending on the approved design, it may use an energy meter or current-transformer (CT) measurement to understand household import, export or load and decide when to charge or discharge.
Battery path: Battery system ↔ household AC
These two lines are a functional explanation, not a universal wiring diagram. The actual consumer-unit connections, protection, metering and control layout must match the proposed equipment and the site.
AC-coupled does not mean compatible with every inverter
AC coupling removes the need for the battery and existing PV array to share one direct-PV or DC-side architecture. It does not prove that every battery will work correctly with every inverter, meter, phase arrangement or control configuration.
What to check by make, model and configuration
Before anyone confirms compatibility, give the supplier or installer the information needed to check the exact configuration:
- Your existing PV inverter manufacturer and exact model.
- Its rated AC output.
- The proposed battery and metering model.
- The approved energy-meter or CT arrangement.
- Whether the battery can charge from the grid or export to it.
- Any documented firmware or control requirements.
- Whether the supply and proposed equipment are single-phase or three-phase, and the intended phase configuration.
- Whether power-cut backup is required.
- The proposed installation and network-connection architecture.
A compatibility table built from assumptions is not a substitute for model-specific evidence. If a manufacturer has not approved a named inverter or microinverter configuration, treat it as unconfirmed until the appropriate product or installation documentation supports it.
When replacing the existing solar inverter may make more sense
Keeping the existing inverter is not automatically the best choice. A redesign is worth comparing if the current inverter is already known to need replacement, the chosen battery requires another architecture, the proposed configuration cannot be supported, the solar system is being redesigned anyway, or a required backup function needs a materially different topology.
If you have a legacy Feed-in Tariff, check the metering before changing anything
Adding storage does not automatically cancel Feed-in Tariff (FIT) payments, but neither should you assume every FIT payment is unaffected. The outcome depends on what is being measured and how electricity can flow through the new system. Ofgem’s current co-location guidance for generators explains how storage can sit alongside a FIT installation where the scheme requirements continue to be met.
You must also tell your FIT licensee when battery storage is connected to the accredited installation. Ofgem’s FIT generator guidance says generation and, where relevant, export must remain accurately measurable for the corresponding payments.
FIT generation payments and export payments are different
FIT generation payments relate to electricity generated by the accredited installation. FIT export payments relate to qualifying electricity exported from that installation. A battery retrofit therefore has to preserve the measurement needed for the payment you receive; the presence of a battery on its own is not the deciding factor.
Deemed export and metered export need different checks
Do not hard-code a single deemed-export percentage into a retrofit decision. Ofgem’s current generator guidance describes deemed export as a percentage of generation that is set each year.
Why grid charging and battery export can change the metering question
If a battery can charge from the grid and later export, electricity from different sources can pass through the same household system. That makes source attribution important. For FIT metered export, the relevant meter must still support payment for qualifying export from the accredited installation rather than unrelated electricity. Ofgem’s co-location guidance gives configuration examples for this distinction.
Ofgem’s current co-location guidance says the notification should include an updated single-line or schematic diagram showing how electricity from the installation reaches the storage system and the metering arrangements in place. Additional meter evidence may be required for some configurations.
What changes if you use the Smart Export Guarantee?
The Smart Export Guarantee (SEG) is a Great Britain scheme, not a single UK-wide export arrangement. Ofgem says eligible FIT installations can also be eligible for SEG where the required export or smart metering can take half-hourly measurements, but you cannot receive FIT export payments and SEG payments for the same electricity. See Ofgem’s current FIT scheme-closure guidance.
SEG payments are based on measured export and SEG licensees set their own commercial rates and terms. If co-located storage can also charge from the grid, the treatment of later battery export can depend on whether qualifying export can be identified and on the licensee’s terms. Ofgem’s co-location guidance should be checked before assuming all battery-originated export will be paid.
A SMETS2 meter is therefore not a universal shorthand for every SEG case. The relevant question is whether the approved export or smart-meter arrangement meets the measurement and supplier requirements for the export contract you intend to use.
Do you need to contact the DNO when adding battery storage?
The network connection route must be reassessed when storage is added to an existing grid-connected PV installation. In Great Britain, the answer depends on the aggregate generating-and-storage configuration and the applicable connection procedure, not on the battery’s capacity in kWh.
Why 3.68 kW is not the whole decision rule
In Great Britain, ENA Engineering Recommendation G98 includes electricity storage and defines its single-premises microgeneration route around aggregate Registered Capacity of no more than 16 A per phase. At 230 V on a single-phase connection, 16 A corresponds to 3.68 kW.
That does not mean “3.68 kW or less equals G98, anything above equals a standard G99 application” in every retrofit. Current ENA Engineering Recommendation G99 Issue 1 Amendment 9 includes Small Generation Installation procedures for qualifying combinations of existing or new generation and electricity storage. The installer and DNO should confirm which route applies to the actual system.
Where G98, G99 and G100 fit
G99 covers larger or otherwise applicable grid-connected generation and storage arrangements and includes Small Generation Installation procedures for qualifying systems. The appropriate procedure depends on the capacities, capabilities and control equipment in the proposed installation, so it should be confirmed for the actual PV-and-storage configuration.
ENA Engineering Recommendation G100 Issue 2 Amendment 2 covers Customer Export or Import Limitation Schemes. A G100-compliant limitation scheme can form part of an accepted connection design, but it does not remove the need to follow the applicable DNO process.
Jurisdiction matters: these G98/G99 statements describe the Great Britain framework. Northern Ireland uses separate G98/NI and G99/NI arrangements, so the GB route should not be applied there unchanged.
Which meters and CTs does an AC-coupled retrofit need?
There are two different measurement jobs that are easy to confuse. A battery-control meter or CT helps the storage system decide what to do. FIT or SEG payment metering establishes the generation or export used for scheme or supplier payments. They are not automatically the same device or the same measurement point.
Battery control measurement
An AC-coupled battery may use a compatible energy meter or CT arrangement to understand household power flow. For the Sunpura S2400 AC, the approved product information says the datasheet describes a dual-CT meter for capturing third-party inverter data. That does not establish which third-party inverter types are supported or the exact metering topology; those details still need the appropriate installation or accessory documentation.
FIT and SEG payment measurement
A generation meter, export meter or supplier smart-meter arrangement used for FIT or SEG has a different purpose: it supports scheme or settlement measurement. Do not assume the battery’s “smart meter”, energy meter or CT is automatically the meter that your FIT licensee or SEG licensee uses for payment.
Existing-solar battery retrofit checklist: what to confirm before you buy
The fastest way to get a useful compatibility answer is to provide evidence about the existing installation rather than asking whether a battery “works with solar” in general.
Before choosing a battery, record:
Choose the acceptable system architecture first, then confirm the battery model.
Where the Sunpura S2400 AC fits
The Sunpura S2400 AC is positioned as an AC-coupled storage option for homes with existing solar. Its suitability still depends on the actual inverter, metering, household electrical setup and grid-connection configuration.
Existing-solar option
Sunpura S2400 AC
A configuration-dependent AC-coupled option for existing-solar systems. Confirm the actual inverter, meter or CT arrangement, household electrical setup and network route before treating it as suitable for a specific home.
