DESNZ records about 1,990 solar PV installations of all sizes across Kingston upon Thames at the end of 2025, with 9.27 MW of capacity between them. That count includes non-domestic systems. DESNZ also notes that many 2025 installations had not yet been assigned to a council area, so the published figure will probably rise. Even so, it means a good number of homes in the borough already have panels. If yours is one of them, the battery question is not “solar or not?” but “what does adding storage to what I have involve?”
This guide answers that for Surbiton: the inverter choice, the grid paperwork, VAT and cost data, and the practical points on the town’s Victorian terraces and station-side flats. For the battery basics in KT5 and KT6, see our Surbiton home battery guide.
Step one: read your inverter’s label
The inverter is the piece of an existing system that decides the route. Inverters typically carry shorter warranties than panels, so on an older system it is worth knowing its age, model and remaining cover before anyone designs around it. There are two common routes.
A separate battery inverter (AC-coupled). The existing solar inverter stays. The battery has its own inverter and is wired in on the household side. This route disturbs least of what already works, and it suits an array whose inverter is healthy.
A hybrid inverter (DC-coupled). The old inverter is replaced by one unit that manages both the panels and the battery. This route makes the most sense when the old inverter is near the end of its life anyway, because you would be paying to replace it before long.
Neither route is right for every house. A quote that does not say which it uses, and why, is missing its most important line.
Step two: the grid paperwork changes
A battery’s inverter counts towards your system’s total. Under ENA EREC G98, type-tested generation up to 16 A per phase (3.68 kW) is notified to the network operator, before commissioning or within 28 days after it. Anything above that needs a G99 application approved before work starts. For reference, a 4 kW inverter draws 17.39 A, just over the G98 line. If your solar inverter is already near that limit, adding a battery is often what tips the system into G99.
UK Power Networks says that where the maximum export after any export limitation is under 5 kW, it approves the application automatically. An export limitation scheme caps what the system can send to the grid, whatever the inverters could produce.
Surbiton’s town centre sits in UK Power Networks’ South Eastern Power Networks area, about 1.5 km from its London Power Networks area, so parts of the town may be on the London network. Both are UK Power Networks licence areas, but check your own address with UKPN’s area checker rather than assuming. If UKPN finds your supply cannot take the extra load, it may need to upgrade it first. UKPN says there is nothing to pay it if no upgrade is needed.
One thing does not change: a standard grid-tied battery shuts down in a power cut. Backup needs a system designed and installed for it.
Step three: your export tariff
Smart Export Guarantee payments depend on an MCS certificate for the installation and a meter that can take half-hourly export readings. Adding a battery changes your system, so tell your export supplier and check the terms before the work, not after. Rates are set by each supplier and change at short notice, which is why we never print one.
What a retrofit battery costs, on published data
The Energy Saving Trust puts home batteries at £1,500 to £10,000, with about £4,600 for a 5 kWh system and a typical home system of perhaps 10 kWh. It also says fitting storage at the same time as panels costs less than a separate visit later. Retrofit is that separate visit, and a quote should show what it adds.
DESNZ’s MCS battery statistics cover batteries fitted to existing homes, and their costs exclude any solar fitted alongside, so they are a closer match for a retrofit:
| Battery size band (2025/26) | Mean cost per kWh | Average size | Average job (our arithmetic) |
|---|---|---|---|
| 1–5.99 kWh | £1,280 | 5.14 kWh | about £6,570 |
| 6–10.99 kWh | £870 | 9.80 kWh | about £8,520 |
Installs in the dataset rose from 24,242 in 2024/25 to 44,033 in 2025/26. These are national averages, not our price. Our guide to how long solar batteries last covers the other side of the sum: the Trust gives a typical lifespan of about 10 to 12 years.
On VAT, HMRC says batteries installed in homes have qualified for the zero rate since 1 February 2024, including when they are added to existing panels. The 0% rate runs until 31 March 2027 and reverts to 5% from 1 April 2027.
Sizing against what your array makes
PVGIS estimates a 4 kWp south-facing array in Surbiton at about 484 kWh in June and 137 kWh in December. In our arithmetic, December is roughly 28% of June. In summer a battery has plenty of surplus to store. In midwinter there is little left over after daytime use. Size to your evening use, not to the roof, as our guide to what size home battery you need explains.
Fitting it in a Surbiton home
The battery goes inside, not on the roof. That matters in the St Andrew’s Square conservation area, where three-storey Victorian Gothic terraces were built between 1876 and 1884. On a retrofit the panels are already up, and the new work is a wall unit and cabling.
Two practical points:
- Mid-terraces with no side access often mean a route through the house or a cupboard near the consumer unit.
- Flats near the station usually need the freeholder’s consent, even for an indoor unit.
Kingston’s 2021 Census shows 60.9% of households own their home and 27.3% rent privately. If you rent, the landlord’s agreement comes first.
If your current array is small, or you are weighing up more panels, our solar panels Surbiton page covers the six local conservation areas. For the wider picture, see solar panels in South West London.
Sources: DESNZ, Renewable electricity by local authority 2014 to 2025 (published 29 September 2026); DESNZ, MCS-certified domestic battery installation statistics (28 May 2026); ENA EREC G98 Issue 2 (10 March 2025); UK Power Networks, Solar and storage: cost, time and what’s involved, and licence boundaries; Ofgem, Smart Export Guarantee; Energy Saving Trust, Battery storage (updated 19 August 2026); HMRC VAT Notice 708/6; PVGIS 5.3 (European Commission JRC), SARAH3 2005–2023, run 15 October 2026; Royal Borough of Kingston upon Thames, St Andrew’s Square conservation area; ONS Census 2021, tenure (Royal Borough of Kingston upon Thames).