If there is an electric car in your Wimbledon household, a home battery can look like the obvious companion: one big battery feeding another. In practice the two are sized for different jobs, and getting that wrong is an expensive mistake. The car’s battery is sized for driving; a home battery is sized for the house’s evenings. This guide explains why, using Merton’s own figures, and where a home battery does earn a place alongside a car.
For fitting the charger itself, from Raynes Park semis with a drive to Grid terraces without one, see our Wimbledon EV charger installation page. If you already have panels and are thinking about adding storage, our earlier post on adding a battery to existing solar in Wimbledon covers the retrofit questions.
Two different sizes of battery
For a Wimbledon household weighing both, the Energy Saving Trust’s figures are the place to start: it says a typical home battery system might be 10 kWh, and that a 5 kWh system costs around £4,600. Taking a 60 kWh charge as an illustration of a car, the typical home battery holds about a sixth of it (our arithmetic). Those numbers already explain most of the answer: a home battery large enough to fill a car would be several times the size the Trust calls typical, and priced accordingly.
Merton’s car numbers make the question a common one. DVLA records 5,503 privately kept plug-in vehicles across the borough at the end of June 2026, up from 4,487 a year earlier. That is 1,016 more vehicles in twelve months, and each one comes with a decision about how it is charged.
What a Wimbledon house uses
A home battery is sized against the house. Ofgem’s Typical Domestic Consumption Value from 1 July 2026 is 2,500 kWh a year, which averages about 6.8 kWh a day (our arithmetic). Only part of that falls in the evening, when a battery is most useful, and a 10 kWh battery already holds more than the whole of that average day (our arithmetic) before a car is involved. A Wimbledon Village house with more rooms and appliances will use more, a flat less; the Trust says there is no exact sizing formula, which is why we work from your own bills at the survey.
A 7 kW charger would empty it
Picture a Raynes Park drive with both. A 7 kW charger draws 32 A and delivers roughly 7 kWh an hour. Connected to a full 10 kWh home battery, it would draw the battery flat in under an hour and a half (our arithmetic), having added only a sixth of a 60 kWh charge. The house would then face its own evening with an empty battery and buy from the grid at whatever the tariff charges.
That is why, in most Wimbledon homes with both, the car charges overnight. Every new home chargepoint sold in Great Britain since 30 June 2022 has had to be smart, with default charging hours outside weekday peaks, so the charger schedules itself into the cheaper part of the night while the battery is kept for the house.
Where a battery does help an EV household in Merton
In a Merton EV household, a battery earns its place, if it does, through the house’s evening use, and such a household may already have the tariff that makes that work. If your tariff has a cheaper overnight rate for the car, a battery can charge on the same rate and cover the dearer evening, instead of the house buying at peak.
Panels add a summer layer. PVGIS gives a 4 kWp south-facing array in Wimbledon about 480 kWh in June, roughly 16.0 kWh a day, and about 140 kWh in December, roughly 4.5 kWh a day (our arithmetic). On a June weekend with the car at home, surplus can go into the car; on a weekday, with the car at work, a battery can hold some of it for the evening. In December there is little to spare, so the battery runs on the overnight rate. DESNZ records about 2,398 solar PV installations of all sizes across Merton at the end of 2025, so many households already have the panels and are asking this question.
For the battery itself, where it goes and how it is sized, see our page on battery storage in Wimbledon.
Grid terraces and lamp columns
Terraces are 35.7% of Merton’s households, and in the Victorian Grid many have no drive. Merton Council does not currently permit pavement channels or gullies for charging cables, and its answer for those streets is lamp-column charging: 90 chargers in 2021 and 530 more in 2023. If your car charges at a lamp column, a home battery does nothing for the car at all. It may still suit the house, judged on the house’s own use. Flats are 37.6% of the borough’s homes, and there a battery and a charger both need the freeholder’s written consent first.
Grants in Merton follow the same split. Owner-occupiers of houses get no OZEV chargepoint grant. Renters and people who own and live in a flat can claim 75% of the cost up to £500 per socket with private off-street or allocated parking; the claim must be made through an OZEV-authorised installer, so tell us your situation at the quote stage. Our guide to the EV chargepoint grant has the rules.
Tax, paperwork and power cuts
The two are taxed differently: a residential battery carries 0% VAT until 31 March 2027, then 5%, while a home charger installation is standard-rated at 20%. Ask for them on separate lines. Wimbledon is in UK Power Networks’ London Power Networks area, about 3.7 km from its South Eastern network, and the installer notifies UKPN of both; a battery above 16 A per phase needs a G99 application approved before work starts. Neither a battery nor a charger keeps the house running in a power cut by default. The kit we fit is on our home EV charger installation guide.
Sources: Energy Saving Trust, Battery storage (last updated 19 August 2026); Ofgem, Typical Domestic Consumption Values (from 1 July 2026); DfT and DVLA, VEH0142, privately kept, end of June 2026 and 2025 (published 23 September 2026); European Commission JRC, PVGIS 5.3, 4 kWp, 35°, due south, 14% losses (run 15 October 2026); DESNZ, Renewable electricity by local authority 2014 to 2025 (published 29 September 2026); ONS Census 2021, TS044 and TS054 (Merton); Merton Council, EV charging (read 19 October 2026): https://www.merton.gov.uk/streets-parking-transport/ev/charging; Electric Vehicles (Smart Charge Points) Regulations 2021; HMRC, VAT Notice 708/6; ENA, EREC G98 Issue 2; GOV.UK, Changes to electric vehicle chargepoint grant schemes from 1 April 2026 (updated 7 July 2026); UK Power Networks, licence boundaries (December 2024).