A terrace roof in Wimbledon, Tooting or Sutton often carries less than 4 kWp of panels. Even a full 4 kWp south-facing array makes about 137 to 140 kWh across December here on PVGIS figures, roughly 4.4 to 4.5 kWh a day (our arithmetic). That small winter number is the right starting point for comparing home batteries in South West London, where so many homes are terraces and flats. This guide compares five brands on that basis, from the manufacturers’ published figures: EnSmart batteries in South West London, Tesla Powerwall, Sigenergy SigenStor, EcoFlow PowerOcean and Fox ESS.
The battery systems in HCE’s own job photos are EnSmart, and EnSmart is the range we fit. For any other brand, ask us and we will confirm in writing how it would be supplied, who installs and commissions it, and what warranty attaches. Nothing below ranks the brands or prices them. The area overview is on solar panels in South West London, and how storage works on battery storage.
What a winter day fills
| Brand | Smallest published step | How it grows |
|---|---|---|
| EcoFlow PowerOcean | 5 kWh pack | 5 kWh steps, to 20 kWh on one single-phase inverter |
| EnSmart SolarAll | 5.12 kWh ELV-W wall pack | 10.24 kWh wall pack; 15 or 20 kWh ELV-F floor packs |
| Fox ESS | 5.18 kWh EP5 | Up to four EP5s, a quoted 20.8 kWh |
| Sigenergy SigenStor | 6.02 kWh module (5.84 kWh usable) | 6.02 or 9.04 kWh modules, one to six per controller |
| Tesla Powerwall 3 | 13.5 kWh unit | 13.5 kWh Expansion units |
PVGIS gives the ten towns we cover about 479 kWh in June at Mitcham, Tooting and Richmond to 484 kWh at Surbiton for the same 4 kWp array, about 16.0 to 16.1 kWh a day (our arithmetic). So on a full-size roof a December day’s output fits inside any of the smallest steps above, while a June day can fill a Powerwall 3. On a smaller terrace roof the figures scale down with the array. A household with modest evening use should model a small modular battery and a single large unit against its own meter readings before choosing either.
Terraces: width, depth and weight
Merton’s housing is 35.7% terraced and only 5.7% detached; Sutton’s is 24.5% terraced and 27.9% semi-detached, and Kingston’s largest type is the semi, at 31.7% of 65,626 households. In a Victorian or Edwardian terrace the realistic spots are an understairs cupboard, a utility space, a rear wall or the side return. Depth decides a hallway or cupboard: Fox ESS gives the EP5 as 147 mm deep, Tesla the Powerwall 3 as 193 mm, and Sigenergy its modules as 265 mm deep and 767 mm wide. Weight decides the carry: 130 kg for a Powerwall 3, 62 or 78 kg per Sigenergy module, about 50.5 kg for an EP5. EnSmart’s ELV-W pack is indoor-only at IP50, which suits an understairs cupboard. EcoFlow’s IP65 enclosure, heating pads and wall-mount option suit a rear wall, though EcoFlow publishes no pack weight. Much of Richmond and Wimbledon is conservation area, so keep any outdoor unit off the street-facing side and ask the council first.
Flats and freeholders
Flats are a large share of the housing here: 36.3% of Kingston’s households live in them, purpose-built flats are 31.3% of Sutton’s, and across the three Tooting wards 54.2% of 20,452 households live in a flat or maisonette. Croydon’s housing needs assessment puts flats at 41% of the borough’s dwellings. UK Power Networks needs the building owner’s permission before solar or storage work starts on a multi-occupied building, so the freeholder’s consent comes before the choice of brand. A converted flat in a house usually has its own supply and meter, so any battery would serve that flat alone and needs a space that is legally yours.
Two UK Power Networks licences
The area straddles London Power Networks, which covers the Wimbledon, Mitcham and Tooting town centres, and South Eastern Power Networks, which covers Kingston, Surbiton, Twickenham, Richmond, Sutton, Carshalton and Croydon. Kingston’s and Richmond’s town centres are within 0.7 km of a boundary, so the postcode decides. The rules are the same on both: up to 16 A per phase (3.68 kW) is a G98 notification within 28 days of commissioning, larger systems need G99 approval first, and UK Power Networks approves automatically where export after any export limitation is under 5 kW. Existing panels count towards the total. On the published line-ups, Sigenergy’s 3.6 kW controller, Fox ESS’s 3.7 kW H1-G2 and a Powerwall 3 set at 3.68 kW are within G98; EnSmart’s 3–6 kW SolarAll-H range spans the line, and for EcoFlow the inverter set-up decides.
Warranties and backup, in plain terms
Every warranty here has an end point. Tesla promises ten years and 80% of capacity for UK installations, on a Powerwall bought from Tesla or a Tesla certified installer. Sigenergy promises ten years to 60% of usable energy or a throughput cap, with an internet connection required. EcoFlow publishes 15 years of daily use until 70% of original capacity, subject to registration and correct installation. Fox ESS gives ten years on EP-series batteries to 70% or a throughput cap, and ten years on the inverter only if it is connected to Fox Cloud within 120 days, otherwise five. EnSmart’s ELV-W datasheet lists five years on the product and ten on performance, and we confirm the exact terms in writing.
Backup is never automatic. Ofgem’s 2024/25 figures show about 11.2 supply interruptions per 100 customers and 10.5 minutes lost per customer on London Power Networks, and about 42.2 and 30.4 on South Eastern. A battery only carries a home through a cut when it is designed for it: Tesla’s Backup Gateway 2, the Sigen Energy Gateway, Fox ESS’s EPS circuit, or an EnSmart or EcoFlow installation specified and wired for backup.
What we install, and what we will confirm
The EnSmart SolarAll cabinets in our job photos are what we fit, sized to the house in front of us. For borough detail, see battery storage in Wimbledon, Kingston upon Thames and Sutton. Ask for a survey, or call 0204 547 1892.
Sources: EnSmart SolarAll-H and ELV datasheets as cited on our EnSmart product page; Tesla Powerwall 3 UK datasheet (2026) and Tesla Powerwall Warranty, European Warranty Region, Rev. 1.16; Sigenergy Battery 6.0/10.0 and Energy Controller (version 20260330) datasheets and Europe warranty (27 May 2025); EcoFlow UK PowerOcean product pages; Fox ESS EP5 datasheet V1.5, H1-G2 datasheet V2.0, UK battery warranty policy V4.5 and inverter warranty policy V2.3; ONS Census 2021, TS044 Accommodation type (Nomis); Croydon Local Housing Needs Assessment (Iceni Projects for LB Croydon, December 2023); PVGIS 5.3, European Commission Joint Research Centre (PVGIS-SARAH3 2005–2023), runs of 15 October 2026; UK Power Networks licence boundaries (December 2024) and Solar and storage: cost, time and what’s involved (read 15 October 2026); NESO GB DNO licence areas (May 2024); Energy Networks Association EREC G98 Issue 2 (10 March 2025); Ofgem, RIIO-2 Electricity Distribution annual report 2024 to 2025, supplementary datafile.