Brentwood Borough Council has already shown what a well-sized array can do on one of its own buildings: panels on the Brentwood Centre now meet 96% of the site’s peak energy demand, and the council plans grant support for a new installation at Seymour Pavilion. Plenty of Brentwood homeowners got there first on a smaller scale. If yours is one of the roofs that went solar a few years ago, without storage, this guide covers the question owners of older arrays ask most: is a battery worth adding now? For the roof itself, from green belt rules to UK Power Networks, see our page on solar panels in Brentwood.
The short answer is often yes, sometimes no, and it depends more on your evening electricity use and the age of your inverter than on the town.
What the borough’s solar count does and does not tell you
DESNZ records about 1,487 solar PV installations of every size across Brentwood borough at the end of 2025, as first published, with 57.31 MW of capacity between them. Two cautions apply. The count covers everything from a house roof to a solar farm, so the capacity figure says little about a typical home array. And DESNZ notes that many 2025 installations could not yet be assigned to a local authority, so borough counts are likely to rise when the figures are revised.
What the count does show is that a battery retrofit in Brentwood is rarely a first-of-its-kind job. Nationally, DESNZ counted 44,033 MCS-registered battery installations in existing homes in 2025/26, up 81.6% from 24,242 the year before. Those are statistics in development, but adding storage to a lived-in house is now routine.
Check the old array before you buy anything
Before talking about batteries, look at what is already on the roof. Three things matter.
The inverter. Panels are designed to last 25 to 30 years, but inverters typically carry shorter warranties. If yours is already old, replacing it with a hybrid inverter that runs panels and battery together may be the cleaner job.
The array size. A small array on a house that is busy in the daytime leaves little surplus to store. A larger one on a house that empties during the working day leaves plenty.
The house. Across Brentwood borough, 30.3% of households live in detached houses and 31.9% in semis, and 71.9% own their home (Census 2021), so a garage or utility room within reach of the consumer unit is often available and the decision is usually yours. In the town itself 29.4% of households live in flats or maisonettes, where anything fixed to shared fabric needs the freeholder’s agreement first.
Two ways to join a battery to a Brentwood array
An AC-coupled battery comes with its own inverter and connects alongside the existing solar inverter, which stays in place. It is usually the simpler retrofit and leaves the original array’s wiring alone. A hybrid inverter replaces the existing one and handles panels and battery together. The battery systems we fit are EnSmart and Hanchu, and which design suits your house depends on the age of the kit already installed and where the inverter and consumer unit sit. Our post on how long solar batteries last covers the warranty side.
Size it to a summer evening, not to December
PVGIS 5.3, the European Commission’s solar calculator, puts a 4 kWp south-facing array at the Brentwood town-centre point at about 497 kWh in June and about 498 kWh in July, against about 140 kWh in December and 159 kWh in January. On our arithmetic, December is about 28% of June. For scale, Ofgem’s typical domestic consumption value from 1 July 2026 is 2,500 kWh a year.
That gap is why a retrofit battery is sized to the evening load on a long summer day, when an existing array runs well ahead of what the house uses and exports the rest. In December there is little surplus to keep, and no battery changes that. The Energy Saving Trust says there is no exact formula for sizing, and that a typical home system might be 10 kWh; your own usage decides. Our guide to what size home battery you need explains how to check the size on a quote.
The UK Power Networks paperwork
Adding a battery changes what your home can put onto the network, so the network operator has to know. Brentwood’s town centre sits in UK Power Networks’ Eastern Power Networks area. If the combined system stays within 16 A per phase (3.68 kW), the installer notifies UKPN under G98, before commissioning or within 28 days after it. If the battery takes the total above that line, a G99 application has to be approved before the work starts. UKPN says it automatically approves applications where the maximum export, after any export limitation, is under 5 kW, and if no supply upgrade is needed there is nothing for you to pay it. The installer deals with UKPN on your behalf.
Cost, VAT and when to say no
The Energy Saving Trust puts home batteries at £1,500 to £10,000, with a 5 kWh system at around £4,600 and a lifespan of about 10 to 12 years. It also says fitting storage at the same time as panels costs less than a separate visit later, which is the honest drawback of any retrofit: you are paying for a second visit. On tax, HMRC zero-rates residential battery installations until 31 March 2027, whether the battery goes in with panels or on its own, and the rate reverts to 5% from 1 April 2027.
Skip the battery when the array is small and the house is occupied all day, when evening use is low, or when the old wiring would need so much work that the cost stacks up. In Brentwood the median detached house and the median semi each score 64 on the EPC scale, band D, so for some homes insulation is the better next step. And a standard battery does not provide backup in a power cut unless backup is designed in.
Next steps
If a battery is on your list, our page on battery storage in Brentwood covers sizing and the network in more detail, and solar panels in Essex gives the county picture, including the Warm Homes: Local Grant route. When you would like a survey that looks at the old array as well as the new battery, use our contact page.
Sources: Brentwood Borough Council, Climate Emergency; DESNZ, Renewable electricity by local authority 2014 to 2025 (published 29 September 2026); DESNZ, MCS-certified domestic battery installation statistics (28 May 2026); ONS Census 2021, TS044 and TS054 (Brentwood) and Towns and cities, characteristics of built-up areas (Brentwood BUA); ONS, Median energy efficiency score, England and Wales (records to March 2025); PVGIS 5.3, European Commission Joint Research Centre, PVGIS-SARAH3 2005–2023, run 15 October 2026; Ofgem, typical domestic consumption values (from 1 July 2026) and Smart Export Guarantee; UK Power Networks, Licence Boundaries open dataset and Solar panels and energy storage: cost, time and what’s involved; Energy Networks Association, EREC G98 Issue 2 (10 March 2025); Energy Saving Trust, Battery storage (updated 19 August 2026); HMRC VAT Notice 708/6.