Hertsmere’s solar count is bigger than its rooftops. DESNZ records 1,374 solar PV installations across the borough at the end of 2025, with 20.04 MW of capacity, and that figure covers every size, from a semi’s roof to a solar farm. Hertsmere’s own climate strategy lists two 5 MW installations at Potters Bar, running since 2017, among four large sites that hold 16 MW of the borough’s 21 MW of renewable electricity capacity. Most of the capacity sits in a few big sites; most of the installations are smaller.
If one of the smaller ones is on your Potters Bar roof, the sensible question is whether a battery can be added now. Usually it can. This guide sets out how, what changes on paper, and what to have ready. For the battery side in general, our page on home batteries in Potters Bar covers sizing, placement and the network.
What the Hertsmere count does and does not tell you
DESNZ’s figure is local-authority-wide and counts installations of every size, so it is not a count of homes and not a count of batteries. DESNZ also notes that many 2025 installations could not yet be assigned to a council area when the figures were first published, so the Hertsmere count is likely to rise in later editions. What it does show is that solar is established across the borough. For an array already on a Potters Bar roof, you also have something no model can match: your own generation readings.
Two ways to add storage to an array you already have
The first route keeps your existing solar inverter and adds a battery with its own inverter alongside it. This is often called AC coupling. The second route replaces the existing inverter with a hybrid inverter that runs the panels and the battery together; EnSmart’s SolarAll-H, the kit in our own installation photographs, is one. Which suits a Potters Bar home depends on the age and model of the inverter already there, how much life it has left, and how far the battery would sit from it.
The connection paperwork leans on the Energy Networks Association’s type-test register, which records compliance per model and firmware version, not per manufacturer. So the entry for each unit going on your Potters Bar wall, old inverter included, is checked before the application goes in.
The network paperwork changes
Adding a battery adds inverter capacity, and the network operator cares about the total. The Potters Bar town-centre point sits in UK Power Networks’ Eastern Power Networks area. Under the ENA’s G98 rule, type-tested generation up to 16 A per phase (3.68 kW) is notified, before commissioning or within 28 days. Above that, a G99 application must be approved before the work starts. An array that went in under G98 can cross the line once a battery inverter sits beside it. UK Power Networks automatically approves an application where the maximum export, after any export limitation, is under 5 kW, and an export limit is one way to keep a retrofit under that figure. The installer handles it all.
Certificates and export payments
Keep the existing array’s MCS certificate and electrical certificate. A Smart Export Guarantee tariff needs an MCS certificate and a meter capable of half-hourly export readings. Rates are set by each supplier, must be above zero under Ofgem’s rules and change at short notice, so we never print one. Before the battery goes in, ask your supplier how it treats exports from a system with storage.
Cost, timing and lifespan
The Energy Saving Trust puts home storage between £1,500 and £10,000, with a 5 kWh system around £4,600 and a typical home system at 10 kWh. It also says fitting storage at the same time as panels costs less than a separate visit later, so a retrofit gives up that saving. It gives a battery’s typical lifespan as about 10 to 12 years. Our guide to how long solar batteries last covers warranties and design life. A battery added on its own carries 0% VAT until 31 March 2027, the same as one fitted with panels, then 5% from 1 April 2027.
Where it goes in a Potters Bar semi
Potters Bar is a town of semis. In the built-up area, 46.5% of households live in semi-detached houses and 17.7% in detached ones, and in Furzefield ward the semi share reaches 61.6%. In Parkfield, 32.9% of households live in detached houses. A garage or utility room is often the obvious home for a battery. EnSmart’s wall-mounted ELV-W battery is rated IP50, indoor only, while its floor-standing ELV-F packs are IP55 and can sit outdoors away from direct sunlight. With 71.9% of households owning their home, most can decide without a landlord.
Size it from your own readings
The PVGIS 5.3 model puts a 4 kWp due-south array at the Potters Bar town-centre point at about 141 kWh in December and 479 kWh in June. Your own array will differ with its size, slope and shading, and its generation meter tells you by how much. Bring a year of readings and your electricity bills to the survey, and use our guide to what size home battery you need to think about evening use first. The roof side is on our page on solar panels in Potters Bar, and the rest of the county is on our solar panels in Hertfordshire hub.
Sources: DESNZ, Renewable electricity by local authority, 2014 to 2025 (29 September 2026), Hertsmere; Hertsmere Borough Council, Climate Change and Sustainability Strategy 2025–2030; Energy Networks Association, EREC G98 Issue 2 (10 March 2025) and type-test register; UK Power Networks, Smart Connect and Solar and storage: cost, time and what’s involved; UK Power Networks Open Data licence boundaries; Ofgem, Smart Export Guarantee; Energy Saving Trust, Battery storage (updated 19 August 2026); HMRC VAT Notice 708/6; ONS, Towns and cities: characteristics of built-up areas, Census 2021 (Potters Bar); ONS Census 2021 TS044 by 2022 ward; GOV.UK, Warm Homes: Local Grant successful local authorities (updated 2 July 2026); Switch Together, Hertsmere page (read 15 October 2026); EnSmart published specifications; PVGIS 5.3 (European Commission JRC), PVGIS-SARAH3 2005–2023, run 15 October 2026.