Lewes cellars, listed interiors and the retrofit question

Lewes is twenty-three road miles east along the A27 and, in the National Park Authority’s own words, the largest town in the South Downs National Park and any National Park, lying on the Ouse where it cuts through the chalk of the Downs. Almost all the historic town is a conservation area — designated in 1970, extended by the Authority in 2012 — with an Article 4 Direction over it. And a lot of its roofs already have panels: Solar Together Sussex reported over 1,600 homes fitted by its third phase in 2023 and offered retrofit battery storage to households that already had them. So a Lewes battery survey has an order, and here it is.

1. The inverter that is already there

The survey starts at the wall where the existing inverter sits: its make and age, its paperwork, what the array actually produces. Some inverters can take a battery directly. Others mean a battery inverter alongside — an AC-coupled battery, which is a cleaner job than it sounds. A system that was notified to the operator properly when it went in makes the next step easier; one that was not gets tidied up as part of the job.

2. The board

On a house whose panels went in some years ago the consumer unit is sometimes the real work. We look at it before we look at where the stack goes, because a board with nowhere left to go changes the quote more than the battery does.

3. The cellar, and the listed question

PAS 63100:2024 — the fire-safety specification home batteries have been installed to since April 2026 — wants the stack out of the living space and away from escape routes, with clearances and detection around it. In a flint-and-tile Lewes town house that is usually a dry cellar or a utility, and the position is agreed in a minute. Where the house is listed there is a second question: the position of the stack and the route of the cables can need consent even though the outside is untouched, so a drawing goes to the National Park Authority’s conservation officer before we quote. The Park itself does not reach a battery indoors; it is an electrical installation.

4. The size, and the yardstick

The battery is sized to the evening load from half-hourly data or bills, and with the best modelled yield of the three regions we publish — about 1,177 kWh per kWp a year for a south-facing array — the surplus a Lewes battery can keep is larger than most. We hold our own quote against the Solar Together prices, which remain a fair yardstick for anyone’s, and if the arithmetic does not support a battery, the quote says so.

5. The paperwork

BN7 and BN8 are UK Power Networks, group J on the 18 October 2026 lookup. The new inverter is notified under G98 if it is up to 16 amps per phase, or applied for under G99 before it is energised if it is larger — and adding a battery inverter to an existing array is one of the commoner ways a house crosses that line. The handover pack covers both halves of the system. In a district where private renting has risen to 16.9% of households, the first question in a good many houses is the landlord’s; we will talk to either side.

Where to go next

Battery storage in Lewes is the page for the job and solar panels in Lewes is the roof side. Adding a battery to panels you already have in East Sussex is the retrofit in detail across the coast; PAS 63100: where a home battery can go is the specification; G98 or G99 explained is the paperwork. West along the coast, Brighton’s post is the converted-house question. The county picture is on the battery storage page.