16.3kW solar panel, battery and EV charger installation near Llanelli

Cefneithin, LlanelliCardiff showroomInstalled August 2026

The home in Cefneithin, Llanelli, with 34 LONGi panels on the roof and the team finishing up on the scaffold

16.3kWp

solar system size

LONGi 480W panels

27kWh

Tesla battery

11.04kW

built‑in inverter

£2,842

estimated yearly saving

Photos

Tesla Powerwall 3 and Powerwall 3 Expansion fitted inside

The EV charger fitted on the side wall of the house

The story of this install

“Maximise the roof, please”

That was Gwyn's brief when he came to our Cardiff team. His household in Cefneithin, near Llanelli, was spending about £150 a month on electricity, and two electric cars were on the way.

Thirty-four panels on one roof

His big slate roof faces west-south-west at 37°, and there's no shading at all. Ryan from our Cardiff showroom designed it to take 34 LONGi 480W panels, 16.3kWp, which is one of the largest systems we've fitted on a home.

Behind it sits a Tesla Powerwall 3 with a Powerwall 3 Expansion, side by side, for 27kWh of storage.

A west-south-west roof does most of its work from late morning into the evening, which suits a household that charges cars and uses most of its power after work. Anything the house and batteries can't use goes back to the grid and earns Smart Export Guarantee payments.

Ready for two cars and a power cut

Gwyn asked about a Zappi or a Hypervolt for the cars, and went with a black Hypervolt on a 5-metre cable. A Tesla Backup Gateway 2 gives whole-home backup, so if the grid goes down the house stays powered from the batteries.

Living with it

The system was commissioned on 11 August 2026. Over a year, the MCS estimate puts generation at around 13,200kWh, roughly double what the house used before the cars arrived, so there's plenty of room for them.

The system was certified under MCS and approved by the network operator before switch-on. Because the Powerwall 3 has its own built-in inverter, the whole system is managed in one Tesla app, from the panels and batteries to the backup.

Yearly generation is the MCS estimate made for this home before installation, using the standard MCS method. Real output varies from year to year with the weather.

Full kit list

Panels: 34 × LONGi 480W (16.3kWp)
Inverter: Tesla Powerwall 3 (built-in inverter)
Battery: Tesla Powerwall 3 + Powerwall 3 Expansion, 27kWh usable
Backup: Whole-home backup in a power cut (Tesla Backup Gateway 2)
EV charger: Hypervolt home EV charger (black, 5 m cable)
Paperwork: MCS certificates (solar and battery), DNO approval and handover pack