South Wales (Cardiff, Swansea, Newport) is served by National Grid Electricity Distribution; North and Mid Wales (Wrexham, Bangor, Aberystwyth, Newtown, Llandrindod Wells) by SP Energy Networks' Manweb area. On Octopus rates for 3 November 2026, this site's model puts a 10 kWh battery with 4 kWp of solar on Octopus Flux at about £434 a year in Cardiff and £469 in Wrexham. The Welsh Nest scheme names solar panels but not batteries.
Your electricity region and network operator
Wales spans 2 electricity regions, each with its own prices and network operator:
| Electricity region | Network operator (DNO) | Flat unit rate | Standing charge (pence a day) |
|---|---|---|---|
| South Wales (K) | National Grid Electricity Distribution (South Wales) | 26.55p/kWh | 54.44 |
| Merseyside and North Wales (D) | SP Energy Networks (SP Manweb) | 27.86p/kWh | 67.27 |
What a battery can buy low and use high
The rates that decide a battery's saving in Wales:
| Rate | South Wales | Merseyside and North Wales |
|---|---|---|
| Octopus Flux import, 2am to 5am | 16.14p | 16.94p |
| Octopus Flux import, 4pm to 7pm | 37.33p | 39.16p |
| Octopus Flux export, 4pm to 7pm | 30.26p | 31.75p |
| Octopus Go overnight import | 9.40p | 9.40p |
| Octopus Go daytime import | 34.51p | 35.75p |
| Outgoing Octopus flat export | 12.00p | 12.00p |
| Agile Octopus, average of each day's cheapest 3 hours | 19.90p | 19.90p |
| Agile Octopus, average 4pm to 7pm | 51.53p | 52.53p |
| Flux spread: peak import minus off-peak | 21.19p | 22.22p |
Solar yield across Wales
Modelled output of a 4 kWp south-facing array:
| Place | kWh a year | June | December | Electricity region |
|---|---|---|---|---|
| Cardiff | 4,167 | 524 | 129 | South Wales |
| Swansea | 4,056 | 510 | 129 | South Wales |
| Newport | 4,129 | 516 | 129 | South Wales |
| Wrexham | 3,870 | 477 | 122 | Merseyside and North Wales |
| Bangor | 3,244 | 443 | 67 | Merseyside and North Wales |
| Aberystwyth | 3,816 | 479 | 108 | Merseyside and North Wales |
How often the power goes off
Ofgem's reliability figures for the networks serving Wales (lower is better):
| Network area | Interruptions per 100 customers | Minutes lost per customer | Against the GB average |
|---|---|---|---|
| Southern Wales | 42.1 | 27.51 | Fewer minutes lost |
| Cheshire, Merseyside and Northern Wales | 28.55 | 34.54 | Close to average |
Solar already on Wales's roofs: DESNZ counts 124,516 domestic-scale solar installations in Wales (496 MW) at the end of Jul 2026.
A home in Cardiff using 3,000 kWh a year, with 4 kWp of solar, adds a 10 kWh battery. Yearly savings with Cardiff's solar yield and South Wales rates, against no battery on a flat tariff:
| Tariff with the battery | Modelled saving a year | Energy charged from the grid |
|---|---|---|
| Octopus Flux, selling spare stored energy at the peak | £434 | 1,216 kWh |
| Staying on a flat tariff (solar storage only) | £169 | 0 kWh |
| Same home with no solar, battery on Agile Octopus | £128 | 3,258 kWh |
| Same home with no solar and an electric car, battery on Octopus Go | £467 | 3,258 kWh |
Flux needs solar panels and Go is for electric car owners. How the model works · try your own numbers.
South Wales and North Wales are priced differently
| South Wales (NGED) | North and Mid Wales (SP Manweb) | |
|---|---|---|
| Towns confirmed by postcode | Cardiff, Swansea, Newport | Wrexham, Bangor, Aberystwyth, Newtown, Llandrindod Wells |
| Flexible Octopus standing charge (3 Nov 2026) | 54.44p a day | 67.27p a day, the highest in Britain |
| Octopus Flux, 2am to 5am / 4pm to 7pm (3 Nov 2026) | 16.14p / 37.33p | 16.94p / 39.16p |
| Flux spread | 21.19p | 22.22p, the widest in Britain |
| Modelled saving, 10 kWh with 4 kWp solar on Flux | £434 a year (Cardiff) | £469 a year (Wrexham) |
| Ofgem 2024/25 interruptions per 100 customers | 42.10 | 28.55 |
| Minutes lost per customer | 27.51 | 34.54 |
The Manweb side of Wales pays the most for electricity in Britain, which makes each kWh a battery shifts worth more there. These are the rates Octopus published for 3 November 2026, after its 19 October Flux rise; the page carried 26 September rates before. South Wales sees more interruptions but fewer minutes lost per customer.
Solar from Cardiff to Bangor
PVGIS models a 4 kWp south-facing array at 4,167 kWh a year in Cardiff, 4,129 in Newport and 4,056 in Swansea, which puts the south coast of Wales ahead of the English Midlands. Further north it varies sharply: 3,870 in Wrexham and 3,816 in Aberystwyth, but only 3,244 in Bangor, where PVGIS’s horizon data (the high ground to the south) cuts winter sun and December output falls to about 67 kWh, among the lowest of any town in this guide. In north-west Wales especially, a battery’s winter value comes almost entirely from cheap-rate charging. DESNZ counts 124,516 domestic-scale solar installations in Wales.
Funding in Wales
- Nest Warm Homes Programme: free home-energy improvements for owner-occupiers and private renters on means-tested benefits or a low income, in a home rated EPC 54 (band E) or below, or 68 (band D) or below where someone has an eligible health condition. The Welsh Government lists boiler repairs or replacement, heat pumps, insulation and solar panels. Batteries are not listed.
- ECO4: a battery can be installed during an ECO4 retrofit but earns no ECO score, and ECO4 ends on 31 December 2026.
- UK-wide help: 0% VAT on installed batteries until 31 March 2027. The Warm Homes Loan Scheme also covers Welsh homes: its rules make any domestic property in the United Kingdom eligible, and a scheme lender can lend up to £15,000 for a battery, after its own credit checks.
Rules that differ in Wales
The Building Regulations apply in their Welsh form. Rather than England’s list of notifiable electrical work, in Wales work is exempt from notification only if Schedule 4 lists it, so a battery installation should be done by an installer registered with a competent person scheme who can self-certify it, or notified to building control. The fire-safety rules on where a battery can go (PAS 63100) and the network rules (G98 and G99) are the same as in England.
Getting quotes
Give installers your full postcode so they use the right network’s rates and process. SP Energy Networks gives installers 30 days after commissioning to notify it of a small system; National Grid in the south uses 28. Compare home battery storage quotes on usable kWh and price per kWh, and check the installer on the MCS register for battery storage.
Adding a battery to solar in Cardiff, Swansea and Newport
Many of the Cardiff searches that reach this site ask about “retro fit” battery storage, meaning a battery for a home that already has panels, which is the simplest kind of job. A battery added to existing solar is normally AC-coupled: it has its own inverter and connects to the home’s supply next to the solar inverter, so the roof is untouched. The alternative, replacing the solar inverter with a hybrid one so the panels charge the battery directly, only makes sense when the old inverter is near the end of its life. The retrofit guide covers both, and AC against DC coupling sets out the trade-off.
South Wales is a good place to do it. PVGIS models a 4 kWp south-facing array at 4,167 kWh a year in Cardiff, with 524 kWh in June and 129 kWh in December: roughly four times as much in midsummer as in midwinter. A battery fills from the panels from spring to autumn, so most of its saving comes from using that solar after dark. In winter, when Cardiff’s panels give so little, the battery’s job changes: it charges on a cheap overnight rate and covers the evening peak. Which tariff you choose decides the saving more than the battery brand, so run your own figures in the savings calculator before you accept a quote.
What the network needs
Your installer deals with National Grid Electricity Distribution, not you. The test is the combined rating of every inverter that can export, the solar inverter plus the battery inverter. At or below 16 A per phase (3.68 kW on a single-phase supply) the installer notifies the network within 28 days of commissioning under G98. Above that, a G99 application goes in before installation and can come back with an export limit; the G99 guide explains the fast-track categories. A 4 kWp array with a 5 kW battery inverter adds up to more than 3.68 kW, so ask your installer which route yours needs before you sign.
What it costs
There is no separate Welsh price list: quotes in Cardiff, Swansea and Newport follow the published UK figures. Octopus’s published battery-only installations start at £3,947 for about 5 kWh and £5,336 for about 10 kWh, and Heatable’s median quote for a battery added to existing solar is £6,500. Installed batteries carry 0% VAT until 31 March 2027, so query any quote that adds VAT to an installed battery. The detail by size is on the cost page.
Choosing and checking an installer
- Ask for the postcode check. A South Wales installer should name National Grid Electricity Distribution; one covering Wrexham or Bangor should name SP Energy Networks.
- Ask who self-certifies. In Wales the Building Regulations list what is exempt from notification, so you want a competent person scheme member who can sign the job off.
- Ask for the MCS number. It is needed for Octopus Flux and the Smart Export Guarantee, and the MCS register shows who is certified for battery storage.
- Ask where the battery goes. The fire-safety guidance in PAS 63100 restricts some locations, and an installer who has not heard of it is a warning.
- Compare on usable kWh. Divide each total price by usable capacity, not the headline figure on the datasheet.
Put your full postcode in the form on this page and we reply by email, using the figures you entered and the right network and tariff for your postcode. This site does not install batteries.
Home batteries in Wales: questions
Is there a grant for home batteries in Wales?
Not a dedicated one. The Welsh Government's Nest Warm Homes Programme provides free measures for eligible low-income households and names boilers, heat pumps, insulation and solar panels, but not batteries. Installed batteries carry 0% VAT until 31 March 2027, and the UK-wide Warm Homes Loan Scheme offers loans of up to £15,000 for a battery.
Which network operator covers North Wales?
SP Energy Networks, through its Manweb licence area, which also covers Merseyside and Cheshire. Wrexham, Bangor, Aberystwyth, Newtown and Llandrindod Wells were confirmed by postcode. South Wales, including Cardiff, Swansea and Newport, is National Grid Electricity Distribution's South Wales area.
Do building regulations for a battery differ in Wales?
Wales has its own version of the Building Regulations. In Wales, electrical work is exempt from notification only if it is listed in Schedule 4, rather than following England's list of notifiable work, so use an installer registered with a competent person scheme who can self-certify the work.
Can I add a battery to my existing solar panels in Cardiff?
Yes. Most retrofits are AC-coupled: the battery has its own inverter and connects beside the panels' inverter, so nothing on the roof changes. Cardiff is on National Grid Electricity Distribution's South Wales network, and your installer notifies it within 28 days of commissioning if the combined inverters are within 3.68 kW on a single-phase supply, or applies in advance under G99 if they are above it.
How much does a battery cost to install in South Wales?
There is no separate Welsh price list: quotes for Cardiff, Swansea and Newport follow the UK range. Octopus lists battery-only installations from £3,947 for about 5 kWh and £5,336 for about 10 kWh, and Heatable's median quote for a battery added to existing solar is £6,500. Installed batteries carry 0% VAT until 31 March 2027. Get at least three written quotes and compare them on usable kWh and price per kWh.
Do I need a different installer in Wales?
You need an installer who covers your postcode, is registered with a competent person scheme so the work can be self-certified under the Welsh Building Regulations, and is on the MCS register for battery storage if you want Octopus Flux or the Smart Export Guarantee. Ask which network operator they will notify: it is National Grid Electricity Distribution in the south and SP Energy Networks in the north.