Sources and review dates
Everything this site states rests on one of the sources below. Each line says what we use it for and when we last read it.
How we use them
Prices come only from DESNZ's battery statistics (published 28 May 2026). Tax, safety, network and funding rules come from the body that sets them. Which? is the only secondary source on price, and it is always marked.
| Source | What we use it for | Last read |
|---|---|---|
| DESNZ: MCS certified domestic battery installation statistics (April 2024 to March 2026 workbook, published 28 May 2026) | Every installed battery price: medians, means, sample sizes and the monthly installation counts. | 3 November 2026 |
| HMRC: VAT on energy-saving materials and heating equipment (Notice 708/6), sections 2.1, 2.3 and 2.19 | The zero rate on installed batteries until 31 March 2027, 5% after, and the standard rate on supply without installation. | 3 November 2026 |
| HMRC: extension of the energy-saving materials relief to electrical batteries (from 1 February 2024) | The date batteries joined the energy-saving materials relief (1 February 2024). | 3 November 2026 |
| BSI / DESNZ: PAS 63100:2024, battery energy storage systems in dwellings (PDF) | Where a home battery can go, what a location needs, and the storage limits per enclosure and per home. | 3 November 2026 |
| IET: Amendment 4 (2026) to BS 7671:2018 published 15 April 2026 | The Wiring Regulations chapter on batteries added by Amendment 4 in April 2026. | 3 November 2026 |
| MCS: notifying distribution network operators (G98 and G99) | G98 notification and G99 application rules for home storage. | 3 November 2026 |
| MCS: find an installer (the public register) | Where to check an installer is certified for battery storage. | 3 November 2026 |
| GOV.UK: Smart Export Guarantee | How the Smart Export Guarantee works for a home with a battery. | 3 November 2026 |
| Ofgem: Smart Export Guarantee (SEG) | That export tariffs must be above zero and are set by each supplier. | 3 November 2026 |
| Ofgem: energy price cap unit rates and standing charges (1 October to 31 December 2026) | The Ofgem price cap unit rate used as a reference import price. | 3 November 2026 |
| Ofgem: review of typical domestic consumption values, decision (May 2026; values from 1 July 2026) | Ofgem's typical annual household use from 1 July 2026. | 3 November 2026 |
| GOV.UK: Warm Homes Loan Scheme factsheet (published 27 October 2026) | The Warm Homes Loan Scheme battery cap and how to apply. | 3 November 2026 |
| GOV.UK: apply for Warm Homes: Local Grant | Warm Homes: Local Grant eligibility in England. | 3 November 2026 |
| DESNZ: Warm Homes Loan Scheme rules, version 3 (September 2026, PDF), sections 2.6 and 4.4 to 4.19 | Who can borrow, the MCS requirements and the typical items in a battery quote. | 3 November 2026 |
| DESNZ: Warm Homes: Local Grant policy guidance (July 2026, PDF), battery rules | When Warm Homes: Local Grant can include a battery (only with solar). | 3 November 2026 |
| Home Energy Scotland: grants and loans | That Home Energy Scotland lists no battery funding. | 2 November 2026 |
| nidirect: support to generate your own electricity (Northern Ireland) | That Northern Ireland names no support for homeowners generating their own electricity. | 20 October 2026 |
| House of Commons Library briefing CBP-9585 on the Warm Homes Plan (PDF) | That the Warm Homes Plan offers no new able-to-pay grant for batteries. | 2 November 2026 |
| National Grid Electricity Distribution: generation and storage connections (G98 and G99) | One network operator's own wording on the G98 route. | 3 November 2026 |
| DESNZ: solar PV cost data (2025/26, published 28 May 2026; excludes batteries) | Why panel prices sit in a separate series that leaves batteries out. | 19 October 2026 |
| Octopus Energy: Outgoing export tariffs (one supplier, an example only) | Dated example export tariffs from one supplier, never quoted as "the rate". | 3 November 2026 |
| HMRC: VAT on fuel and power (Notice 701/19, updated 28 October 2026) | The separate relief on household electricity in Great Britain until 30 June 2027. | 3 November 2026 |
| Easy PV help: limits of the MCS self-consumption lookup method (secondary) | The limits of the MCS self-consumption lookup method (secondary). | 3 November 2026 |
| ASA ruling on British Gas Services Ltd (savings claim, 4 March 2026) | Why we publish no headline savings figures. | 2 November 2026 |
| Which?: solar panel battery storage (secondary source, page updated 30 October 2026) | A secondary range for battery costs, warranty lengths and AC versus DC coupling. | 3 November 2026 |
| European Commission JRC: PVGIS solar yield tool | Annual and seasonal solar yield per kWp in different parts of the UK. | 30 October 2026 |
| Companies House: SEO-DONS LTD (16766013) | The publisher's company record. | 30 October 2026 |
When a source changes, we update the pages that rely on it and their review dates. The DESNZ battery statistics usually update in late May; the Ofgem price cap changes every quarter; the VAT reliefs have fixed end dates we watch. The method that turns the statistics into prices is on the methodology page, and the people responsible are described on about this site. Spotted something out of date? Use the contact page.
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