Open book

Sources and dates

Every figure on this site comes from a published source. We check them regularly and show the date. Prices and rates change, so treat all figures as estimates.

GOV.UK, VAT Notice 708/6: energy-saving materials. Zero rate 1 May 2023 to 31 March 2027, then 5%. A standalone battery and a battery retrofitted to solar are covered from 1 February 2024. Source (Read 7 October 2026)
HMRC, Revenue and Customs Brief 10 (2026): temporary zero rate of VAT for domestic electricity in Great Britain, 1 October 2026 to 31 March 2027. Source (Published 8 September 2026)
Ofgem, changes to the price cap 1 October to 31 December 2026: electricity 26.32p per kWh and 54.83p a day standing charge (Great Britain average, standard variable tariff, direct debit). Source (Published 26 August 2026)
Ofgem, Smart Export Guarantee: SEG tariff rates must always be above zero. Source (Read 7 October 2026)
Octopus Energy, Smart Export Guarantee: a flat 4.1p per kWh for every unit exported, open to customers of any import supplier. Outgoing Octopus 12p per kWh. Source (Read 7 October 2026)
British Gas, Export Premium 12p per kWh for its electricity customers (systems up to 15kW); Export SEG 3p per kWh for others. Source (Page updated 27 August 2026)
E.ON Next, Export Premium v3: 17.5p per kWh fixed for 12 months, for solar or battery installed by E.ON Installation Services from 10 November 2025. Source (Read 7 October 2026)
EDF, Export Exclusive 12m V3: 18p per kWh, for solar, a battery or both bought from EDF after 2 March 2026. Source (Read 7 October 2026)
Energy Saving Trust, solar panels: about £7,600 for a typical 4.5 kWp system; payback of 9 to 12 years across four cities on July 2026 fuel prices; typically about 12p per unit exported; panels last 25 years or more. Source (Updated 1 October 2026)
Energy Saving Trust, battery storage: £1,500 to £10,000, about £4,600 for 5 kWh; typical life 10 to 12 years. Source (Updated 6 October 2026)
Energy Saving Trust, plug-in solar: legal in Great Britain from 27 August 2026; from around £450; about £70 to £100 a year; 800W; one device per home; register before use; landlord or freeholder permission. Source (Updated 1 October 2026)
GOV.UK, households can save as plug-in solar panels come to market: up to 800W, up to £110 a year, permissions to check before installing. Source (Published 26 August 2026)
Planning Portal, solar equipment mounted on a house or a block of flats: 200mm projection, not above the highest part of the roof, conservation area and listed building limits, plug-in solar not on timber-clad surfaces. Source (Read 7 October 2026)
MCS, record number of UK households combining renewables: 210,000 installations in the first half of 2026, 36,000 batteries, 92% of battery installs onto homes with solar. Source (Read 7 October 2026 (page undated))
GOV.UK, Warm Homes Plan announcement: government-backed zero and low interest loans for solar panels, batteries and heat pumps. Source (Published 20 January 2026)
GOV.UK, Warm Homes Loan Scheme lender applications (first stage closed, further window expected later in 2026). Source (Updated 17 September 2026)
Octopus Energy public tariff data for the South East (region J), read from the public tariff interface: Intelligent Octopus Go 12-month fixed 7.6p night rate; Octopus Go 12-month fixed 9.5p; Octopus Go variable about 8.2p cheap window; Cosy about 12.6p cheap rate. Source (Read 7 October 2026)
GOV.UK, Boiler Upgrade Scheme grant raised from £7,500 to £9,000 for oil and LPG homes from 21 July 2026. Source (Published 26 June 2026)
GOV.UK, EV chargepoint grant for flat owners and renters: up to £500, available until 31 March 2027. Source (Updated 1 April 2026)
National Grid, G98 connection procedures: micro-generation up to 16A per phase, installation document within 28 days of commissioning. Source (Read 7 October 2026)
legislation.gov.uk, Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 14. Source (Read 7 October 2026)
ONS Census 2021 via Nomis, accommodation type for the Swale local authority: 60,495 households; 33.7% semi-detached, 29.8% terraced, 23.9% detached, 8.6% purpose-built flats. Source (Census 2021)
ONS, Census 2021 area changes for Swale: 67.0% owned, 18.4% private rented, 13.3% social rented. Source (Census 2021)
Planning data platform, conservation area records supplied by Swale Borough Council (52 records, including Faversham Town, Faversham - Ospringe, Faversham - Preston-next-Faversham, three at Boughton, two at Selling and two at Graveney). Source (Read 7 October 2026)
Planning data platform, Kent Downs boundary: our own point check found Sheldwich and Throwley inside it and Faversham town centre outside it. Boundaries cross parishes, so check your address. Source (Checked 7 October 2026)
Wikipedia, Faversham: creek, market, parish church, Davington Priory, Southeastern rail links. Source (Read 7 October 2026)
Wikipedia, ME postcode area, with the village pages for Oare, Teynham, Sheldwich, Selling and Throwley. Source (Read 7 October 2026)
European Commission, clean energy islands: guidance on salt exposure for solar PV in coastal areas (IEC 61701 salt mist; corrosion-resistant mounting). Source (Published 1 July 2026)
UK Power Networks, annual review: its South Eastern Power Networks area serves South London, Kent, East Sussex and parts of Surrey and West Sussex. Source (Read 7 October 2026)

What is our own estimate

The cost ranges and savings on our cost pages are our own estimates, built on the sources above. They assume a typical roof making about 900 kWh for each kWp a year, 35% of solar power used in the house, a battery that loses about 10% of power, and a house using 3,000 kWh a year. They are not quotes. Last reviewed 7 October 2026.