Sources and how the calculators work

Official, reviewed 25 October 2026

• GOV.UK: domestic private rented property, minimum energy efficiency standard, landlord guidance
• GOV.UK: Find an energy certificate

Statistics, reviewed 26 October 2026

• ONS: Energy efficiency of housing in England and Wales, 2025 (median scores; the ONS has said it is discontinuing this series)
• English Housing Survey 2024-25: housing quality and energy efficiency (share of homes by band, cost to reach C)
• English Housing Survey 2022-23: energy report (modelled running costs by band)
• GOV.UK: Find an energy certificate, EPCs when buying, selling or renting and Get a new energy certificate

Official, reviewed 26 October 2026

• GOV.UK: Improving the energy performance of privately rented homes, government response (21 January 2026): the 1 October 2030 deadline, £10,000 cap, exemptions, £30,000 fine and the aim of regulations in force in 2027. Status on our pages: confirmed government policy, not yet law.
• GOV.UK: Boiler Upgrade Scheme, what you can get and eligibility

Analyses of the 2026 announcements (no longer our main source for the 2030 rules)

• Elmhurst Energy: band C by October 2030 (22 January 2026)
• Jones Day: EPC C by 2030 (March 2026)
• Housing Today: EPC reforms moved to the second half of 2027

How the calculators work

• Bands: A 92+, B 81–91, C 69–80, D 55–68, E 39–54, F 21–38, G 1–20.
• Landlord cap: £10,000, or 10% of value under £100,000, minus spending since 1 October 2025.
• Cheapest route: every combination of up to 14 measures is tested; the cheapest that reaches 69 points is shown.
• Payback: (cost − grant) ÷ yearly saving.