Revealed: England and Wales' most and least energy-efficient areas

How energy efficient are homes where you live?

Across England and Wales, 38.1% of existing homes reach EPC band A to C and 5.0% sit in the worst bands, F or G (DESNZ EPC data, 2026). The postcode gap is stark: measured across all certificates lodged since 2008, the F or G share runs from 22.3% in Gwynedd to 1.0% in Harlow and Stevenage. Recent certificates read lower everywhere, but the rural gap persists.

Last updated: July 2026. Below we set out the worst and best local authorities, the regional picture, a second heating-cost measure from the same dataset, and our full method, all drawn from the DESNZ EPC open dataset.

Key findings

The headline numbers, each summed directly from the source cells.

• Just 38.1% of existing homes in England and Wales reach EPC band A to C, and 5.0% sit in the worst bands, F or G (DESNZ EPC data, 2026).
• The postcode gap is 22-fold across all certificates since 2008: 22.3% F/G in Gwynedd against 1.0% in Harlow and Stevenage. On recent certificates the gap narrows sharply, with Gwynedd's F/G share down to 9.6%, but the rural disadvantage persists (DESNZ EPC data, 2026).
• The least efficient areas are rural, off-gas-grid Wales and the South West: Gwynedd, Ceredigion, Eden, Powys and Cornwall (DESNZ EPC data, 2026).
• Cornwall has the worst F/G rate of any of the country's largest authorities, at 16.7% of its 266,329 certificates (DESNZ EPC data, 2026).
• Tower Hamlets leads the country, with 66.8% of existing homes rated A to C and the lowest modelled heating cost, about £470 a year (DESNZ EPC data, 2026).
• By region, the South West's 7.7% F/G share is about 2.5 times London's 3.1% (DESNZ EPC data, 2026).

How we compiled this data

We used the DESNZ Energy Performance of Buildings Certificates statistics, live data tables EB1 and EB3 (existing domestic properties) and D1 (all properties), covering every certificate lodged on the England and Wales register from Quarter 4 2008 to 31 March 2026, published on 19 May 2026. Band shares use EB1, existing homes only, which removes the new-build skew. For each of 344 local authorities with at least 10,000 lodgements we summed every quarter and calculated the F plus G share and the A to C share across 24,526,026 certificates. Heating cost uses EB3 over the latest four quarters only, so a single consistent modelled fuel-price basis applies.

We rank the least efficient areas on the F or G share, the clearest lens on the worst-performing stock. This is not cherry-picking: the same rural, off-gas-grid authorities that top the F or G table also sit well below the England and Wales average on the positive A to C measure, so the ranking holds whichever end of the scale you read.

Three caveats matter. EPCs count certificates, not unique dwellings, so a home reassessed on multiple sales is counted more than once; band shares are robust to this, but absolute figures are certificates rather than homes. The register is a large, consistent sample of transacting and retrofitted stock, not a full census. Heating cost is DESNZ's RdSAP modelled figure at standard occupancy, not measured bills, so use it for comparing areas rather than as an actual bill.

The Isles of Scilly is often reported as England and Wales' least efficient area, but its very small certificate count makes it a statistical outlier, so we excluded any authority under 10,000 lodgements. For transparency, we held out five low-sample or allocation-affected authorities (Isles of Scilly, Barnsley, Sheffield, City of London and an Unknown bucket). The 19 May 2026 release corrected most local-authority allocation errors in the source tables.

The 15 least efficient local authorities (existing homes)

Which areas have the least energy-efficient homes?

The least efficient homes cluster in rural Wales and the South West, almost all off the mains gas grid. The worst authorities are led by Gwynedd (22.3% of existing homes in bands F or G), Ceredigion (20.6%) and Eden (20.2%), followed by Ryedale, Isle of Anglesey, West Devon and Powys (DESNZ EPC data, 2026). These are areas of older, solid-wall stock heated by oil, LPG or electricity rather than mains gas.

Cornwall is the largest poorly served area. Of its 266,329 existing-home certificates, 16.7% fall in bands F or G, the worst rate of any of the country's largest authorities, those with 250,000 or more certificates (DESNZ EPC data, 2026).

At the other end, new towns and dense London boroughs heat most efficiently. Harlow and Stevenage record just 1.0% of homes in bands F or G, with Tower Hamlets at 1.3% and Crawley at 1.5%, reflecting post-war planned stock and flats. Tower Hamlets also leads the country on the positive measure, with 66.8% of existing homes rated A to C.

By region, the South West has the highest share of worst-band homes at 7.7%, against just 3.1% in London, so a South West home is about 2.5 times more likely to sit in the lowest efficiency bands.

The gap is closing but not closed. Over the most recent two years, Gwynedd's F/G share fell to 9.6%, well below its all-time 22.3% average, yet it remains the worst authority in the country: newer certificates are more efficient everywhere, but the rural, off-gas-grid disadvantage persists.

Headline figures can flatter the picture. Counting all homes including new build lifts the A to C share from 38.1% to 44.6%, so the existing stock, where boiler and heating upgrades actually matter, is materially worse than all-property numbers suggest (DESNZ EPC data, 2026).

A second measure, heating cost, tells the same story

A second measure from the same dataset, DESNZ's modelled annual heating cost per dwelling, points to the same map. Heating a home is modelled at £1,443 a year in Cotswold, £1,393 in Powys and £1,354 in Ceredigion, against an England and Wales average of £897 and a low of £470 in Tower Hamlets. That is a 3.1-fold gap, driven by home age, size, fuel and insulation (DESNZ EPC EB3, 2026). The eight cheapest-to-heat authorities are all London boroughs. Both measures come from the same EPC certificates, so they are not independent proofs, but the low-band league and the heating-cost league top out in the same rural, off-gas-grid areas, which is what you would expect.

Highest and lowest modelled heating cost per home

Cite or reuse this data

This analysis is compiled entirely from public government data, and you are free to cite it. Please attribute to Smart Plan and link back, for example: "Analysis of DESNZ Energy Performance of Buildings Certificates statistics (tables EB1 and EB3, England and Wales, 2008 to 31 March 2026, revised 19 May 2026) by Smart Plan."

Before publishing, check the original DESNZ tables and the DESNZ statistics release calendar for the latest release. Last updated: July 2026.

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Boiler efficiency by area: FAQs

Related pages and sources

• UK boiler repair & cover costs: 2026 statistics
• Thinking about a new boiler?
• Boiler Upgrade Scheme grants
• Boiler & central heating cover
• DESNZ: Energy Performance of Buildings Certificates statistics
• DESNZ: live tables on Energy Performance of Buildings Certificates