Does a C-or-better EPC sell for more in TW17 9 (Spelthorne)?
A small premium for a better EPC here. In postcode sector TW17 9 (Spelthorne), comparing like with like — same floor area, property type, build period and year of sale — homes rated C or better sold for 5.2% more (95% range +1.1% to +9.4%). The raw gap is different: C+ homes sold for 2% less per square metre than D–G homes (median £5,293 vs £5,389, 505 sales 2015–2026), mostly because they are different homes. Across England and Wales the like-for-like figure is +1.2%. Data: HM Land Registry Price Paid to 30 September 2026 matched to the EPC register.
From the raw gap to like-for-like
The homes are not alike: C+ homes here have a median floor area of 98 m² against 97 m² for D–G; the most common build period is 2012 onwards for C+ and 1950–1966 for D–G; 41% of C+ and 67% of D–G sales are detached or semi-detached houses.
| Comparing C+ with D–G homes… | Difference | 95% range |
|---|---|---|
| Raw gap per m² (medians) | −2% | — |
| Whole price, nothing held equal | +1.9% | −6.6% to +11.3% |
| Same floor area | −0.9% | −4.8% to +3.2% |
| + same property type | +8.8% | +5.0% to +12.8% |
| + same build period | +6.3% | +2.3% to +10.5% |
| + same year of sale | +5.2% | +1.1% to +9.4% |
The first row compares median prices per m²; the second compares whole prices; each later row adds one more thing that must be equal, ending with the like-for-like premium (regression of log price; build period from the certificate, 12 bands). The raw gap per m² and the whole-price gap differ because C+ and D–G homes differ in size.
Sold prices by EPC band in TW17 9
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 3 | too few |
| B | 61 | £5,517 |
| C | 120 | £5,143 |
| D | 187 | £5,377 |
| E | 86 | £5,259 |
| F | 37 | £5,559 |
| G | 11 | £5,694 |
A median is shown when a band has at least 10 sales.
C or better vs D–G, by property type
| Type | C+ sales | C+ £/m² | D–G sales | D–G £/m² |
|---|---|---|---|---|
| Detached | 59 | £5,648 | 152 | £5,905 |
| Semi-detached | 17 | £5,516 | 64 | £5,613 |
| Terraced | 44 | £5,300 | 38 | £5,128 |
| Flat / maisonette | 64 | £5,082 | 67 | £4,508 |
Compared with the wider area
| Area | Sales | Like-for-like | 95% range |
|---|---|---|---|
| Sector TW17 9 | 505 | +5.2% | +1.1% to +9.4% |
| District TW17 | 2,343 | +3.2% | +1.3% to +5.1% |
| England and Wales | 1,000,000 (sample) | +1.2% | +0.9% to +1.5% |
Average gas use in TW17 9 (2024): meters vs certificates
A rough comparison: the certificate figure is an upper-bound estimate (primary energy including lighting, converted with one factor), so treat the share as an order of magnitude.
| Postcodes with published gas data (5+ meters) | 67 (1,172 meters) |
|---|---|
| Median gas use per meter (median of postcodes) | 13,130 kWh |
| Gas-heated homes with an EPC | 791 |
| Energy implied by their certificates (median) | 19,235 kWh |
| Metered gas as a share of the certificate figure (median of 65 postcodes) | 65% (middle half 60%–79%) |
Certificates by band imply: B 7,271 kWh (65 homes) · C 12,908 kWh (240 homes) · D 20,772 kWh (338 homes) · E 31,146 kWh (120 homes) · F 51,499 kWh (23 homes). Across England and Wales, real use is much closer to the certificate for A–C homes than for D–G homes, so the saving an upgrade promises is usually smaller than the certificate suggests.
Certificate energy = primary energy per m² × floor area ÷ 1.13, for homes whose latest certificate shows mains gas heating; it also covers lighting and other uses, so it is an upper bound for gas. DESNZ gas is weather-corrected and covers all meters in the postcode, with or without a certificate.
Can the local grid take heat pumps in TW17 9?
About 680 of the 707 gas-heated homes with an energy certificate in TW17 9 (96%) could switch to a heat pump before their local substations run out of spare capacity, on UK Power Networks' figures. 1 of the 22 local substations would fill up before every gas-heated home they supply could switch.
| Local (street) substations serving homes in the sector | 22 |
|---|---|
| Already at or over capacity | 0 (0%) |
| Their combined spare capacity (demand headroom) | ≈ 4,980 kVA |
| Heat pumps that spare capacity could take, at 1.7 kW each | ≈ 2,930 |
| Gas-heated homes with an EPC on these substations | 707 (89% of the sector's) |
| Of them, could switch within the spare capacity | ≈ 680 (96%) |
| …if each heat pump adds 3 kW (a cold snap) | ≈ 600 (85%) |
How: each substation's spare capacity (UK Power Networks publishes utilisation in 20% bands; we take the low end of the spare-capacity band) is divided by 1.7 kW, the extra winter peak one heat pump adds once many are spread over a street; a substation can take as many heat pumps as that allows, shared among the gas-heated homes on all its postcodes whose centre lies inside the substation's published supply area. Some substations also serve neighbouring sectors, so their whole capacity is counted here and there. Spare capacity is UK Power Networks' figure as published on 15 June 2026; network operators must still be told about each heat pump, and a full substation means reinforcement (usually a delay), not a refusal. Homes without an energy certificate are not counted. All areas and the method.
505 of 610 house and flat sales in the sector since 2015 (83%) were matched to a certificate.
How this is calculated
- Every standard sale (HM Land Registry Price Paid, category A) since January 2015 is matched to the latest energy certificate of the same address (postcode + house number or name + flat) lodged from 10 years before to 3 months after the sale; sales with no certificate or an ambiguous match are left out. Across England and Wales 92% of sales match.
- Price per m² uses the certificate's total floor area (15–1,000 m²).
- Like-for-like premium: regression of the log of price on “C or better”, log floor area, property type, the certificate's build period and the year of sale. The 95% range shows how precise the estimate is; when it includes zero, the data cannot tell the premium apart from none.
Caveats
- The band is the one on the certificate before the sale; certificates are a median 0.8 years old at the sale, but a quarter are over 4 years old and some homes were improved since.
- Condition, garden, parking, views and the exact position within the sector are not known; a premium could hide in them, or they could hide one.
- Individual sales and addresses are not shown.