EPC rating and sold prices in NN11 (West Northamptonshire)
In postcode district NN11 (West Northamptonshire), homes rated EPC C or better sold for 2% less per square metre than D–G homes (median £2,666 vs £2,727, 7,495 sales). Like for like — same size, type, build period and year — homes rated C or better sold for 4.0% less (95% range −5.1% to −2.9%). 1 of 5 sectors with enough sales show a difference distinguishable from zero. Data: HM Land Registry to 30 September 2026, EPC register.
From the raw gap to like-for-like
The homes are not alike: C+ homes here have a median floor area of 93 m² against 89 m² for D–G; the most common build period is 2012 onwards for C+ and 1967–1975 for D–G; 68% of C+ and 71% 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 | −0.6% | −2.6% to +1.4% |
| Same floor area | −2.7% | −3.8% to −1.5% |
| + same property type | −0.3% | −1.3% to +0.8% |
| + same build period | −1.1% | −2.5% to +0.2% |
| + same year of sale | −4.0% | −5.1% to −2.9% |
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.
Postcode sectors in NN11
| Sector | Sales | Raw gap | Like-for-like | 95% range |
|---|---|---|---|---|
| NN11 0 | 881 | +5% | +0.8% | −1.1% to +2.7% |
| NN11 2 | 1,209 | −8% | too few | — |
| NN11 3 | 1,307 | −6% | −3.2% | −6.6% to +0.3% |
| NN11 4 | 1,904 | +3% | −2.1% ▼ | −3.6% to −0.5% |
| NN11 6 | 400 | −8% | +1.5% | −4.3% to +7.5% |
| NN11 7 | 267 | −3% | too few | — |
| NN11 8 | 519 | −15% | too few | — |
| NN11 9 | 1,008 | −1% | +0.8% | −1.2% to +2.8% |
▲ green: premium distinguishable from zero; ▼ red: discount; plain: no measurable difference. Small areas have fewer sales, so their 95% ranges are wider.
Sold prices by EPC band in NN11
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 26 | £3,793 |
| B | 1,833 | £2,750 |
| C | 2,117 | £2,560 |
| D | 2,583 | £2,694 |
| E | 683 | £2,857 |
| F | 222 | £2,832 |
| G | 31 | £3,016 |
A median is shown when a band has at least 10 sales.
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.