EPC rating and sold prices in NN12 (West Northamptonshire)
In postcode district NN12 (West Northamptonshire), homes rated EPC C or better sold for 9% more per square metre than D–G homes (median £3,630 vs £3,315, 5,905 sales). Like for like — same size, type, build period and year — homes rated C or better sold for 1.8% less (95% range −3.3% to −0.3%). 0 of 3 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 97 m² against 97 m² for D–G; the most common build period is 2012 onwards for C+ and before 1900 for D–G; 74% of C+ and 78% of D–G sales are detached or semi-detached houses.
| Comparing C+ with D–G homes… | Difference | 95% range |
|---|---|---|
| Raw gap per m² (medians) | +9% | — |
| Whole price, nothing held equal | +3.7% | +1.4% to +6.1% |
| Same floor area | +7.4% | +6.1% to +8.7% |
| + same property type | +7.8% | +6.6% to +8.9% |
| + same build period | +1.5% | −0.3% to +3.2% |
| + same year of sale | −1.8% | −3.3% to −0.3% |
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 NN12
| Sector | Sales | Raw gap | Like-for-like | 95% range |
|---|---|---|---|---|
| NN12 6 | 3,329 | +15% | −0.7% | −2.7% to +1.4% |
| NN12 7 | 1,014 | +1% | −2.2% | −4.8% to +0.5% |
| NN12 8 | 1,562 | +1% | −1.4% | −4.7% to +1.9% |
▲ 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 NN12
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 45 | £4,047 |
| B | 2,332 | £3,727 |
| C | 1,186 | £3,378 |
| D | 1,566 | £3,359 |
| E | 539 | £3,254 |
| F | 200 | £3,117 |
| G | 37 | £3,125 |
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.