EPC rating and sold prices in NN4 (West Northamptonshire)
In postcode district NN4 (West Northamptonshire), homes rated EPC C or better sold for 1% more per square metre than D–G homes (median £3,033 vs £2,993, 9,440 sales). Like for like — same size, type, build period and year — the difference is +0.6% (95% range −0.2% to +1.5%): the EPC band itself is not reflected in sale prices here. 3 of 6 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 91 m² against 87 m² for D–G; the most common build period is 2012 onwards for C+ and 1983–1990 for D–G; 65% of C+ and 74% of D–G sales are detached or semi-detached houses.
| Comparing C+ with D–G homes… | Difference | 95% range |
|---|---|---|
| Raw gap per m² (medians) | +1% | — |
| Whole price, nothing held equal | +4.1% | +2.3% to +5.9% |
| Same floor area | +2.0% | +0.9% to +3.1% |
| + same property type | +7.7% | +6.8% to +8.7% |
| + same build period | +5.4% | +4.4% to +6.5% |
| + same year of sale | +0.6% | −0.2% to +1.5% |
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 NN4
| Sector | Sales | Raw gap | Like-for-like | 95% range |
|---|---|---|---|---|
| NN4 0 | 2,228 | +7% | 0.0% | −1.3% to +1.2% |
| NN4 5 | 929 | −8% | −2.8% ▼ | −5.1% to −0.4% |
| NN4 6 | 2,092 | +2% | +0.9% | −0.8% to +2.6% |
| NN4 7 | 151 | +4% | +9.0% ▲ | +2.0% to +16.4% |
| NN4 8 | 2,330 | +9% | +2.7% ▲ | +1.0% to +4.4% |
| NN4 9 | 1,710 | −10% | −1.5% | −3.5% to +0.6% |
▲ 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 NN4
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 64 | £3,779 |
| B | 1,749 | £3,000 |
| C | 3,411 | £3,030 |
| D | 3,583 | £3,040 |
| E | 558 | £2,690 |
| F | 63 | £2,232 |
| G | 12 | £1,750 |
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.