EPC rating and sold prices in NN15 (North Northamptonshire)
In postcode district NN15 (North Northamptonshire), homes rated EPC C or better sold for 12% more per square metre than D–G homes (median £2,765 vs £2,467, 8,828 sales). Like for like — same size, type, build period and year — homes rated C or better sold for 1.6% more (95% range +0.5% to +2.7%). 1 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 98 m² against 87 m² for D–G; the most common build period is 2012 onwards for C+ and 1950–1966 for D–G; 81% of C+ and 77% of D–G sales are detached or semi-detached houses.
| Comparing C+ with D–G homes… | Difference | 95% range |
|---|---|---|
| Raw gap per m² (medians) | +12% | — |
| Whole price, nothing held equal | +21.3% | +19.4% to +23.2% |
| Same floor area | +12.6% | +11.3% to +13.8% |
| + same property type | +10.5% | +9.5% to +11.6% |
| + same build period | +6.3% | +4.9% to +7.8% |
| + same year of sale | +1.6% | +0.5% to +2.7% |
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 NN15
| Sector | Sales | Raw gap | Like-for-like | 95% range |
|---|---|---|---|---|
| NN15 5 | 3,780 | +7% | +0.8% | −0.8% to +2.3% |
| NN15 6 | 2,956 | +10% | +1.2% | −0.7% to +3.0% |
| NN15 7 | 1,570 | +13% | +4.9% ▲ | +2.0% to +7.8% |
▲ 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 NN15
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 106 | £3,152 |
| B | 3,237 | £2,798 |
| C | 1,812 | £2,651 |
| D | 2,836 | £2,536 |
| E | 704 | £2,233 |
| F | 118 | £2,000 |
| G | 15 | £2,430 |
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.