EPC rating and sold prices in NN17 (North Northamptonshire)
In postcode district NN17 (North Northamptonshire), homes rated EPC C or better sold for 16% more per square metre than D–G homes (median £2,530 vs £2,179, 6,702 sales). Like for like — same size, type, build period and year — homes rated C or better sold for 1.7% more (95% range +0.2% to +3.1%). 2 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 90 m² against 82 m² for D–G; the most common build period is 2012 onwards for C+ and 1950–1966 for D–G; 71% of C+ and 64% of D–G sales are detached or semi-detached houses.
| Comparing C+ with D–G homes… | Difference | 95% range |
|---|---|---|
| Raw gap per m² (medians) | +16% | — |
| Whole price, nothing held equal | +28.2% | +25.7% to +30.8% |
| Same floor area | +16.2% | +14.5% to +17.9% |
| + same property type | +13.7% | +12.2% to +15.3% |
| + same build period | +9.1% | +7.0% to +11.2% |
| + same year of sale | +1.7% | +0.2% to +3.1% |
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 NN17
| Sector | Sales | Raw gap | Like-for-like | 95% range |
|---|---|---|---|---|
| NN17 1 | 1,309 | +10% | +3.1% ▲ | +0.6% to +5.6% |
| NN17 2 | 1,670 | +7% | +3.2% ▲ | +1.5% to +4.9% |
| NN17 3 | 1,584 | 0% | +0.8% | −2.8% to +4.4% |
▲ 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 NN17
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 154 | £2,660 |
| B | 2,937 | £2,577 |
| C | 1,216 | £2,342 |
| D | 1,834 | £2,215 |
| E | 468 | £2,017 |
| F | 77 | £2,455 |
| G | 16 | £2,025 |
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.