EPC rating and sold prices in AL9 (Welwyn Hatfield)
In postcode district AL9 (Welwyn Hatfield), homes rated EPC C or better sold for 9% less per square metre than D–G homes (median £4,746 vs £5,215, 1,618 sales). Like for like — same size, type, build period and year — homes rated C or better sold for 3.4% more (95% range +0.6% to +6.2%). 0 of 2 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 113 m² for D–G; the most common build period is 2012 onwards for C+ and 1950–1966 for D–G; 37% 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) | −9% | — |
| Whole price, nothing held equal | −19.8% | −24.4% to −15.1% |
| Same floor area | −6.8% | −9.1% to −4.4% |
| + same property type | +3.1% | +0.6% to +5.8% |
| + same build period | +5.4% | +2.4% to +8.4% |
| + same year of sale | +3.4% | +0.6% to +6.2% |
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 AL9
| Sector | Sales | Raw gap | Like-for-like | 95% range |
|---|---|---|---|---|
| AL9 5 | 518 | +1% | +3.5% | −0.5% to +7.7% |
| AL9 6 | 162 | −6% | too few | — |
| AL9 7 | 938 | −5% | +1.1% | −2.4% to +4.7% |
▲ 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 AL9
| EPC band (last certificate before sale) | Sales | Median £ per m² |
|---|---|---|
| A | 2 | too few |
| B | 269 | £4,478 |
| C | 419 | £5,092 |
| D | 659 | £5,123 |
| E | 216 | £5,393 |
| F | 49 | £6,359 |
| G | 4 | too few |
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.