About Retrofit Worth

A tool-led UK property-energy site: which streets leak heat, and what insulation and better heating are worth, built on published public records.

Where the data comes from

Two open datasets. The geography (streets, postcodes, areas) and sold prices come from published public sale records. The energy figures come from the public register of lodged energy performance certificates. Both are made available under an open licence, attributed in the footer of every page.

How the figures are produced

Every band distribution, average rating, uplift and estimated saving on this site is computed directly from the certificates we hold – none of it is estimated, modelled or invented beyond the register's own recorded values. We publish only street, postcode and area aggregates over many certificates; we never pair an individual address with a rating, and no property or occupier is identified.

Coverage

We currently hold 47436 sale records and top up both datasets automatically as new data is published. Areas or streets with too few certificates to be reliable – and too few to be safely anonymous – are not indexed.

Stamp duty rates

The stamp-duty calculator uses 2025/26 England & Northern Ireland residential SDLT rates (effective 2025-04-01), sourced from HM Revenue & Customs. If the rates pass their review date, the calculator flags that they may be out of date.

Disclaimer

Figures are for general information only and are not a property valuation, survey, or financial or tax advice.