An individual property can provide a useful case study without establishing the cost of improving every home. In July 2023, LandlordZONE editor Nigel Lewis described the energy assessment of his own rental flat in south-west London. The account concerned a two-bedroom ground-floor garden property in a building dating from the 1890s.
The flat had previously received a relatively weak D rating. Lewis sought an assessment with energy-efficiency consultant James Tanner after replacing an ageing boiler that had begun leaking. The replacement was prompted by the equipment’s condition, rather than a project designed solely to change the certificate band.
According to the article, the property subsequently achieved a C rating. Lewis reported a £3,000 invoice covering supply and installation of the boiler. That bill described his particular work at that time; it was not a general quote for bringing any D-rated property to C.
The assessment still identified weaknesses elsewhere. The account referred to uninsulated walls, older double glazing and draughty floors. It also reported separate indicative costs for other improvements that were not necessary to reach the band described in this case. Achieving a certificate threshold did not mean that every aspect of the building had been upgraded.
The author also noted continuing carbon emissions. That distinction matters: a certificate rating is not a statement that a property has no emissions or that it will deliver a fixed bill for every occupier. The article did not provide a controlled comparison of annual running costs before and after the work.
Some of the original discussion concerned proposed rental-energy rules and possible deadlines. Those expectations belonged to the 2023 policy debate and are not reproduced here as current legal duties. This retrospective focuses on the documented case described by the author.
The lesson is the importance of a property-specific assessment. One relatively limited replacement was reported to change this flat’s rating, while other buildings may require different work. The archive records that outcome without recommending a heating technology, promising a similar cost or treating a single experience as a national estimate.