Question to the Department for Business, Energy and Industrial Strategy:

To ask Her Majesty's Government, further to the Written Answer by Lord Callanan on 7 July (HL6124), whether they can answer the question put with regard to stored passive flue gas heat recovery technology rather than passive flue gas heat recovery technology.

The response I gave to the noble Lord on 7 July 2020 to Question HL6124 applies to passive flue gas heat recovery systems with and without thermal storage.

Analysis undertaken on behalf of BEIS showed that the typical household could increase boiler efficiency between 1% to 5% by adding a passive flue gas heat recovery system. The 1-5% boiler efficiency level includes both product types with the 5% being an upper maximum for a passive flue gas heat recovery device with thermal storage (typically a 5 to 10 litre store) in a large house.