Data shows it can cost around £6,000 to upgrade a terrace house from band D to band C. Flats are cheaper, and estimated to cost about £3,600. Band D homes could save £200 a month in bills, while lower-ranked homes could potentially save more than £1,000.
We've heard nothing from industry about which of those scenarios might happen with the RTS switch-off, and it could be a combination of different issues.