Badenoch's future homes pledge swaps a £5,000-£8,000 build cost for a retrofit above £20,000

The pledge makes a new home cheaper to build and dearer to run ^[2]. On the Guardian's figures, the £5,000 to £8,000 spent at build comes back through bill savings in roughly four to six years ^[12]. That saving was estimated in 2024, when energy was cheaper, and the Guardian expects it is substantially higher now, so the payback today is probably shorter ^[4]. A household that buys without the measures and fits them later pays more than £12,000 to £15,000 above the build-time cost ^[13].

The strongest case against the standard is the Conservatives' own cost figure. Set their estimate of £30,000 for a new-build house ^[15] against the Guardian's range and it is about four to six times higher ^[16]. At £30,000, a saving of £1,300 a year would take about 23 years to repay the outlay ^[17]. The Guardian did not say where the party's estimates came from.

We think the pledge is a bigger cost decision than the attention it drew at conference suggests ^[1], because of scale. The UK needs approximately 6m new homes ^[3]. If every one were built without the measures and retrofitted later, the extra cost over fitting them at build would exceed £72bn ^[14]. Neither assumption is safe. The 6m is a national need, not one parliament's build programme, and an owner who never retrofits pays through higher bills instead ^[11].

Housebuilders, who carry the build-time cost, have been among the Conservatives' biggest donors, though that giving has fallen off in recent years ^[8]. They have also already spent on getting ready ^[9]. Simon McWhirter, chief executive of the UK Green Building Council, said: "The housebuilding industry has spent years preparing for the introduction of the FHS, investing in skills, supply chains and new products. Reversing course would ... risk slowing progress towards building the homes that people want and need." ^[9]

The sequencing turns the pledge into a reversal. Repeal depends on a Conservative win at the next general election ^[2], and the UKGBC says the industry will have to implement the standard before then ^[7]. A Conservative government would be unwinding rules builders already follow ^[7]. In our view, the cost before the vote is the uncertainty the pledge adds to builders' and suppliers' plans. Jan Rosenow, a professor of climate and energy policy at the University of Oxford, said: "Every home constructed today that runs on fossil fuels is a liability for the occupants. It also results in investor uncertainty and disrupts the supply chain that has been gearing up for this. What we need is less political point scoring and more long-term clarity." ^[6]