How a Spreadsheet Error Doubled the Tories' Net Zero Cost Figure
Kemi Badenoch's 100-page conference policy document The Right Way puts the cost of net zero almost £500bn too high because of an apparent spreadsheet double-count.
The document, prepared for the Conservative conference in Birmingham, says the Climate Change Committee (CCC), the UK's independent climate adviser, estimated in 2020 that its path to net zero — the point where emissions added and emissions removed balance out — would cost £957bn, citing the Sixth Carbon Budget, the official emissions plan for the mid-2030s The Guardian. In the same section it lists gross economic costs of £1.4tn, falling to £957bn once savings are included.
The Committee's report actually totals £478bn, half the cited figure. The error looks mechanical. A count of costs in a CCC spreadsheet also added in the row that already showed the totals for each column, doubling the sum. The mistake was found by Carbon Brief, which alerted the Guardian The Guardian. Carbon Brief later published a factcheck concluding the UK Conservatives doubled the cost of net zero after a spreadsheet blunder Carbon Brief.
A Climate Change Committee spokesperson said "We don't recognise this number" and said its offer to meet Kemi Badenoch to discuss its advice remains open.
The Committee's latest analysis puts the expected cost of reaching net zero by 2050 at about £110bn, or about £4bn a year, equal to 0.2% of GDP, the total value of the economy. Its supporting analysis for the Seventh Carbon Budget, the plan for the late 2030s and early 2040s, estimates £2 to £4 in benefits for every £1 spent Climate Change Committee. Separately, the Committee's Finance Advisory Group said capital investment — money spent on equipment and infrastructure — in net-zero technologies will need to rise from around £10bn a year to around £50bn a year by 2030, before peaking in 2035 and levelling off Climate Change Committee.
The £957bn figure has been used before. It also appeared in an Institute of Economic Affairs report and a Spectator article.
In The Right Way, the cost claim supports the Conservatives' decision to drop the UK target of reaching net zero emissions by 2050, a legal target introduced under Theresa May. Badenoch published the document, described as a major statement of Conservative principles setting out how the Conservative Party will govern Britain, on 4 October 2026 Conservatives. The text was modelled in part on The Right Approach, produced by Margaret Thatcher's Conservative Party in 1976.
The broader context here is why the maths matters for the politics. The cost estimates carry much of the weight in the document's climate section. They give the numbers-based case for dropping a legal target set by a previous Conservative government. Doubling the figure does not on its own answer whether decarbonisation is expensive or cheap. It does change the budget picture delegates in Birmingham were given to judge that choice.
Looking ahead, three questions will shape the debate. First, whether the party corrects or withdraws the £957bn figure before it appears in speeches, briefings and candidate leaflets. Mistakes of this kind tend to stick once repeated, and earlier use of the same number by the Institute of Economic Affairs and the Spectator points to an easy route for it to spread. Second, how the party deals with the Committee's newer cost path. The gap between £957bn and £110bn is not only the double-count. It also reflects newer analysis, changed technology prices and a different way of counting savings and side benefits. Resource costs, flows of capital investment and net costs to GDP are different things, like the price tag, the loan to pay for it, and the final hit to household income, and they are often mixed together in political debate. The Finance Advisory Group's rise to £50bn a year by 2030 describes investment to be mobilised, much of it private, not a government bill for the same sum. Third, whether the Committee's open offer of a meeting is accepted. Official advisers do not often comment this directly on a party document. The line of non-recognition is narrow and technical, but the signal is wider. For readers who follow Sixth and Seventh Carbon Budget modelling, trust will depend less on conference language than on whether future Conservative numbers use corrected CCC baselines and show gross costs, savings and benefits separately.
