How a Spreadsheet Error Doubled the 'Cost of Net Zero' in the Tories' Flagship Plan

The Conservative Party's flagship policy document has doubled the official cost of reaching net zero after someone apparently added up a spreadsheet twice, according to a factcheck by Carbon Brief. The error, which inflates the figure by nearly £500 billion, sits at the heart of the party's justification for scrapping Britain's 2050 net-zero target.

The claim appears in The Right Way, a 100-page policy document produced for the Conservative conference in Birmingham and presented as leader Kemi Badenoch's flagship programme. In a chapter on net zero, the document states: "In 2020, the Climate Change Committee estimated that its route to net-zero would cost £957bn." Badenoch repeatedly used the figure in her main conference speech.

The document uses the number to justify abandoning the net-zero-by-2050 target, which was introduced under Theresa May. It argues that estimates of the cost to the economy "have varied enormously", before citing the £957 billion figure as the authoritative 2020 assessment.

What the official numbers actually say

The real figure is exactly half. The Climate Change Committee's 2020 advice on the UK's sixth carbon budget estimated net costs of £478 billion over 2020 to 2050, not £957 billion. The committee's spreadsheet broke the figure into two parts: additional capital expenditure (CAPEX) of £1.38 trillion on everything from low-carbon electricity generation to heat pumps and electric vehicles, set against operational savings (OPEX) of £0.90 trillion. Added together, the two come to £478 billion.

So where did £957 billion come from? In addition to the annual sectoral CAPEX and OPEX figures, the CCC's 2020 spreadsheet also contained a line giving combined totals for each year. Carbon Brief's analysis concludes that someone added all of the numbers together, including that totals row, counting the savings and costs twice. The double-counted total comes to roughly £957 billion, matching the figure in the Conservative document. A CCC spokesperson said: "We don't recognise this number."

At the time of the 2020 advice, the committee said the £478 billion net cost amounted to less than 1 per cent of GDP over 30 years, and that the large investment needed would not only produce savings from lower fossil-fuel imports but would boost GDP overall by around 2 per cent.

The figure is even more out of date than it is wrong

Beyond the arithmetic error, the £957 billion claim relies on a superseded estimate. In 2025, the CCC revised its assessment: investment costs of £670 billion and operating savings of £562 billion, giving a net total of just £108 billion over 2025 to 2050, or less than 0.2 per cent of GDP. The sharp fall was driven largely by the declining cost of electric vehicles.

Earlier this year, the committee went further, saying that cutting emissions to net zero would cost less than a single fossil-fuel price shock and that doing so would deliver benefits worth £110 billion per year. The document's own next line, in fact, gives the newer £108 billion estimate, making the £957 billion figure doubly odd.

How the wrong number travelled

Carbon Brief traced the paper trail of the £957 billion figure. Its earliest online appearance was a 12 January 2026 article in the Spectator by retired engineer David Turver, who describes himself as an "accidental energy analyst". A day later, Turver repeated the mistaken number in a report for the free-market Institute of Economic Affairs, citing figure 5.3 of the CCC's 2020 advice, even though the underlying spreadsheet only adds up to £478 billion.

In March, the figure was repeated by the Great British Think Tank, an organisation whose tagline is "data, not vibes" and which says every one of its figures is sourced from official public bodies. The £957 billion number then appeared in the Conservatives' Right Way document in October 2026. It is possible the party copied the figure without checking it.

The same flawed chain produced even wilder numbers. Turver's report triggered a slew of inaccurate headlines stating that net zero would cost £7.6 trillion, or even £9 trillion. Those figures were based, among other things, on the implicit assumption that fossil fuels, and the cars, boilers and power plants that burn them, are all free.

Why a spreadsheet error matters in politics

The Guardian, reporting on Carbon Brief's findings, noted that the document overestimated the cost of net zero by nearly £500 billion through what appeared to be an accidental double-count. Framing matters: a figure of £957 billion makes decarbonisation sound like a ruinous burden, while the actual £478 billion, and still more the current £108 billion estimate, tells a story of manageable investment with large offsetting savings.

The inflated number was not a footnote. It was the centrepiece of the party's climate messaging at its flagship conference, repeated by the leader in her keynote speech to justify ditching a legally binding target set by a previous Conservative government. Numbers of this size stick in public memory longer than corrections, meaning the error may continue shaping the climate debate even after the factcheck.

The episode also illustrates how misinformation can launder itself through respectable-looking channels. A mistake in a Spectator column became an IEA report, then think-tank analysis, then party policy, with each step lending the number fresh authority without anyone re-checking the original spreadsheet.

What happens next

The CCC has said its offer to meet Badenoch and walk her through the advice remains open. Whether the Conservatives correct The Right Way is unclear; the party had been contacted for comment. For the wider public, the lesson is simpler: when a headline-grabbing cost figure arrives without visible working, ask to see the spreadsheet, and check whether someone has counted the totals twice.

Why it matters

Policy built on a doubled number is policy built on sand. The net-zero target is one of the most consequential economic commitments in British politics, touching energy bills, industry and infrastructure for decades. If the debate is conducted with figures inflated by hundreds of billions of pounds, voters cannot judge the real trade-offs. The spreadsheet blunder is a reminder that in climate politics, as in climate science, the quality of the arithmetic is the quality of the argument.