A policy booklet recently published by the UK’s opposition Conservative Party features a prominent financial figure regarding the transition to a net-zero economy that appears to have been inflated by a factor of two due to a basic spreadsheet error.

The policy document, titled "The Right Way" and framed as a "common sense" guide to political strategy, asserts that what voters ultimately want is a government competent enough to solve the practical problems for which it takes responsibility. Within its pages, a specific section argues that sophisticated economic modelling should never serve as a substitute for sound political judgment. To support this thesis, the document takes aim at various official estimates concerning the cost of achieving net-zero carbon emissions in the United Kingdom.

However, the publication makes a factual error by claiming that the Climate Change Committee (CCC)—the government’s official independent adviser on climate policy—had previously estimated the cost of reaching net-zero at nearly £1 trillion. Specifically, the Conservative booklet states: "In 2020, the CCC estimated that its route to net-zero would cost £957bn."

In reality, the CCC’s actual figure published in 2020 was exactly half that amount, standing at £478bn. Furthermore, in subsequent updates, the committee revised its projections downward. Last year, the CCC published a fresh, significantly lower figure of £108bn, driven largely by the rapidly falling costs associated with electric vehicles and renewable energy technologies.

The origin of the £957bn figure can be traced back through a paper trail of third-party reports that inadvertently misinterpreted underlying data published by the advisory body several years ago.

Unravelling the Spreadsheet Error

The Conservative Party’s erroneous citation appears to originate from an analytical misstep in an external report that accidentally added up numbers twice while utilizing a spreadsheet made publicly available by the CCC in December 2020.

The 2020 spreadsheet in question contains a detailed table cataloguing the additional capital investments required to construct a net-zero economy, ranging from low-carbon electricity generation infrastructure to the mass installation of domestic heat pumps and electric vehicles. These extra capital expenditures, designated under the standard accounting label of "CAPEX," accumulate to a total of £1.38 trillion across the 30-year timeframe spanning from 2020 to 2050. Against these capital investments, the model sets operational savings, classified as "OPEX," which amount to £0.90 trillion over the same period.

When these figures are properly balanced and added up over the entire 2020-to-2050 timeline, the combined net total of CAPEX and OPEX figures comes to £478bn.

The root of the error lies in the layout of the spreadsheet. In addition to listing the annual sectoral CAPEX and OPEX figures, the CCC document includes a summary line giving the combined totals for each individual calendar year. It appears that an analyst reviewing the spreadsheet inadvertently added all of these annual sub-totals together alongside the individual sectoral components, resulting in the operational savings and capital costs being counted twice.

This double-counted calculation yields a total of £957bn—precisely the figure that eventually found its way into the Conservative Party’s policy booklet.

When the CCC originally published its Sixth Carbon Budget advice in 2020, it emphasized that the net cost of £478bn amounted to less than 1% of the UK’s total gross domestic product (GDP) over the course of three decades. The committee pointed out at the time that while the initial capital investment requirement was substantial, it would yield significant long-term savings through reduced fossil fuel imports and would ultimately stimulate overall economic activity, boosting GDP by roughly 2%.

By 2025, the committee refined its models further, updating its estimates for investment costs and operating savings to £670bn and £562bn respectively. This resulted in a revised net total of £108bn over the 2025-2050 period, which translates to less than 0.2% of GDP. Earlier this year, the committee reiterated that transitioning to net-zero would ultimately cost less than enduring a single major fossil fuel price shock, noting that the broader economic and societal benefits of the transition would be worth approximately £110bn per year.

The Paper Trail of an Inflated Figure

While the Conservative policy document cites the CCC’s 2020 advice on the UK’s sixth carbon budget as its source, the official budget documents themselves never contained the £957bn figure. Investigative tracking by energy analysts shows that the number first appeared online in January 2026 in an article published by The Spectator, authored by retired engineer and self-described accidental energy analyst David Turver.

Just a day after publishing his article, Turver repeated the inflated figure in a formal report written for the free-market Institute of Economic Affairs (IEA). His report explicitly cited figure 5.3 of the CCC’s 2020 supporting information. However, the underlying spreadsheet containing the data for that specific figure only totals £478bn—exactly half of the amount cited in the report.

Turver’s methodology involved summing up all the figures in the spreadsheet without accounting for the fact that annual summary totals were already embedded within the rows, thereby duplicating the costs. This initial report also sparked a wave of subsequent exaggerated headlines in other publications claiming that net-zero would cost anywhere from £7.6 trillion to £9 trillion. Those even larger figures were based on speculative assumptions that treated fossil fuels, along with the cars, heating boilers, and power plants that consume them, as having zero economic value or cost.

Following the circulation of Turver’s report in early 2026, the £957bn figure was adopted and republished in March by the Great British Think Tank, an organization whose promotional materials emphasize data-driven analysis sourced exclusively from official public bodies. From there, the figure migrated directly into the Conservative Party’s "Right Way" booklet published in October 2026, cementing the spreadsheet mistake into formal political literature.