Published projections are usually quoted as headline totals with the assumptions stripped off, which is what makes them look like disagreements about AI. They are not. Every figure in the table below is a deterministic output of a small set of stated parameters, and the honest way to read a range is to ask what would have to be true for each endpoint to be the wrong one. The four-case framework was set out in the IEA's 2025 Energy and AI report[2] and carried forward, updated, into its 2026 edition.
Both models compute the same identity. Annual energy equals installed capacity multiplied by 8,760 hours and by a capacity factor; total facility energy equals IT energy multiplied by PUE. That means three independent levers set the answer: how much accelerated capacity is installed, how hard it runs, and what the infrastructure overhead costs. Public argument concentrates almost entirely on the first.
The second lever is the one to watch. Across all four of the IEA's cases and every projection year, the published fleet capacity factor sits between 48% and 50% — it is effectively a constant, and it is never sensitivity-tested.[1]Berkeley Lab independently uses 50% when it converts energy to interconnection capacity, and is candid that the figure is weakly evidenced: current utilization of interconnection capacity "is not well documented but is estimated to be around 50% due to high redundancy requirements and maintenance needs."[3] Two institutions converging on the same lightly-sourced constant is not corroboration.
The third lever is quietly load-bearing too. The IEA's Base Case has fleet PUE improving from 1.38 in 2025 to 1.29 in 2030.[1]Uptime Institute's 2025 survey of more than 800 operators reports industry-average PUE essentially flat for about six years.[6] Those two statements are not compatible without a large mix shift toward new-build hyperscale capacity — which is a real effect, but it is an assumption, not an observation.
Sources for Table 1: IEA Key Questions on Energy and AI, Annex A[1]; LBNL 2025 Update, Tables 1–2[3]