Which AI models are most energy efficient?

Capability is Epoch AI's Epoch AI / Capabilities Index, a single score combining 58 separate tests, coding, using tools, holding a long document in mind, writing and science reasoning among them. It runs from roughly 55 to 170. We use the composite rather than any one test because a model can be excellent at science questions and mediocre at everything else. A handful of older models have no index score; we leave their capability blank rather than filling it from a different test, which would put them in the wrong place in the order.

Energy is calculated, not metered, no AI company publishes per-answer energy. We use the EcoLogits model, which works from how much of a model fires per word and how many words it writes: a 7,000-word-ish answer for a complex prompt, 300 for everyday chat, on a world-average electricity grid.

Calibration. The raw formula assumes a model has hardware largely to itself, which overstates real energy use. We corrected it against 46 samples vs ML.ENERGY on B200, batch 32-128, applying a factor of 0.53518.

Every model is calculated the same way, including those we have lab measurements for. Measured figures swing eightfold with how many requests a server handles at once, and only exist for open models, so using them directly would rank serving setups, not models. They are used to check our work instead.

Day-one estimates are models whose makers have never published a size. We bracket it from comparable models, so those bars are wide on purpose. The largest figures on this page carry the most uncertainty.

Hidden thinking. 65 of the models here generate reasoning text you never see. OpenAI, Anthropic and Google all confirm they bill for it while returning only a summary, or nothing. Our figures count a fixed answer length, so for those models the number shown is an understatement, not an estimate. Each one is marked in the table.

Sources. Epoch AI (capability, model sizes, roster), EcoLogits (energy model), ML.ENERGY (laboratory measurements). All public, all free.

Reuse. These figures are published under CC BY 4.0, use them anywhere, including commercially, as long as you credit The AI Footprint and link back. Read the full methodology →

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