Google publishes a measured per-prompt footprint for Gemini

Google's technical paper "Measuring the environmental impact of delivering AI at Google Scale" is the most detailed per-prompt disclosure from any large provider. Using May 2025 production data it reports a median Gemini Apps text prompt at 0.24 Wh, 0.03 gCO₂e and 0.26 mL of water under a comprehensive boundary (active chips, idle capacity, host CPU/RAM, data-centre overhead), versus 0.10 Wh under the narrow active-chip method most prior estimates used.

Over the previous twelve months the energy and carbon of the median prompt fell 33× and 44× respectively.

Limits: the study is self-reported and not third-party verified, water is derived from fleet WUE rather than measured, and off-site water for electricity generation is excluded — the omission UC Riverside's Shaolei Ren flagged to The Verge. The index rewards the disclosure and notes the scope difference against Mistral's full-scope 45 mL figure.