CarboneWatch is a small application that lives in your computer's menu bar. It watches which AI services your machine uses, and estimates their electricity use and carbon footprint, continuously. This page says the essentials in plain words; the scope, sources and limits are in the methodology.
When you use ChatGPT, Claude, Perplexity or a coding assistant, your computer exchanges data with the service's servers. CarboneWatch sees those exchanges — their volume, never their content — and recognises the service by the address it talks to.
From the volume exchanged, it estimates the work asked of the server, the electricity that work consumes, then the matching CO₂ according to the country where the server runs. The result is shown per service, per hour and per day, on your machine.
The extension for Chrome, Edge and Firefox runs the same calculation for what goes through the browser. It works on its own, without the application, or alongside it: it then hands over what it saw, and the application adds up the whole machine.
It reads no conversation, no text, no image. It decrypts nothing, installs nothing hidden, asks for no special rights and creates no account. Nothing leaves your machine unless you choose to contribute to the shared footprint — it is off by default, and what is sent is described before you accept.
It is an estimate, not a measurement. Nobody outside the providers knows exactly how much electricity one request consumes, and the few providers who publish a figure give an average. CarboneWatch starts from what can be measured on your machine and applies factors taken from published studies, our own measurements and a few hypotheses, documented in the methodology dossier available on request.
For any given hour, the figure may be far from the truth, and the methodology says by how much for each factor. Its value lies elsewhere: making uses comparable with one another, showing an order of magnitude where there was nothing, and never hiding its uncertainty.
Some widely used services escape the application, because counting them on the network would give a wrong figure. Gemini shares its addresses with Gmail and Drive: there is no way to tell a question to the AI from a photo backup without reading the traffic. The optional browser extension counts it on its web pages.
The same goes for the AI slipped into everyday tools — Canva, Notion, Microsoft 365, Adobe. It talks to the same addresses as the rest of the tool; only Copilot in Microsoft 365 on the web is counted, by the extension. CarboneWatch would rather state an absence than invent a figure, and the list of those absences is public.
The rule holds everywhere: a service is counted only if what it exchanges is surely the work of an AI. The website of an image generation tool, where people also browse a gallery or manage their account, is recognised but not counted: a figure that is too low and says so beats one inflated by what was not AI.
Using AI has an energy cost that shows up on no bill. What we cannot see, we do not question. CarboneWatch makes it visible, without claiming a precision it does not have, and states its scope, sources and limits so that anyone can judge the figure — and challenge it.
