How much does my ChatGPT use add to my carbon footprint in a year?
About 0.2 kg of CO₂ a year, by Hum’s sums. OpenAI’s own usage paper reports 18 billion messages a week from 700 million users, about 26 each a week. At 0.34 Wh each, that’s about 0.46 kWh a year, or about 0.2 kg on the world-average grid. Even 50 questions a day comes to about 3 kg. An average person’s fossil CO₂ is about 4.8 tonnes a year. This counts answering questions only, not training models, making chips or building data centres.
The bigger pictureOne person’s share is small, but the total keeps growing: electricity use by AI-focused data centres grew 50% in 2025, by the IEA’s estimate.
What nobody knows yet
- Use is very uneven, and OpenAI gives only an average.
- The grids behind ChatGPT’s data centres aren’t published, so the world average stands in.
- Training, chips and buildings aren’t counted here.
Sources (7)
- NBER Working Paper 34255 (OpenAI and Harvard), How People Use ChatGPT Measured
“By July 2025, 18 billion messages were being sent each week by 700 million users, representing around 10% of the global adult population.”
Quote checked on the page, 18 Oct 2026 - OpenAI (Sam Altman; average query, method not published) Company says so
“the average query uses about 0.34 watt-hours, about what an oven would use in a little over one second”
Quote checked on the page, 2 Oct 2026 - Ember, Global Electricity Review 2025 Measured
“Emissions intensity dropped by 2.3% to 473 grams of CO2 per kilowatt hour (gCO2/kWh)”
Quote checked on the page, 2 Oct 2026 - Global Carbon Project Estimated
“The 2025 Global Carbon Budget projects 38.1 billion tonnes of fossil carbon dioxide (CO2) emissions this year.”
Quote checked on the page, 18 Oct 2026 - United Nations Measured
“On 15 November 2022, the world’s population reached 8 billion people, a milestone in human development.”
Quote checked on the page, 18 Oct 2026 - IEA, Key Questions on Energy and AI (2026) Estimated
“Electricity consumption from AI-focused data centres grew even faster, surging 50% in 2025.”
Quote checked on the page, 3 Oct 2026 - Our World in Data (UK government factors) Estimated
“A domestic flight emits 246 grams per kilometer.”
Quote checked on the page, 18 Oct 2026
Hum’s sums
- 18 billion ÷ 700 million ≈ 26 messages each a week
- 26 × 52 weeks × 0.34 Wh ≈ 0.46 kWh a year
- 0.46 kWh × 473 g/kWh ≈ 0.2 kg of CO₂ a year
- 50 questions a day × 365 × 0.34 Wh × 473 g/kWh ≈ 3 kg of CO₂ a year
- 38.1 billion tonnes ÷ 8 billion people ≈ 4.8 tonnes each
- 246 g × 1,000 km = 246 kg of CO₂e per passenger
Cite this
NBER Working Paper 34255 (OpenAI and Harvard), How People Use ChatGPT, as quoted in Hum, “How much does my ChatGPT use add to my carbon footprint in a year?”, https://humearth.org/q/my-year (quote checked 18 Oct 2026).
Cite the original source first; Hum is where you found it.
What do Wh, kWh and TWh mean?
Wh is a watt-hour: a 1-watt light left on for an hour. 1 kWh = 1,000 Wh, and 1 TWh = 1 billion kWh. Hum compares each number with something everyday so you don’t need the units.
Send this answer
A typical ChatGPT user’s year of questions: about 0.2 kg of CO₂ (Hum’s sums from OpenAI’s figures). The build-out behind it is growing fast: AI data centres used 50% more electricity in 2025.