Environmental Cost of AI's Energy Use: Carbon, Water and Land Footprints
Richmond Hill, Ontario (CA): United Nations University Institute for Water, Environment and Health (UNU-INWEH) (2026), 55 pp.
Contains 13 figures
ISBN 978-92-808-6141-9
"[...] The study reveals some striking numbers. In 2025, data centers—the physical backbone of AI—consumed an estimated 448 TWh of electricity. If data centers were a country, that level of electricity use would rank it 11th globally. On current trajectories, data center electricity demand could roughly double to 945 TWh by 2030, nearly triple the combined annual electricity use of Pakistan, Bangladesh, and Nigeria, together home to more than 650 million people. Producing that much electricity would have a carbon footprint of 399 million tonnes CO2e, requiring 6.7 billion trees grown over 10 years to offset—roughly twice the number of trees in the United Kingdom. The associated water footprint of 9.3 trillion liters would be equivalent to the annual domestic water needs of all 1.3 billion residents of Sub-Saharan Africa. The land footprint associated with this electricity would exceed 14,500 km², nearly 10 times the size of Mexico City.
AI is now one of the most significant drivers of that data center growth. In 2025, AI workloads alone accounted for around 20% of total data center electricity use, and if that share rises to 40% by 2030 as projected, its electricity demand could reach roughly 378 TWh—enough to meet the residential electricity needs of the entire population of Sub-Saharan Africa for over 2 years. AI’s environmental impacts are shaped not only by data center growth and electricity supply mixes, but also by the escalating cost of building ever-larger models. For example, GPT-3 training consumed an estimated 1.3 GWh of electricity over 34 days, while GPT-4 is estimated to have consumed 50 to 70 GWh over 100 days, roughly 40 to 55 times GPT-3. Yet training is only part of the picture as AI’s operational footprint is increasingly driven by inference. Once models are deployed, billions of everyday interactions account for the bulk of energy use, with inference estimated at roughly 80–90% of total energy consumption.
[...] The report identifies priority implications for key stakeholders. Governments must integrate AI infrastructure into energy system planning, carbon accounting, water governance and land use permitting. This requires standardized environmental footprint reporting so impacts can be verified and compared across providers and jurisdictions. Industry and AI developers should treat model selection, default outputs, and routing decisions as footprint determinants, while also improving efficiency-by-design. Users and deploying organizations also shape impacts through volume, frequency, and modality choices. They should adopt “fit-for-purpose” use: selecting the lightest model and lowestenergy format that meets the task and limiting high-cost features when not needed. Data center operators and utilities should recognize siting and procurement as environmental footprint decisions, apply environmental impact screening and cumulative impact assessment. They should implement transparent mitigation and community safeguards where expansion occurs. Investors and financiers should treat electricity, carbon, water, and land footprints as material risks for AI infrastructure portfolios and use comparable footprint metrics in due diligence." (Executive summary, pages 12-13)
AI is now one of the most significant drivers of that data center growth. In 2025, AI workloads alone accounted for around 20% of total data center electricity use, and if that share rises to 40% by 2030 as projected, its electricity demand could reach roughly 378 TWh—enough to meet the residential electricity needs of the entire population of Sub-Saharan Africa for over 2 years. AI’s environmental impacts are shaped not only by data center growth and electricity supply mixes, but also by the escalating cost of building ever-larger models. For example, GPT-3 training consumed an estimated 1.3 GWh of electricity over 34 days, while GPT-4 is estimated to have consumed 50 to 70 GWh over 100 days, roughly 40 to 55 times GPT-3. Yet training is only part of the picture as AI’s operational footprint is increasingly driven by inference. Once models are deployed, billions of everyday interactions account for the bulk of energy use, with inference estimated at roughly 80–90% of total energy consumption.
[...] The report identifies priority implications for key stakeholders. Governments must integrate AI infrastructure into energy system planning, carbon accounting, water governance and land use permitting. This requires standardized environmental footprint reporting so impacts can be verified and compared across providers and jurisdictions. Industry and AI developers should treat model selection, default outputs, and routing decisions as footprint determinants, while also improving efficiency-by-design. Users and deploying organizations also shape impacts through volume, frequency, and modality choices. They should adopt “fit-for-purpose” use: selecting the lightest model and lowestenergy format that meets the task and limiting high-cost features when not needed. Data center operators and utilities should recognize siting and procurement as environmental footprint decisions, apply environmental impact screening and cumulative impact assessment. They should implement transparent mitigation and community safeguards where expansion occurs. Investors and financiers should treat electricity, carbon, water, and land footprints as material risks for AI infrastructure portfolios and use comparable footprint metrics in due diligence." (Executive summary, pages 12-13)
1. AI ACROSS THE GLOBE, 14
A Technological Explosion -- The Expanding Reach of AI Across Sectors -- The Global Market for AI -- Impacts on the Global Labor Market -- Growing Concerns about AI -- Environmental Dimensions of AI -- A Just and Sustainable AI Future
2. AI'S GROWING ENERGY DEMAND, 25
Energy Intensity of AI Training -- AI's Energy Demand and its Environmental Footprints -- AI's Training Footprints -- Data Centers and AI's Expanding Energy Demand -- AI's Contributions to Data Centers' Energy Use -- World's Top Data Center Hosts and their Energy Mixes -- Local Costs and Distant Benefits
3. AI IN USE: TOOLS AND TASKS, 38
Two Forces Shaping AI’s Operational Footprint -- AI Tasks and their Footprints -- AI Use at Scale -- Conventional Search Versus Enhanced Search -- Efficiency Improvement and Rebound Effects -- Behavioral Energy Costs: Model Choice and User Prompts Matter -- Toward Sustainable Use and Scale
4. THE WAY FORWARD, 46
Guiding Principles for a Responsible AI Ecosystem -- From Measurement to Action -- Roles and Responsibilities -- Putting Principles into Practice
A Technological Explosion -- The Expanding Reach of AI Across Sectors -- The Global Market for AI -- Impacts on the Global Labor Market -- Growing Concerns about AI -- Environmental Dimensions of AI -- A Just and Sustainable AI Future
2. AI'S GROWING ENERGY DEMAND, 25
Energy Intensity of AI Training -- AI's Energy Demand and its Environmental Footprints -- AI's Training Footprints -- Data Centers and AI's Expanding Energy Demand -- AI's Contributions to Data Centers' Energy Use -- World's Top Data Center Hosts and their Energy Mixes -- Local Costs and Distant Benefits
3. AI IN USE: TOOLS AND TASKS, 38
Two Forces Shaping AI’s Operational Footprint -- AI Tasks and their Footprints -- AI Use at Scale -- Conventional Search Versus Enhanced Search -- Efficiency Improvement and Rebound Effects -- Behavioral Energy Costs: Model Choice and User Prompts Matter -- Toward Sustainable Use and Scale
4. THE WAY FORWARD, 46
Guiding Principles for a Responsible AI Ecosystem -- From Measurement to Action -- Roles and Responsibilities -- Putting Principles into Practice