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Step 4 of 10

The data center

How much energy does it take to answer one question?

Make a guess

A data center uses water. What is it mostly for?

  • Cleaning the machines.
  • Cooling the machines, and some of it evaporates.
  • Nothing: a data center only uses electricity.

Show the answer

The answer: Cooling the machines, and some of it evaporates.

Chips heat up as they compute. Many data centers cool them with water, and part of that water evaporates and doesn't come back. The power plants that make their electricity use water too.

What happens

  1. A data center is a big building full of metal cabinets called racks. The racks hold servers, and the servers hold chips that compute.

  2. Your question doesn't go in alone. A program called the inference server batches it with other people's questions, so the chip never runs half empty.

  3. Inside a rack, the chips pass their results along copper cables. From one rack to the next, they talk through fibers, in flashes of light.

  4. They get hot: it takes electricity to compute, then to carry the heat away, often with water. For one text prompt sent to Gemini, Google counts Energy of a median text prompt sent to GeminiAI chips, server processor and memory, idle standby machines, cooling and electrical losses of the data center; excludes training, data storage, the network and your phoneSource: Google, Measuring the environmental impact of delivering AI at Google scale (arXiv 2508.15734) (August 21, 2025)Read at the source, from the organization that produced it., the whole data center included, and Water used for a median text prompt sent to GeminiWater evaporated to cool Google's data centers; excludes the water of power plants and of chip manufacturingSource: Google, Measuring the environmental impact of delivering AI at Google scale (arXiv 2508.15734) (August 21, 2025)Read at the source, from the organization that produced it. of evaporated water.

  5. Where does this chip come from? Far away: usually designed in the United States, mostly made in Taiwan, with Dutch machines for the finest patterns.

Takeaway

In the data center, your question shares a chip with other people's. The computing has a physical cost: electricity to compute and to cool, and water. Every number depends on what it counts, so the site gives its source and its scope.

Go further

Questions add up

One question takes little, but there are a great many of them. Across all uses, AI included, the world's data centers used Electricity used by the world's data centers in 2025, up 17%IEA estimate; the same report says "almost 500 TWh" and slightly more than 1.5% of world demandSource: International Energy Agency, Key Questions on Energy and AI (April 2026)Read at the source, from the organization that produced it. in a year. By the end of the decade, the International Energy Agency expects roughly twice that: Projected electricity use of the world's data centers in 2030, base caseA projection, not a measurement; April 2025 gave 945, and the extreme cases of that report ranged from 670 to 1,260 TWh in 2030Source: International Energy Agency, Key Questions on Energy and AI (April 2026)Read at the source, from the organization that produced it..

How efficient a data center is

A data center doesn't give all its electricity to the computing machines: some goes to cooling, and some is lost along the way. The ratio of total electricity to what the machines get is called PUE. According to Uptime Institute's worldwide survey, data centers average Average data center power usage effectiveness (total power divided by IT power), averaged per siteUptime Institute global survey 2026, each site counts for one; weighting by site capacity brings the average down to 1.36Source: Uptime Institute, The growing PUE advantage of larger data centers (August 6, 2026)Read at the source, from the organization that produced it.: for every unit of electricity the machines use, the rest of the building takes half as much again. The biggest data centers do better.

A range for water

For the water used by the world's data centers in a year, the IEA estimate is Water used by the world's data centers in 2023, depending on what is counted140 for on-site cooling alone; 560 when adding the water of power plants and energy extraction, and of chip manufacturingSource: International Energy Agency, Energy and AI (April 2025)An estimate: an order of magnitude its own source calls uncertain.. The low end counts only water evaporated on site. The high end adds the water used by power plants and by chip factories. Both ends are correct, each for what it counts, and the last step, "The way back", comes back to this gap.

What Google's measurement leaves out

The Energy of a median text prompt sent to GeminiAI chips, server processor and memory, idle standby machines, cooling and electrical losses of the data center; excludes training, data storage, the network and your phoneSource: Google, Measuring the environmental impact of delivering AI at Google scale (arXiv 2508.15734) (August 21, 2025)Read at the source, from the organization that produced it. per prompt doesn't count training the model, storing data, the network or your phone. Google publishes the number itself, and says no outside organization has checked it.

Around a real data center

The data center in this step is a model. It isn't in any country, and nothing it shows tells you what a data center changes around it. That has to be measured on real cases, at a given date. In Ireland, the national statistics office reads data centers' electricity off the meters. Over a full year, they took Share of Ireland's metered electricity used by data centers in 2025Electricity read from meters, not all the country's energy; 5% in 2015; the same year, homes used 28%Source: Central Statistics Office, Data Centres Metered Electricity Consumption 2025 (July 7, 2026)Read at the source, from the organization that produced it. of it, a little less than all the country's homes.

What a data center costs

A very large AI data center costs Cost of building a 1 GW AI data center, servers includedEpoch's stylized model of a US hyperscaler data center, about two years of construction; servers make up over half of itSource: Epoch AI, Servers account for 60% of the total cost of ownership of a one-gigawatt AI data center (May 14, 2026)An estimate: an order of magnitude its own source calls uncertain. to build, servers included. That's an Epoch AI estimate, based on a typical data center rather than a real project. The servers account for more than half of it.

Sources