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Data centres use electricity to run servers, storage and networking equipment, and to operate the systems that keep that equipment cool and stable. Cooling moves heat out of the building and may consume water directly; electricity generation can add a separate, indirect water footprint. UPS batteries bridge power interruptions, while standby generators can supply power for longer outages. The amounts vary by site, equipment, cooling design, climate and electricity supply.
Where a data centre’s electricity goes
Servers process and store data, using CPUs and, in some facilities, specialized accelerators such as GPUs. Storage systems and networking equipment also need power. Facility infrastructure—including cooling and environmental controls—uses additional electricity to keep IT equipment operating within suitable temperature and humidity conditions.
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For 2024, the International Energy Agency (IEA) estimates that data centres worldwide used about 415 terawatt-hours (TWh) of electricity, approximately 1.5% of global electricity consumption. It estimates that data-centre electricity use grew by 12% annually over the preceding five years. These are global estimates, not figures for every individual facility. IEA, Energy and AI (2025).
IT equipment and cooling
The IEA’s approximate breakdown for modern data centres puts servers at around 60% of electricity use, storage at around 5%, and networking at up to 5%. Cooling can range from about 7% in efficient hyperscale facilities to more than 30% in less-efficient enterprise facilities. The shares are indicative and depend on the facility and its installed equipment; cooling does not have one universal percentage.
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Power Usage Effectiveness (PUE) describes the relationship between facility power and IT-equipment power: it is total data-centre power divided by the power used by IT equipment. A PUE of 2 means the facility uses twice as much power in total as its IT equipment uses. PUE is a facility-efficiency ratio, not a measure of sector-wide electricity consumption or water use. The Congressional Research Service (CRS) explains the metric in its overview of data centres. CRS, Data Centers and Their Energy Consumption.
What projections say—and what they do not
The IEA’s global Base Case estimates data-centre electricity use at about 945 TWh in 2030, just under 3% of projected global electricity consumption. That is a scenario, not a measured future outcome; the IEA also models alternatives because adoption of AI, hardware efficiency and infrastructure constraints could change demand.
A separate U.S.-only projection from Lawrence Berkeley National Laboratory (LBNL), updated in June 2026, gives a 2030 reference estimate of 649 TWh, with a compounded-uncertainty range of 521–843 TWh. In that analysis, data centres could account for 11.8% of total U.S. electricity use in 2030, with scenarios from 9.5% to 15.3%. These U.S. figures and the IEA’s global estimate have different geographies and modeling assumptions; they are not competing estimates of the same total. LBNL, 2024 United States Data Center Energy Usage Report (2026 update).
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesHow data-centre cooling uses water
Cooling removes heat produced by computing equipment. Some systems use water onsite to transfer heat, including evaporative cooling. In a cooling tower, water evaporates as heat is released; additional water replaces what evaporates, and some is discharged as blowdown to limit the buildup of scale and dissolved material.
There are two distinct water-use boundaries to consider:
- Direct water: water consumed onsite, often for cooling.
- Indirect water: water consumed in generating the electricity that powers the data centre.
A facility can reduce direct water use while increasing cooling electricity, or use a power supply with a different indirect water footprint. Those outcomes depend on the cooling system, location and electricity mix. LBNL’s water modeling accounts for onsite cooling and electricity generation across different cooling designs and power-supply scenarios. LBNL, water use in data centres.
Why location changes the water picture
Climate affects cooling needs, while local water availability affects the consequences of direct consumption. The electricity supply also matters because power generation can use water far from the data-centre site. A useful comparison therefore considers direct onsite water, cooling electricity, indirect water associated with power, local water stress, and the facility’s computing density—not simply whether a system is labeled “air-cooled” or “water-cooled.”
A 2021 study by LBNL researchers found that one-fifth of U.S. data-centre servers’ direct water footprint was in moderately to highly water-stressed watersheds. It also found that nearly half were fully or partly powered by plants in water-stressed regions. Those are findings from that study and year, not a current census of all U.S. facilities. Nature Sustainability, 2021 study.
To convey scale, CRS relays an IEA illustration that a 100-megawatt U.S. data centre could consume direct water comparable to about 2,600 households, averaged across cooling strategies; including indirect water from power generation raises the comparison to about 6,500 households. These are contextual comparisons attributed by CRS to the IEA’s 2025 report, not a standard for every 100 MW facility. CRS overview.
Cooling approaches have trade-offs
Direct liquid cooling can carry heat away close to high-performance computing equipment. Central air-handling systems condition air in the equipment space, and free cooling can take advantage of favorable outdoor conditions in some climates or seasons. Facilities may combine approaches. The best choice depends on site conditions and computing requirements; a lower direct-water figure alone does not establish lower total environmental impact.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How UPS batteries and generators keep power available
Data centres are designed for high availability, so they need a response to power interruptions. A UPS (uninterruptible power supply) provides a battery-backed continuity and power-conditioning layer. Standby generators can then supply power for longer interruptions. The exact electrical architecture varies by facility; CRS notes that UPS strategies can range from full standby to active regeneration.
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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →The IEA describes UPS batteries and backup generators as rarely used but necessary for the high reliability data centres must meet. They serve different roles in continuity planning: batteries can bridge a disruption, while generators provide standby generation. IEA, Energy and AI (2025); CRS overview.
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