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1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minuteEstimate a data centre’s electricity use by dividing total facility energy by IT equipment energy to calculate power usage effectiveness (PUE). Estimate its water intensity by dividing annual site water use by IT equipment energy to calculate water usage effectiveness (WUE). Use figures from the same reporting period and facility boundary, and identify which inputs are measured versus modeled.
Set the period and facility boundary first
Choose a reporting period before collecting figures. A full year is preferable when the goal is to account for seasonal cooling changes and fluctuations in IT load. Facility electricity, IT energy, and water records should cover that same period.
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Define which loads and water uses belong to the data centre. For a dedicated facility, the U.S. Department of Energy (DOE) says to include all energy use inside the building boundary. In a mixed-use building, shared ancillary services may be excluded, but services dedicated to data-centre operation should be included. Document how shared loads are allocated. DOE’s task-force guidance discusses these boundary choices.
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Collect matching energy and water inputs
Facility and IT energy
Gather total facility energy and IT equipment energy from meters, utility records, or documented engineering estimates. Use a consistent unit, ordinarily kilowatt-hours (kWh), and ensure both figures cover the same boundary and period. Facility energy includes the supporting infrastructure serving the data centre, not only the servers and other IT equipment.
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Site water
Gather site water use for the same period from water or cooling-system meters or utility records. State whether the figure represents water supplied or withdrawn, water consumed, or another explicitly defined flow. These are not interchangeable quantities.
For a cooling tower, makeup water enters the system; some water evaporates as heat is rejected, while some leaves as blowdown to control dissolved minerals. A total input reading and a consumption estimate answer different questions. DOE’s cooling-tower guidance describes these flows and their management.
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Calculate PUE and WUE
| Metric | Calculation | What it indicates |
|---|---|---|
| PUE | Total facility energy ÷ IT equipment energy | Facility-infrastructure energy relative to IT energy; dimensionless |
| WUE | Annual site water use ÷ IT equipment annual energy | Site water intensity; DOE expresses it in liters per kWh |
Use annual kWh in both parts of the PUE calculation. For WUE, divide liters of site water over the reporting year by IT energy in kWh over that same year. DOE defines both denominators as IT equipment energy, so results are comparable only when period, boundary, and accounting method align. See the DOE data-centre efficiency guidance and its metric definitions and boundary guidance.
Show assumptions and uncertainty
Label the result as an estimate if any input is modeled rather than metered. Show the inputs, reporting period, boundary, units, allocation method for shared services, and water-flow definition. Missing readings or engineering assumptions can materially affect the result; do not imply meter-grade precision where it is not supported.
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A suitable water flow meter may help fill a gap when reliable utility or site-meter records are unavailable. Its range, pipe size, installation, and calibration need to match the system. DOE’s metering best-practices guide emphasizes measured energy where available and provides calculation examples using metered inputs. A consumer meter should not be presumed suitable for industrial cooling equipment.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Interpret the result without overclaiming
A lower PUE indicates less facility energy overhead relative to IT energy, but it does not measure useful computing output or overall data-centre efficiency on its own. DOE recommends considering multiple metrics, including PUE-family measures and utilization where relevant.
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DOE’s 2024 design guide labels PUE of 1.6 “standard,” 1.4 “good,” and 1.1 “better”; these are guide benchmarks, not universal targets for every site. The same guide cites Uptime Institute’s 1.55 average PUE for large data centres in 2022, a figure tied to that survey year. Neither benchmark replaces a like-for-like comparison of actual facilities. DOE’s 2024 design guide provides the dated benchmark context.
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Compare sites or scenarios using the same period, boundary, and metering approach. Report PUE and WUE separately, and describe whether cooling is evaporative, recirculated, or air-cooled. Because water-use boundaries and cooling designs differ, one metric alone cannot establish which site is more efficient overall. No broadly comparable WUE benchmark across data-centre types is established by the cited guidance.
Water-management figures are not universal estimates
DOE’s 2019 FEMP guidance reports that increasing cooling-tower cycles of concentration from three to six reduces makeup-water requirements by 20% and blowdown by 50%. Those are operational figures in that guidance, not a general forecast for every facility. Applying them to a particular site requires knowing its cooling system and operating conditions. DOE’s cooling-tower management guidance provides the context.
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