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To assess a proposed data centre, ask for its projected annual electricity and water volumes, the boundaries and assumptions used to calculate them, and evidence about the cooling design and local grid and water conditions. Use PUE and WUE to compare efficiency—not as substitutes for absolute demand or a site-specific impact assessment.
Start with projected annual demand
Ask the developer to provide projected annual total facility electricity use and IT equipment energy use, with the forecast period and operating assumptions stated. The figures should make clear which loads are included and where the measurement boundary lies. A proposal that supplies only an efficiency ratio does not establish how much electricity the facility is expected to consume.
Request the same level of detail for water: projected absolute water input, the sources supplying it, the uses included, and the conditions assumed for the forecast. The EU framework defines water input as water volumes entering the data-centre boundary and used in relation to its functions. Its reporting method is set out in Commission Delegated Regulation (EU) 2024/1364.
- Forecast period: Identify the years covered and whether the estimate describes a ramp-up period, a typical operating year, or another scenario.
- Operating assumptions: Ask what operating conditions the estimate assumes and whether figures are modeled, measured, or aspirational.
- Included loads and uses: Have the developer identify which facility electricity loads and water sources or uses are inside the reported boundary.
- Like-for-like basis: When comparing proposals, align the forecast periods, operating assumptions, reporting boundaries, and metric definitions.
What PUE and WUE tell you—and what they leave out
The EU framework defines Power Usage Effectiveness (PUE) as total data-centre energy divided by IT equipment energy. It describes supporting energy relative to IT energy: lower PUE indicates less supporting energy per unit of IT energy. It does not, by itself, show the facility’s absolute electricity demand. A highly efficient large facility can still have substantial total electricity use.
Water Usage Effectiveness (WUE) is water input divided by IT energy under the EU framework. Read it alongside the projected water volume, water source, cooling approach, and local conditions. A WUE value alone cannot tell you whether the facility’s total withdrawals or consumption are compatible with local resources.
The framework also includes two other indicators: Energy Reuse Factor (ERF), energy reused divided by total facility energy, and Renewable Energy Factor (REF), renewable energy divided by total facility energy. These can help describe energy reuse and renewable energy, but neither establishes whether a particular grid or water source can support a proposed facility. The Commission’s overview of the reporting system and indicators is available on its energy performance of data centres page.
Examine cooling and the site’s water context
Ask the developer to describe the cooling design and connect that description to its water forecast. The European Commission says water consumption depends primarily on cooling technology, and that climate affects WUE: cooler regions generally need less water cooling, while warmer regions may rely on it more. A generic statement about a cooling system is therefore not enough; the proposal should explain how its design and site conditions produce the stated water demand.
Also ask where the water will come from and whether the forecast accounts for the proposed site’s conditions. Public sector-wide indicators can provide context, but they cannot establish that the local source has adequate availability or that the proposal’s use is acceptable. Those questions require site-specific evidence and locally applicable review.
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Compare proposals on consistent terms
For multiple proposals, compare more than efficiency scores. Put the same categories side by side and check that each developer uses comparable assumptions and measurement boundaries.
| Comparison item | What to request or check |
|---|---|
| Electricity | Projected annual total facility electricity and IT equipment energy, including the forecast period, assumptions, and loads included. |
| PUE | Reported value, definition, reporting period, and the total-facility and IT-energy boundaries used. |
| Water | Projected annual water input, sources and uses included, forecast assumptions, and measurement boundary. |
| WUE | Reported value, definition, reporting period, and relationship to the stated water volume and IT energy. |
| Cooling and location | Cooling design, climate assumptions, water source, and evidence about local water conditions. |
| Energy reuse and renewables | How reused heat and renewable energy are treated, including ERF or REF where reported; these do not replace local grid review. |
| Evidence quality | Whether each figure is measured, modeled, or aspirational, and whether the operating assumptions and boundaries are comparable. |
When a proposal uses a different boundary or forecast basis from another, do not treat the resulting ratios or volumes as directly comparable until the difference is explained. A clear comparison should preserve both the efficiency indicators and the absolute resource estimates.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Use EU-wide figures as context, not as a site forecast
The European Commission’s 2026 report says EU data centres consumed 68 TWh of electricity in 2024 and projects 114 TWh by 2030, representing 3.2% of EU electricity demand. The report also gives an average reported EU WUE of 0.58 in 2024, with Member State figures ranging from 0.07 to 1.28. These are EU-wide reported figures; they do not predict a particular facility’s use or local impact. The report notes that electricity typically accounts for over 90% of a data centre’s direct energy use.
The report frames the wider issue this way: “The expanding data centre sector poses a challenge for energy availability, availability of electricity grids, carbon emissions and environmental resources such as water.” This is the European Commission’s wording in its 2026 report on the energy efficiency of data centres in the EU.
Check reporting and local review
The Commission describes an EU database that collects and publishes energy-performance and water-footprint information for data centres subject to reporting. Its published, aggregated information can help put proposals in context, but it is not a substitute for a defensible projection for the specific site.
The cited reporting framework is EU-specific. It does not determine whether a particular site has enough grid capacity or water availability, and requirements vary by jurisdiction. Identify the site and ask the competent planning, water, grid, and environmental authorities which reviews and approvals apply. A proposal’s resource forecast and local review address different questions: one estimates demand; the other considers whether the site and infrastructure can accommodate it.
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