WP#49 - PUE: A Comprehensive Examination of the Metric

Overview

The document is The Green Grid's consolidated reference on Power Usage Effectiveness (PUE) and supersedes its earlier PUE papers. It covers the definition, measurement levels and points, mixed-use and specialized facilities, reporting conventions, partial PUE and the treatment of reused energy. The full text requires sign-in (it is also sold as a book through ASHRAE); this page relies on public summaries only.

PUE is total facility energy divided by IT equipment energy, preferably computed on annual energy (kWh) rather than instantaneous power; DCiE is the inverse of PUE, expressed as a percentage. There are three measurement levels: Level 1 basic (IT measured at UPS output), Level 2 intermediate (at PDU output) and Level 3 advanced (at IT equipment input), with measurement frequency rising with the level.

Partial PUE (pPUE) is the sum of a zone's IT energy and infrastructure energy divided by that zone's IT energy, used for containers or sub-systems. The document's stated limit is that PUE measures infrastructure overhead, not IT efficiency or productivity, and it is not a stand-alone comprehensive efficiency metric.

Key points

1. PUE = total facility energy / IT equipment energy, preferably annual energy (kWh) rather than instantaneous power.
2. DCiE = 1/PUE (as a percentage).
3. Level 1: IT at UPS output; Level 2: at PDU output; Level 3: at IT equipment input.
4. Measurement frequency increases with the level.
5. pPUE = (zone IT energy + zone infrastructure energy) / zone IT energy.
6. PUE is not a productivity metric nor a stand-alone comprehensive efficiency metric.

Using it in design

• Make the default PUE output an annual energy-based PUE from an hourly (8760) simulation, labelled with its measurement level (design estimate: 'L3-equivalent model').
• Provide pPUE per hall or zone and DCiE as a secondary display.
• Never present peak-power PUE as annual PUE; label instantaneous values clearly.

Who should read it

Design engineers and operations teams who calculate or report PUE.

Related standards

• ISO/IEC 30134-2
• EN 50600-4-2
• ASHRAE Datacom Series: PUE

Publication details

Authors

Victor Avelar; Dan Azevedo; Alan French

Publisher

The Green Grid

Year

2012

Document number

WP 49

Document language

English

Source type

Industry body

Access

Citation only

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation