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Meter points: the boundary is the contract

The same workload uses very different amounts of energy depending on where you measure it. JL-26 makes every figure name its boundary.

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Reviewed 3 November 2026

The four meter points

Joule Ledger meter points
PointBoundaryIncludesFair comparison
M1Device or substrateThe chip, or a living-neuron culture and its electrode arrayChip versus chip
M2Module or boardPlus memory, power conversion and supporting electronicsBoard versus board
M3Unit or rackThe complete system at the wall, as in the MLPerf Power data-center boundary, which excludes cooling and storage nodesSystem versus system
M4FacilityPlus cooling, power conversion losses and life supportFacility versus facility; Overhead Ratio

Matched comparisons only

Comparisons shall use the same meter point on both sides. A device figure at M1 shall not be compared with a facility figure at M4. Most misleading efficiency claims come from mismatched boundaries; see how energy metrics get gamed.

Instruments

  • At M1 to M3, a SPEC-accepted power analyzer controlled through PTDaemon from a separate controller, with clocks synchronized by NTP, as in MLPerf Power (Tschand et al., MLPerf Power).
  • A ranging run precedes the measured run, and ranges stay fixed afterwards.
  • Each measured window lasts at least 60 seconds; shorter tasks are looped.
  • On-board counters count as Measured only after they are validated against an analyzer on the same system; otherwise they are Estimated.

Facility figures

At M4, annual Overhead Ratio claims need at least 12 months of integrated energy, following industry practice for trailing-twelve-month PUE.

Questions

Which meter point should we use?

The one that matches the decision you are making: M1 or M2 to choose hardware, M3 to compare systems, M4 to manage a facility. Many audits report more than one.

Sources

  1. Tschand et al., MLPerf Power

Keep reading

Overhead Ratio (PUE)The JL-26 Overhead Ratio, facility energy over system energy: equal to PUE for data centers, calculated from energy over a period per ISO/IEC 30134-2:2026.How to measure AI inference energyHow to measure the energy of AI inference properly: task set, quality gate, meter point, analyzer, ranging, 60-second windows, closure check and reporting.AI energy benchmarks comparedMLPerf Power, the AI Energy Score and the ML.ENERGY benchmark compared: what each measures, where its boundary sits, and how the Joule Ledger relates.Labels and gradesHow JL-26 labels every energy result (Measured, Estimated, Projected), grades who checked it (Declared, Witnessed, Replicated) and labels science claims.

Take the next step.

The four Joule Ledger meter points, from chip (M1) to facility (M4), what each includes, and why figures from different boundaries cannot be compared.

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