ISO/IEC 30134-6:2021

Overview

ISO/IEC 30134-6:2021 defines the Energy Reuse Factor (ERF) as a key performance indicator (KPI) for data centres. ERF quantifies how much of the energy consumed in a data centre is beneficially reused outside the data centre boundary. ERF = energy reused ÷ total energy consumed (annual basis). The standard clarifies scope, measurement boundaries, reporting formats and examples to ensure consistent, auditable calculation of data centre energy reuse.

Key topics and requirements

• ERF definition and purpose: Establishes ERF as a KPI to report externally reused energy (not the efficiency of the reuse process).
• Data centre boundary and handoff point: Requires defining the point where energy is handed off to another party (utility handoff) and including all energy carriers (electricity, fuel, chilled water, conditioned air) at that boundary.
• Inclusion rules: Count only energy that leaves the data centre boundary for beneficial use outside the site. Internal reuse (within the data centre) must be excluded to avoid double counting with PUE.
• Energy streams and symbols: Standardizes terms (EIT, EEXCESS, EREUSE, etc.) and the types of energy flows to be measured.
• Measurement and calculation: Specifies how to determine ERF using annual energy values and references measurement points; includes guidance on measurement of total energy and excess energy.
• Reporting and public disclosure: Defines a standard construct for communicating ERF data, required reporting elements and recommended trend-tracking data for transparency.
• Annexes: Informative examples of ERF use cases and energy conversion factors to support practical implementation.

Practical applications and users

Who should use ISO/IEC 30134-6:2021:

• Data centre operators and facility managers implementing waste heat recovery, district heating links or mixed-use building integrations.
• Sustainability and ESG teams reporting energy reuse metrics to stakeholders.
• Architects and MEP engineers designing heat-reuse and energy integration systems.
• Auditors and certifiers validating energy reuse claims and public KPIs.
• Building owners and operators negotiating energy handoff agreements with third parties (e.g., district heating utilities).

Typical use cases:

• Benchmarking energy reuse performance across sites.
• Supporting business cases for waste heat recovery or combined heat-and-power (CHP) projects.
• Public reporting of sustainability metrics alongside PUE.
• Contractual and regulatory disclosure of reused energy delivered to external users.

Related standards

• ISO/IEC 30134-1 - Overview and general requirements for data centre KPIs
• ISO/IEC 30134-2 - PUE (Power Usage Effectiveness) specification (used for aligned boundary definitions)
• ISO 8601-1:2019 - Date/time representations referenced for reporting

ISO/IEC 30134-6:2021 provides a standardized, transparent method to quantify and report data centre energy reuse, helping operators demonstrate real-world reductions in primary energy demand and support circular energy economy projects.