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.
Open preview (PDF)Information technology — Data centres key performance indicators — Part 6: Energy Reuse Factor (ERF)
