A New Era in Energy Modelling: The Transition from SAP 10 to HEM


As 2025 approaches, the UK is set to introduce the Home Energy Model (HEM), a step forward in building energy assessment, replacing the Standard Assessment Procedure (SAP) 10.2. This transition is aligned with the Future Home Standards, aiming to change how we understand and manage building energy consumption.

Overview of HEM

HEM represents an advancement in energy modelling, offering a more detailed and dynamic approach compared to SAP. With 30-minute calculating intervals, HEM provides a detailed view of energy usage, incorporating various external conditions and ensuring a more accurate representation of a building’s energy performance.

Why Replace SAP with HEM?

The shift to HEM is driven by the need to match international energy modelling standards and to update assessing methods. HEM’s design simplifies the modelling process, making it more user-friendly and adaptable due to “wrappers”. The energy flexibility concept allows the model to adapt and regulate energy use more effectively, enabling smarter energy use.

Comparative Analysis: SAP 10.2 vs. HEM

HEM improves on SAP in many aspects including:

  • Time Resolution: HEM’s 30-minute intervals offer a more detailed view than SAP’s monthly analysis, leading to better accuracy in energy demand modelling.
  • Technology Modelling: HEM effectively models modern energy systems like heat pumps, providing a realistic depiction of their performance under varied conditions.
  • Flexibility and Detail: The enhanced detail in HEM allows for a comprehensive analysis of energy consumption patterns, progressing the development of more effective energy-saving strategies.

Standards and Compliance

HEM aligns with the current international standards, specifically BS EN ISO 52016-1:2017, ensuring its relevance globally. Its design, using advanced coding techniques and “wrappers”, improves transparency and ease of updates, making it a tool that can adapt to an ever-changing climate.

Consultation phase

HEM is currently in a consultation phase, a formative stage used for refining its framework based on industry feedback. This is essential for finalising HEM specifications before its intended release alongside the Future Home Standard in 2025. Professional feedback will help to shape it to align with the UK’s sustainability goals.


The transition to HEM signifies a major step forward in sustainable building practices. Professionals will be equipped with a more accurate, detailed, and flexible tool for energy assessment, supporting the UK’s commitment to sustainability.

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