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HEM, the replacement for SAP, is intended to have more functionality that enables its use in a greater number of applications. In contrast, SAP is primarily used for EPC production using a significant number of standardised inputs. It does this through a move to half-hourly calculations (from monthly) and allowing variation of more inputs values.

There are a number of potential implications of this:

  • Need for upskilling of SAP assessors (especially for existing home assessments)
  • Potential increased costs for delivering assessments
  • Potential overlap with dynamic modelling for overheating purposes – will it be possible to avoid dynamic modelling in some circumstances?
  • Supposed quicker inclusion of new technologies

Moving to half-hourly calculations also provides the potential for benefit to be obtained from smart appliances, batteries, thermal storage and other load shifting methods. However, there appears to be a missed opportunity here, as carbon factors seem to be fixed rather than varying on a daily and seasonal basis.