Triton Showers report highlights SAP shortcomings

Standard Assessment Procedure (SAP) methodology may undervalue technologies that reduce hot water demand at the source, according to a new report from Tritton Showers.

The new report, Recognising Domestic Hot Water Demand-Reduction in SAP 10.3, explores how the SAP 10.3 methodology treats domestic hot water (DHW), which is expected to represent a significantly larger proportion of regulated household energy use as space heating demand falls in highly efficient, low-heat-loss homes constructed under the Future Homes Standard.

The Report claims the current SAP 10.3 approach appears to place greater emphasis on central heating system efficiency, fabric performance and photovoltaic (PV) provision than on reducing DHW demand at source, suggesting this risks encouraging homes that are compliant on paper but not fully optimised for hot water demand, water consumption and long-term system efficiency.

The manufacturer has identified seven practical policy levers that could help SAP 10.3, the Home Energy Model (HEM), and future home-energy frameworks better recognise domestic hot water demand reduction.

Recommendations include introducing a dedicated domestic hot water demand-reduction metric so that compliance rewards homes for requiring less hot water, as well as closer alignment between SAP 10.3, HEM and Part G to recognise the combined water, energy, cost and carbon benefits of demand-reduction technologies. The report notes that SAP 10.3 currently excludes the costs and operational emissions associated with mains water supply and wastewater treatment.

Paul Ravnbo-West, market development manager at Triton Showers, commented: “Point-of-use demand-reduction technologies like high-efficiency electric showers paired with WWHRS are exactly the type of practical, scalable innovation that should be encouraged under the Future Homes Standard.

“Our recommendations are intended to help policymakers ensure new homes are designed not only to generate heat efficiently, but also to use less hot water in the first place. This approach could help lower household bills, reduce pressure on water resources and provide more flexible compliance pathways for developers, particularly in hard-to-treat properties.”