Shower manufacturer Triton Showers says current assessment methods focus too heavily on heating efficiency, rather than reducing water consumption.
Triton Showers is calling for domestic hot water demand reduction to be given greater recognition in the Standard Assessment Procedure (SAP), arguing that current calculations could allow new homes to meet energy targets without sufficiently reducing water consumption.
In its report, *Recognising Domestic Hot Water Demand Reduction in SAP 10.3, the manufacturer warns that hot water could account for more than half of household energy demand in homes built to the Future Homes Standard (FHS), compared with 35% previously, as improved insulation reduces the energy required for space heating.
The report states that showers and baths account for 55% of domestic hot water demand, but claims current SAP 10.3 calculations allow developers to meet FHS targets through technologies such as heat pumps, solar panels and batteries without necessarily reducing underlying hot water consumption.
Paul Ravnbo-West, market development manager at Triton, said: “The Future Homes Standard is a hugely important step forward for the industry, and we fully support its ambition to deliver lower-carbon homes. Yet there is a growing risk that we’re focusing too much on how efficiently hot water is heated and not enough on how much hot water homes actually need in the first place.
“If we are serious about reducing bills and improving resource efficiency, we need compliance frameworks that recognise technologies capable of eliminating demand at source, rather than simply producing hot water more efficiently.”
The research also highlights the cost of water supply and wastewater disposal, which are not included in SAP’s energy assessment calculations. Triton argues that this limits the assessment’s ability to reflect the full running costs associated with different water technologies.
“SAP is primarily an energy assessment tool and does not account for the financial cost of mains water supply or wastewater disposal. This omission is becoming increasingly significant as water bills rise. In some cases, it can even represent as much as, or more than, the energy cost of providing a shower.
“By overlooking these costs, SAP does not provide homeowners with a complete picture of the potential running costs associated with different water technologies. Greater recognition of hot water demand alongside energy demand would provide a more holistic assessment of household resource use and running costs,” Ravnbo-West said.
As part of the study, Triton compared a conventional mixer shower supplied by a heat pump and hot water cylinder with a high-efficiency shower system designed to work with wastewater heat recovery technology.
The latter reduced annual shower-related energy use from 649kWh to 421kWh, water consumption from 43,796 litres to 25,566 litres and carbon emissions from 109kgCO2e to 69kgCO2e. Combined annual water and energy costs fell from £357 to £220.
The study also found that a typical mixer shower operating at SAP’s minimum recognised flow rate uses around 60 litres of water during a seven-and-a-half-minute shower, compared with 35 litres for the high-efficiency system.
Triton has identified opportunities for SAP 10.3 and the future Home Energy Model (HEM) to better account for technologies that reduce domestic hot water demand, water consumption and wastewater volumes.
Ravnbo-West said: “Stronger alignment between energy- and water-efficiency regulations could also support housing delivery in water-stressed areas, where pressure on resources can affect the viability of new developments.
“The Home Builders Federation estimates that the proposed regulations could add around £3,100 to the cost of delivering a new home. Yet housebuilders specifying demand-reduction technologies, such as electric showers paired with wastewater heat recovery systems, can unlock water company incentives up to £3,500 per plot to encourage delivering water-efficient properties.”