Using Waste Water Heat Recovery to save energy

Approximately 85% of the heat energy delivered to showerheads is lost as waste water, equating to 10-20% of a home’s energy output. Existing buildings can reduce their carbon footprint using Waste Water Heat Recovery (WWHR), particularly when it comes to showers.

“Waste Water Heat Recovery for Showers (WWHRS) is a simple heat exchanger technology, designed to recover heat energy from shower drain water and use this recycled energy to pre-heat the incoming cold water that feeds the shower mixer and/or the water heater, cylinder or boiler,” says Dr Ellis Maginn, business development manager at Recoup.

Most WWHRS installed in UK new-build homes is designed to preheat the water supplying both the shower mixer and the hot water source, so as to maximise the energy savings by up to 55%.

Retrofitting

The good news for homeowners and installers is that this technology can be retrofitted. A leading group of independent energy-industry professionals suggested that if WWHRS was retrofitted to just half of existing UK homes, it could result in annual energy savings of 7.79 TWh. That’s potentially more energy saved per year than upgrades to heating controls, loft insulation, and LED lighting combined. .

“For the average home owner, WWHRS can save anywhere from £52 (gas) to £204 (electric) per year in hot water costs and typically offers payback in between two and 10 years,” says Maginn. “WWHRS can be ideal for retrofit, with stand-alone WWHRS systems designed to locate under a standard bath, or vertical systems that can be installed as part of a whole-house upgrade scheme. There is no increased legionella risk if the unit is installed according to the instructions.”

Cost

There are different WWHRS products available for different applications, with the process starting around the £370 mark for domestic systems, it’s a very accessible technology.

“Most energy saving measures focus on space heating efficiency via insulation and airtightness, yet showering equates to around 50-80% of hot water use,” explains Maggin. “WWHRS can reduce the energy demand for showering by 30-55% depending on product type and installation method. As WWHRS is a demand reduction technology, it can be thought of as insulation against hot water loss and part of the building infrastructure. It has an incredibly long serviceable lifetime in the region of 40 to 60 years and requires no planned maintenance.”

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