When we talk about decarbonising homes, the conversation nearly always starts with fabric, i.e., insulation, windows, doors, and air-tightness- and all rightly so. “Fabric first” is the foundation, since space heating is nearly always the largest energy user within a home.
But once we have tackled the walls, floors, and roofs, where do we look next for meaningful, affordable carbon savings?
You might be surprised, but the next single biggest energy use lies in the bathroom.
Every day we make hot water, and more often than not, we send it down the drain while it’s still warm. Around 80-85% of a household’s hot water use comes from showering, and most of that energy is sent to the sewers after just 2 seconds’ use. For a family of four using a shower for 30 minutes/day in total, this is equivalent to running the oven, the grill, and four hobs flat out for half an hour every single day.
Luckily, technology exists to stop this massive energy waste. Shower wastewater heat recovery units capture heat from wastewater and utilise it to preheat the incoming cold water supply. That means the boiler or electric shower does not have to work as hard, saving substantial amounts of energy every time the shower runs.
From an energy perspective, the impact is considerable. Depending on the model, these systems can save between 640 and 1,500 kilowatt-hours per year. That is equivalent to several solar PV panels on a typical UK roof, but at a fraction of the cost. Furthermore, unlike solar, the savings are applicable all year round, regardless of weather or daylight conditions.
Electric showers and the fuel poverty challenge
Previously, electric showers were not compatible with heat recovery systems; however, recent advances in electric shower design now enable them to integrate with such systems. The latest unit from Triton Showers can adjust its power usage in real-time, depending on the temperature of the incoming water. When used in conjunction with the Zypho Slim50 horizontal heat recovery unit, this can cut electricity demand from 8.5 kW down to just 5 kW.
Zypho Slim50 Horizontal
For residents, this is more than a technical development. It is a fuel poverty win. A household can save around £165 per year, assuming 30 minutes of shower use per day. If that rises to an hour’s daily use (any teenagers in the house?), the savings double to £330.
These savings repeat every year, with no behavioural change required. Residents get cheaper, better showers. In fact, flow rates of up to 5 litres per minute mean the experience can feel like an upgrade compared with traditional electric showers.
What about installation, maintenance, and SAP?
These were some of the first questions raised in recent discussions across the sector. The answers are encouraging.
- Installation: For a shower over a bath, the heat recovery unit typically sits under the bath and is a morning’s work for a plumber to install. It is a standard plumbing job, with no pumps or electrical aspects involved.
- SAP uplift: The greatest benefits are realised when fabric upgrades have already been addressed. In those homes, shower heat recovery can provide a massive uplift. Whether you are building new or retrofitting existing stock, the SAP / EPC benefit is excellent value for money.
- Maintenance: The units become an integral part of the plumbing. They are passive, self-draining, and designed to last, and have already been installed in thousands of new-build homes for over a decade. There are no tanks or stored water, which means minimal risk of leaks or hygiene issues.
- Suitability for retrofit: Most social housing stock (c. 80%) includes baths with showers overhead, which makes retrofitting straightforward. The twin benefits of decarbonisation and fuel poverty are virtually unbeatable in terms of bang-per-buck.
Policy context and decarbonisation pathways
As the sector works towards achieving EPC C by 2030, and with the Decent Homes consultation indicating a greater emphasis on energy efficiency, technologies like this should be at the forefront. They deliver considerable SAP benefits, align with fuel poverty objectives, and reduce long-term carbon emissions.
A smarter step after “Fabric first”
If we accept that “Fabric first” is non-negotiable, then shower heat recovery is the logical next step, rather than moving to higher-cost renewable energy sources. Pound for pound, it is one of the most cost-effective interventions available today.
The call to action is simple
We need to put an end to wasting energy – and money – and take the next significant step in energy efficiency within homes.
Talk to us
We are keen to work with housing providers and partners to demonstrate the benefits at scale. If you would like to explore a pilot, we can provide the units, support installation, and help model the SAP improvements. Together, we can prove that the bathroom is not just a place of daily routine, but also a place of real carbon and cost savings.
Email shower@zypho.uk or call 01525 647220.
