With stringent regulations reshaping how heating, hot water and plumbing systems must operate, existing and new-build homes are increasingly being designed or retrofitted to increase efficiency and lower carbon output. Greg Banham, Commercial Director for Navien UK, says that while most focus remains on insulation and heating system performance, hot water efficiency remains a priority.
By focusing on insulation and heating systems, the industry has made significant progress in improving the energy efficiency of UK homes. However, this progress is also highlighting an area that has often been overlooked. As space heating demand continues to fall, domestic hot water (DHW) is becoming an increasingly important part of both energy use and carbon emissions.
Often treated as a background consideration in system design, it accounts for a growing share of overall energy use and associated emissions. And as buildings become better insulated and require less energy for space heating, demand for domestic hot water is becoming more visible.
The changing balance of energy use
Home heating has always been at the forefront when the topic of energy use is raised. Whether it’s improving insulation, installing double-glazing windows or upgrading to modern hot water systems, enhancing performance and reducing carbon emissions always come back as the main improvements needed for homes.
Even though modern homes are built to keep heat in, the energy used for space heating is decreasing due to improved insulation and more efficient heating systems. As the demand declines, domestic hot water is taking a larger share of household energy use and, while homeowners continue to expect reliable hot water for showers and everyday activities, this change in demand is shifting the balance of energy consumption within homes.
According to the Hot Water Association, water heating already accounts for 20 to 25% of annual domestic gas use and contributes four to five percent of the UK’s total carbon emissions. As overall building space heating demand continues to fall, those proportions will rise further.
This changes how the industry thinks about performance. The future of efficiency will depend not only on reducing heat loss but also on improving how hot water is stored and managed.
Changing expectations are influencing system design
There is a growing expectation that heating systems should deliver consistent comfort while offering better control over energy use. Smart controls and connected systems are making energy consumption more visible, influencing how people think about efficiency and running costs.
It’s not just about delivering heat reliably. It’s about designing systems that balance comfort and flexibility across both space heating and hot water. This places greater importance on system design, controls, and storage, and on how individual parts can work together to run smoothly as one system.
The growing importance of reliable DHW is also reinforcing the need to think more carefully about complete system performance. For HVAC installers, that means looking beyond individual products and taking a whole-system approach, taking into consideration where future-ready solutions could be used to improve efficiency, performance and comfort.
The untapped energy in homes
The UK has around nine million hot water cylinders installed in homes, traditionally viewed as storage, but they are now recognised as a form of energy storage. These systems can store energy when demand is low, then release it later when needed. They behave like thermal batteries operating at the household level.
As the electricity system continues to decarbonise and rely heavily on renewables, this kind of flexibility becomes more valuable. It allows energy to be used more efficiently, reduces strain on the grid at peak times, and helps households take better advantage of lower-carbon electricity. Heat pumps are just one example of the renewable and low-carbon solutions growing in popularity on the market. By moving existing heat rather than creating it, they transfer energy from outside air to indoors, creating more energy than they consume for enhanced efficiency. Heat pumps such as Navien’s PEM750 monoblock air source heat pump have a high-efficiency rating, and users can rely on the heat pump to provide them with consistent heating and hot water while reducing their homes’ carbon footprint and energy bills.
“As homes become more efficient, DHW will play a key role in delivering flexibility and lower-carbon performance.” – Greg Banham, Navien UK
A growing part of future housing performance
Technologies like heat pumps rely heavily on well-designed hot water systems to perform efficiently. As these systems become more common, the relationship between heat generation, storage, and demand will become increasingly important for installers and specifiers.
Policy direction, such as the anticipated Future Homes Standard, is pushing the industry towards a more integrated view of building performance. Success will depend not only on reducing heat loss but on improving how energy is used across the entire home. This creates a clear opportunity to improve performance through better system design, smarter controls, and complete system thinking.
At Navien UK, this opportunity is central to how the future of heating is being viewed. As homes become more efficient, DHW will play a key role in delivering flexibility and lower-carbon performance. The industry has long focused on how homes are heated; however, the question is increasingly about how well they manage the energy they already use every day.
