How installers can maximise hot water delivery without a cylinder

As UK homes continue to evolve, so do your customers’ expectations for comfort, efficiency and convenience – especially when it comes to hot water. In this article, Graham Parkes, Commercial Director at Navien UK, explores how installers can meet rising hot water demands in modern homes – and why next-generation combis may be the key.

Long gone are the days of waiting endlessly for the shower to heat up or scheduling baths like a military operation.

Today, the modern home is built for comfort, with families expecting instant, reliable hot water delivery that keeps pace with their varying lifestyles.

And let’s face it, whether it’s a bustling morning rush, a luxurious soak in the tub after a long day, or simply the joy of a powerful shower, hot water is a necessity to us all.

With the boiler often seen as the beating heart of the home, its role is vital for ensuring hot water delivery throughout the property.

Homeowners generally expect hot water to be delivered instantly, reliably, and safely, but at the same time, they tend to understand the limitations on simultaneous use and temperature. Due to the nature of combi boilers, perceptions of hot water are often shaped by a balance between convenience and these limitations.

But with greater demands come greater challenges. Larger homes with growing families and high-performance appliances require a boiler that is more than ‘good enough’. In fact, homeowners are thinking about energy efficiency, finding new ways they can cut energy waste, improve their ErP rating or enhance their homes with smart technology.

Evolution

Now, it’s no secret that the average modern home uses more hot water than it did a generation ago. The rise of rainfall showers, large bathtubs and smart control systems has made convenience and comfort the norm. At the same time, housing density and floorplans are changing too. Open-plan living spaces, loft conversions and side extensions are placing higher expectations on systems once designed for simpler layouts.

What’s more, customers now expect instant hot water. The days of waiting for a cylinder to reheat, or carefully staggering usage between the kitchen and shower, are fading fast. These expectations are also converging with tighter energy efficiency targets and a push toward lower emissions, all of which are reshaping how hot water systems are specified and installed.

Revolution

Compact and eliminating the need for a cylinder, combi boilers free up valuable space in the home, allowing ample space for a storage cupboard or even a small w/c. They also reduce gas costs by removing the heat losses associated with storing unnecessary hot water in a cylinder.

However, in households with high simultaneous demand, such as when the washing machine is running, hot water is being used in the kitchen, and someone is taking a shower – combi boilers can begin to struggle. Flow rates drop, temperatures fluctuate, and customer satisfaction suffers. Installers have often had to choose between oversizing a boiler (with all the inefficiencies that come with it) or recommending a system boiler with an unvented cylinder, which requires more space and longer installation times.

Fortunately, innovation in boiler design is beginning to close that gap.

Solution

A new generation of combi boilers has emerged over the last few years, engineered specifically for high-demand homes that need excellent hot water performance without the complexity of cylinders. These advanced models integrate larger stainless steel heat exchangers, pre-heat capabilities and – in some cases – built-in thermal stores to deliver strong, stable hot water at flow rates previously thought impossible from a combi.

A leading example of this is Navien’s flagship NCB700 ON, a combi boiler specialised for domestic hot water, with sufficient output capacity to supply a large volume of hot water quickly and instantly. At the same time, it remains compact in size and is equipped with both internal and external recirculation systems.

Designed to provide ample hot water, sufficient to run up to three showers simultaneously, the NCB700 ON matches the performance of some system boilers with a separate cylinder. Unlike a system boiler, it eliminates the need for additional cylinder space and avoids the energy losses associated with storing hot water, making it a more efficient and space-saving choice. It’s an attractive option for larger homes that need more from their combi without moving to a different system entirely.

Alongside the flagship NCB700 ON, the wider NCB ON range has also been developed to provide reliable heating and hot water solutions for different household requirements. With hot water performance placed at the forefront, the range is designed around user comfort and convenience, while still delivering the efficiency and space-saving advantages of a combi boiler.

Conculsion

The domestic hot water landscape is changing fast. With consumer expectations higher than ever and building standards tightening year by year, it’s clear that installers need to look beyond the basic combi when specifying for high-demand homes.

Fortunately, manufacturers are rising to the challenge. Innovations in boiler design are giving professionals the tools to meet demand without compromise.

Whether it’s a growing family, upgrading a property portfolio, or a self-builder looking to minimise system complexity, to meet homeowners’ needs for hot water and their performance expectations, it’s clear that high-performance combis are increasingly the right fit.