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Last updated: 13th August, 2023


Are Heat Only Boilers Still Used?

Are Heat Only Boilers Still Used?

Key takeaways

  • Heat only boilers are still in use, especially in larger properties with high hot water demand.
  • They operate on open vented or sealed heating systems and use gravity to create water pressure.
  • Compatibility with older systems and high-demand usage contribute to the continued usage of heat only boilers.

Despite technological advancements, heat-only boilers remain a prevalent choice for many homeowners due to their reliability and efficiency. Our blog explores the enduring relevance of these boilers and the key factors to consider when opting for a new boiler installation.

Are Heat Only Boilers Still Used?

Heat-only boilers, known as regular, conventional, or open vent boilers, are a traditional central heating system with a separate hot water cylinder and two tanks. 

They are particularly common in larger properties requiring a higher hot water demand.

Despite the emergence of newer boiler technologies, heat-only boilers remain widely used due to their compatibility with older systems and ability to manage high demand.

However, if you think your property is more suited to a combi, check out our handy guide to the best combis of 2023 right here!

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These boilers operate on an open-vented or sealed heating system, using gravity to produce water pressure. They require an expansion vessel to control the expansion of water as it heats up, protecting the pipes and pumps in the process.

The principal advantage of heat-only boilers is their ability to supply hot water to multiple outlets simultaneously, making them suitable for larger homes or businesses.

What Are Heat Only Boilers? 

Heat-only boilers, also known as regular or conventional boilers, are a type of boiler that utilises a cold water tank, a hot water cylinder, and a feed and expansion tank to heat a home.

They are typically found in larger homes because they are better equipped to supply hot water to multiple radiators, taps, and showers simultaneously.

These boilers draw cold water from the loft-based cold water tank, which feeds to the hot water tank. The water is stored here until you turn on a shower or hot water tap. The feed and expansion tank brings additional cold water into the boiler, ensuring a consistent flow of water for the heating system.


Heat-only boilers can cater to homes with multiple bathrooms or a high demand for hot water. They can supply large amounts of hot water to various needs simultaneously. Furthermore, they are ideal for homes with lower mains water pressure, as the water pressure is generated by gravity from the tanks in the loft.

Heat-only boilers' compatibility with solar power is another advantage. They can harness solar energy to heat water, reducing energy usage and potential savings on utility bills.

However, it is essential to mention that heat-only boilers require separated hot, cold, and feed and expansion tanks, unlike compact combi boilers that do not need additional cylinders.

In summary, heat-only boilers still serve a purpose in homes that require a large volume of hot water for various needs.

Although they lack the compactness of combi boilers, their ability to supply hot water to multiple users simultaneously and compatibility with low water pressure homes makes them a viable option for certain properties.

The Mechanism of Heat Only Boilers

Heat only boilers, also known as regular or conventional boilers, are still utilised in some homes and commercial spaces due to their ability to supply hot water to multiple radiators, taps, and showers simultaneously.

These boilers primarily operate using a cold water tank, a hot water cylinder, and a feed and expansion tank, which makes them particularly suitable for larger properties.

The central component of a heat only boiler is the heat exchanger, where heat is transferred from the heated gas to the water. As the water circulates within the heating system, it is warmed up by the heat exchanger before being directed to the radiators and the hot water cylinder.

The pump plays a crucial role in facilitating hot water circulation through the system, ensuring the consistent delivery of heat to various areas of the property.

In a heat only boiler system, the cold water tank and feed and expansion tank are typically located in the roof space. The cold water tank stores water from the mains supply, while the feed and expansion tank accommodates water volume fluctuations as it heats up or cools down.

This arrangement makes heat only boilers particularly well-suited for locations with lower water pressure, as the cistern can maintain a stable flow to the boiler.

The hot water cylinder is an essential part of the system, usually situated in an airing cupboard, responsible for keeping the hot water ready for use in taps and showers.

As hot water from the heat exchanger enters the cylinder, it displaces the colder water, which is then recirculated back into the boiler for reheating. This continuous heating cycle ensures a steady supply of hot water throughout the property.

The pipework connecting various components of the heat only boiler system plays a crucial role in the efficiency and performance of the heating system.

Proper design, installation, and maintenance of pipework not only contribute to the boiler's longevity but also help prevent heat losses and ensure adequate hot water distribution.

In summary, heat only boilers are a dependable heating solution for larger homes, with their ability to produce and distribute hot water simultaneously to multiple outlets.

The system's key components, including the cold water tank, feed and expansion tank, hot water cylinder, heat exchanger, pump, and pipework, work together to create an efficient and reliable heating system for the property.

Pros of Using Heat Only Boilers

Heat only boilers, also known as regular or conventional boilers, are still popular for many households, especially those with older radiator systems and multiple bathrooms.

Despite the rise of more modern alternatives like combi and system boilers, heat only boilers offer several advantages that make them an attractive option for homeowners.

One of the main benefits of heat-only boilers is their ability to provide central heating effectively for larger homes. They are often better suited for properties with multiple radiators, taps, and showers that require hot water simultaneously.


This is possible because the boiler works in tandem with a hot water cylinder, which stores the hot water until it is needed. Thus, households with multiple bathrooms or frequent users can benefit from a heat only boiler without experiencing a drop in water pressure or temperature.

In addition to their capacity for supplying hot water to multiple outlets, heat only boilers can also be more compatible with older radiator systems. If a property has an ageing radiator network, a heat only boiler may be better suited for maintaining a stable and efficient central heating system.

This is because these boilers can easily adapt to variations in water pressure and flow, helping to maintain consistent performance across the entire network.

From a budget perspective, heat only boilers can be a cost-effective option. Installation costs tend to be lower than that of combi or system boilers, as heat only boilers are less complicated to install and can usually be connected to existing water storage tanks and pipework.

Furthermore, maintenance costs are lower as fewer components are involved in a heat only boiler setup, which can lead to fewer potential points of failure and repair.

Finally, heat only boilers can have a positive environmental impact by offering the possibility of harnessing solar energy for water heating.

By using solar panels paired with a compatible heat only boiler, homeowners can reduce their overall energy consumption, potentially leading to savings on utility bills and a reduction in carbon footprint.

In summary, heat only boilers remain a viable choice for certain households, particularly those with multiple bathrooms, older radiator systems, or budget constraints.

Their capability to provide consistent central heating, compatibility with existing systems, and potential for solar integration make them an option worth considering.

Cons of Using Heat Only Boilers

Heat only boilers, also known as conventional or regular boilers, have been in use for a long time.

However, they come with certain drawbacks that make them less appealing in today's energy-conscious world. In this section, we will discuss the disadvantages associated with heat only boilers.

One notable drawback of heat only boilers is their inefficiency compared to other modern boiler systems. Since these boilers only provide central heating and require a separate hot water cylinder to store hot water, they often use more energy to maintain the water temperature.

This inefficiency can significantly impact energy bills and may contribute to a larger carbon footprint.

Another con of using a heat only boiler is the potential for low water pressure. These boilers rely on gravity to supply water from a tank in the loft, which can result in insufficient water pressure for some properties.

In contrast, system boilers and combi boilers obtain water directly from the mains, ensuring more consistent water pressure throughout the household.

The installation process of heat only boilers can be more complex and costly. As they require a hot water cylinder and a cold water storage tank, installing or replacing a heat only boiler might necessitate additional plumbing work, such as adjusting the pipework or expanding the storage capacity.

Consequently, the installation cost is generally higher than that of combination boilers.


Flue systems for heat only boilers may present challenges in certain properties. The flue must be safely routed outside the property, which could be difficult for homes with limited exterior access or those without a chimney.

The flue system requires regular maintenance to ensure optimal performance and prevent hazardous situations, such as carbon monoxide leaks.

In conclusion, while heat only boilers are still in use, their numerous disadvantages—including lower efficiency and more complex installation compared to contemporary systems—make them a less attractive option for many homeowners.

As energy-efficient and eco-friendly heating solutions continue to gain prominence, property owners need to consider alternatives that suit their needs and preferences.

Heat Only Boilers Vs Other Boiler Types (combi and system)

Heat only boilers, also known as regular or conventional boilers, are still used today mainly for their simplicity and effectiveness in keeping a room heated for longer periods. They solely produce heat and do not provide hot water, which is different from combi and system boilers.

Combi boilers are an efficient and compact option that generates both heating and hot water from a single wall-hung unit. They are connected to the mains cold water supply and can heat water on demand, eliminating the need for a separate hot water tank. Combi boilers are best suited for small flats or homes with low hot water demands, such as one bathroom.


System boilers, on the other hand, are commonly found in modern homes with unvented hot water cylinders, although they can also work with vented cylinders.

These boilers provide both heating and hot water to the property but store the hot water in a separate cylinder, making them an ideal choice for larger homes with a higher hot water requirement.

The primary difference between heat only boilers and combi boilers lies in their function. While heat only boilers only generate heat and require a separate system for hot water, combi boilers provide both heating and hot water through a single unit.

System boilers share some similarities with heat only boilers, as they also need a separate hot water storage cylinder, although they offer a more consistent supply of hot water for larger homes.

In terms of energy efficiency, combi and system boilers generally outperform heat only boilers due to their more advanced technology, though the specific model and installation can affect performance.

A heat only boiler might be more suitable for older properties with existing radiator and hot water systems, whereas a combi or system boiler could be more suited to modern homes with updated plumbing and insulation.

Ultimately, the choice between a heat only boiler, a combi boiler, or a system boiler depends on factors such as the size of the property, the hot water demand, and the current plumbing and heating systems.

Each boiler type has its own advantages and drawbacks, so it's crucial to assess which option best meets the needs of a specific situation.

Ideal Places For Installation of Heat Only Boilers

Heat only boilers, also known as regular or conventional boilers, are commonly used in larger properties with multiple bedrooms and a higher demand for hot water. They are often ideal for homes with older radiators and hot water systems. In this section, we'll discuss the ideal places to install these efficient heating solutions.

Firstly, heat only boilers require a loft for two water tanks: the cold water tank and the feed and expansion tank. The cold water tank supplies water to the hot water cylinder, which stores hot water until needed by multiple taps or showerheads. The feed and expansion tank brings in cold water to the boiler for heating. This space requirement makes properties with lofts suitable for heat only boiler installations.

Moreover, these boilers are a great choice for larger homes with multiple bedrooms and bathrooms. The capacity to cater to high hot water demand across numerous fixtures makes them a fitting option. Additionally, heat only boilers can provide steady central heating whilst meeting simultaneous hot water needs.

In many instances, older properties with pipework and radiators designed for traditional heating systems can also benefit from heat only boilers. As they can easily adapt to existing infrastructure, the need for extensive modifications or upgrades is minimal.

In summary, ideal places for the installation of heat only boilers include properties with available loft space, multiple bedrooms and bathrooms, and older heating systems. These factors, coupled with the reliable performance and the ability to meet high hot water demands, make heat only boilers a practical solution for various households.

Understanding the Output of Heat Only Boilers

Heat only boilers, also known as conventional, traditional, open vent, or regular boilers, continue to be used in certain circumstances.

They are most commonly found in larger households where the demand for hot water from multiple taps, radiators, and showers is higher compared to smaller properties. The output of heat only boilers is essential to consider because it directly impacts their function and efficiency.

When discussing output, we must take into account the tanks involved in these systems. Heat only boilers use a cold water tank, a hot water cylinder, and a feed and expansion tank. These tanks play a significant role in determining the maximum output of the boiler.

The cold water tank stores and supplies cold water, while the hot water cylinder stores heated water for use when needed. Lastly, the feed and expansion tank accommodates changes in the volume of water due to temperature fluctuations.

The output of a heat only boiler system can be further influenced by other factors such as sizing and maximum outputs. It is crucial to ensure that the boiler is sized correctly for the property it serves, taking into account the number of radiators and hot water demand points.

Having a correctly sized boiler will ensure that the system operates efficiently and provides an adequate supply of hot water.

Heat pumps are an alternative to heat only boilers in certain situations, and they come in two varieties: ground source heat pumps and air source heat pumps. Ground source heat pumps utilise the stable, consistent temperature of the ground, while air source heat pumps extract heat from the surrounding air.


Both types of pumps serve effectively in heating systems, but they have different output capacities and efficiencies. Thus, choosing between a heat only boiler and a heat pump depends on factors such as the property size, insulation, and energy efficiency targets.

In conclusion, heat only boilers are still used in cases where multiple hot water demand points need simultaneous access to hot water. The output of these boilers is influenced by the tanks involved, sizing, and maximum output capacities. Other heating solutions such as ground source and air source heat pumps offer alternative solutions, but the selection ultimately depends on the specific requirements of the property and its occupants.

Price and Installation Costs

When considering a heat-only boiler as a possible option for your home, it's important to factor in the costs associated with purchasing and installing this system. Heat-only boilers can still be a viable choice for many households, but their prices and associated installation costs may differ from those of combi or system boilers.

In general, the average price for a new heat-only boiler ranges from £600 to £2,500, depending on the brand, model, and energy efficiency rating. While the initial cost of the boiler itself might be comparable to other types, it's the installation costs that can truly vary. Installing a heat-only boiler can be more complicated than a combi or system boiler, as it requires additional components, such as a hot water cylinder, cold water storage tank, and an expansion vessel.

Installation costs for a heat-only boiler setup tend to range from £1,500 to £3,500. These costs are influenced by factors such as the complexity of the installation, the availability of parts, and even your location within the UK. For instance, living in a remote area might require additional travel expenses for the installation crew, thereby increasing the overall installation cost.

If you plan to replace your old boiler with a heat-only boiler, bear in mind that your existing system may already have the necessary components in place, potentially reducing the cost of installation. However, the cost of replacing your boiler will still depend on factors like the age and condition of your current setup.

In summary, if you're considering a heat-only boiler for your home, it's essential to research prices and installation costs so you can make an informed decision. When comparing boiler costs and installation fees, ensure that you also take the various factors affecting these prices into account, such as energy efficiency, boiler type, and location.

Check out our mega guide on New Boiler Costs!

Brand Comparison of Heat Only Boilers

When discussing heat only boilers, several popular brands come to mind, such as Worcester Bosch, Baxi, and more. A comparison of these brands can help potential buyers make informed decisions.

Worcester Bosch is a well-known brand that offers efficiency and reliability with their heat only boilers. Their products are designed to work with solar power, reducing energy usage and potentially saving on utility bills. The efficiency of Worcester Bosch boilers is guaranteed to be 94%, making them a strong contender in the market.

In contrast, Baxi is another reputable brand that provides heat only boilers for those with limited space. The Baxi Solo 12 HE is an example of a more compact, wall-mounted heat only boiler. With output options ranging from 12kW to 32kW and prices between £500 and £600, this boiler meets the needs of smaller homes.

Comparing boiler reviews is essential to gain an accurate understanding of how these brands perform in real-world situations. Worcester Bosch consistently receives positive reviews for their boilers' performance, efficiency, and ease of installation. On the other hand, Baxi has also gained commendation for their affordability, compact design, and user-friendly controls.

Other brands worth mentioning include Vaillant, Alpha, Viessmann, and Ideal. Each of these brands offers unique features and benefits to suit different consumer needs. For example, Vaillant is known for their eco-friendly products, while Viessmann offers a variety of sizes and outputs to accommodate various homes.

When comparing heat only boilers, it is vital to consider factors such as output, efficiency, and price. Furthermore, it's essential to consult user reviews to gain a comprehensive understanding of real-world experiences. By carefully evaluating these aspects, one can make an educated decision about which brand best fulfils their requirements.

Environmental Impact of Heat Only Boilers

Heat only boilers, also known as conventional or regular boilers, have been widely used for providing central heating to homes. In recent years, however, there has been a growing concern about their environmental impact due to factors such as energy efficiency, carbon emissions, and reliance on fossil fuels.

Energy efficiency plays a vital role in reducing carbon emissions and lowering the overall carbon footprint of a household. Unfortunately, heat only boilers are known to be less energy-efficient than their modern counterparts, such as condensing boilers. The condensing mode in newer boilers enables them to extract more heat from the combustion process, thus reducing waste and carbon emissions.

The majority of heat only boilers are gas boilers, which contribute to greenhouse gas emissions due to their reliance on natural gas. These emissions not only have a negative impact on the environment but also compromise the UK's ambitious climate change goals, including reaching net-zero carbon emissions by 2050.

In recent years, the UK has made significant progress towards incorporating renewable sources of energy into its electricity mix. With a growing emphasis on clean energy, there's a clear trend towards replacing traditional gas boilers with more eco-friendly alternatives. For instance, the International Energy Agency (IEA) has recommended a ban on the sale of new fossil-fuel boilers from 2025 in order to achieve global net-zero emissions by the mid-century.

It's essential to consider the carbon footprint of heating options in every household. Hybrid heat pump systems, for example, can offer a more sustainable alternative to heat only boilers, potentially reducing greenhouse gas emissions by up to 45%. This reduction is mainly due to their ability to use electricity generated from renewable sources, unlike heat only boilers that rely solely on natural gas.

In conclusion, the environmental impact of heat only boilers is an important factor to consider when assessing heating options. As renewable sources of energy become more widespread and energy-efficient alternatives emerge, the demand for heat only boilers may continue to decline. This transition will be crucial in reducing carbon emissions and mitigating the effects of climate change.

Compatibility With Older Systems

Heat only boilers, also known as conventional or regular boilers, are still a popular choice for many homeowners with older central heating systems. Unlike combi boilers, heat only boilers work in conjunction with a separate hot water cylinder and utilise an open vented system. This means they have a cold water tank and an expansion vessel, which provide a more suitable setup for older homes that may not be able to handle the high water pressure from other types of boilers, such as system boilers.

One of the main advantages of using a heat only boiler in an older system is its compatibility with outdated pipework and radiators. As the central heating system in these homes might not have been designed for high-pressure operations, installing a heat only boiler can prevent leaks and damage to the existing infrastructure. Furthermore, heat only boilers can provide a steady flow of hot water to multiple outlets at the same time, which might be preferable in larger homes or multi-storey buildings.

However, it is essential to consider that heat only boilers might be less energy efficient compared to modern boilers, and this can lead to increased energy bills over time. Nevertheless, the compatibility with older systems can outweigh the efficiency drawbacks, particularly if the alternative would be a costly complete overhaul of the central heating system.

In summary, heat only boilers remain a viable option for homeowners with older central heating systems due to their compatibility with open vented setups, existing pipework, and radiators. While they may not be as energy efficient as modern alternatives, the advantages of using a heat only boiler in an older system can make them a practical choice for specific situations.

High Demand Usage of Heat Only Boilers

Heat only boilers, also known as regular, conventional, or open vent boilers, remain a popular option for larger households with multiple bathrooms and a high demand for hot water. These boilers are known for their ability to meet varying hot water requirements, ensuring a steady supply during peak times when multiple hot water taps are in use.

One of the key benefits of heat only boilers in larger households is their ability to maintain high water pressure. This is crucial for situations where multiple showers are simultaneously operating, or when hot water is needed at several points throughout the property. The hot water storage cylinder in a heat only boiler system plays a pivotal role in catering to these high demands, as it stores a sufficient volume of hot water to ensure a continuous supply to all outlets.

In addition to their high water pressure capabilities, heat only boilers are often a good option for properties that require substantial amounts of hot water. These systems can also cater to various hot water usage patterns, thanks to the inclusion of a timer. This allows homeowners to schedule when the boiler heats the water, making the system highly adaptable to the specific needs of the household.

To summarise, heat only boilers are still widely used in larger households with multiple bathrooms and a high demand for hot water, due in part to their ability to maintain high water pressure. These systems are also well-suited to different hot water usage patterns and peak times, thanks to their hot water storage cylinder and timer. In such cases, opting for a heat only boiler can indeed be a wise choice for households seeking a reliable and efficient heating solution.

Future of Heat Only Boilers

Heat only boilers, also known as regular or conventional boilers, have been an essential part of many homes for decades. However, the shift towards more energy-efficient and environmentally friendly heating solutions raises the question of their future use. This section will discuss the future of heat only boilers, their comparison to electric boilers, and the consideration of alternative heating options such as heat pumps.

Heat pumps are another noteworthy alternative. They harness natural heat from the ground or air and can provide both heating and hot water. As a renewable source of energy with lower running costs, heat pumps become increasingly attractive for environmentally conscious homeowners. However, installation can be more expensive than traditional boilers, and heat pumps require sufficient outdoor space to function effectively.

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Frequently Asked Questions

  • What does "heat only" mean on a boiler?

    Heat only boilers, also known as regular boilers, are exclusively designed for heating and distribution of hot water in traditional central heating systems. They work independently of a hot water storage cylinder, usually located in the airing cupboard, to provide hot water throughout the home when needed.

  • What are the disadvantages of a heat only boiler?

    Heat only boilers have some disadvantages, including:
    - Larger space requirements, as they need a separate hot water cylinder and often a cold water storage tank.
    - The hot water supply can run out, requiring time to reheat.
    - They are generally less efficient than combi boilers due to heat loss from the hot water cylinder.
    - Can be more complex to install, especially in homes without an existing traditional heating system.

  • What is the best heat only boiler?

    The best heat only boiler for you depends on your home's specific requirements and your budget. Some reliable brands that produce high-quality heat only boilers include Viessmann, Baxi, and Worcester Bosch. It is important to compare efficiency ratings, warranties, and customer reviews before making a decision.

  • What is a heat only boiler?

    A heat only boiler is a type of boiler designed for homes with traditional central heating and hot water systems. They work by heating water from a separate storage cylinder, which then supplies hot water to different parts of the home as needed.

  • What are the advantages of heat only boilers?

    Some of the advantages of heat only boilers include:
    - Compatibility with traditional heating systems.
    - The ability to replace existing heat-only boilers with minimal disruption and pipework changes.
    - Providing a steady flow rate of hot water to several taps at once, depending on the size of the storage cylinder.

  • How do heat only boilers differ from combi boilers?

    Combi boilers provide both central heating and instant hot water without the need for a separate storage cylinder, while heat only boilers heat water and store it in a separate cylinder for later use. Combi boilers are more compact, energy-efficient, and don't require a separate hot water storage unit. Heat only boilers, however, can supply multiple taps simultaneously and work well with traditional heating systems.

  • Can heat only boilers be upgraded to a pressurised system?

    Yes, heat only boilers can be upgraded to a pressurised system by installing a pressurised hot water storage cylinder such as an unvented or thermal store cylinder. This helps improve the flow rate of hot water throughout the home and eliminates the need for a separate cold water storage tank.

  • Which brands offer reliable heat only boilers?

    When looking for a reliable heat only boiler, consider reputable brands such as Viessmann, Baxi, and Worcester Bosch. Additionally, do research on the specific models, efficiency ratings, and warranties before making a decision. It's also helpful to read customer reviews and get professional advice for a tailored recommendation.

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Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.