It’s vital to pick the right boiler for your central heating and hot water needs. Read on to learn more about the types of boilers available in the UK to ensure you choose the best boiler for your home.

Choosing the right boiler for your home is essential since heating and hot water account for over 50% of what you spend annually on energy bills.

There are different types of boilers, and the one you select can significantly impact your heating and hot water system.

Every home is different, so the right type of boiler for one household may not be suitable for another.

If you’re considering getting a new boiler, knowing the available options and how they work can help you make an informed decision.

This guide explores the different types of boilers for domestic households in the UK, including how they work, their advantages and disadvantages, and how to choose the right boiler for your home.

Quick Takeaways:

• The UK’s most popular types of boilers include combi, system, and conventional boilers.
• Combi boilers provide hot water on demand, eliminating the need for a tank or cylinder.
• System boilers require a hot water cylinder to deliver heating and hot water to your home.
• Heat-only boilers heat your radiators directly, usually including a separate hot water storage cylinder and a cold water storage tank.
• The most appropriate boiler for your home will depend on your hot water demands, property size, the age of your heating system, and available water pressure.

Are you wondering how much a new boiler costs? Check out our guide on options available if you need a new boiler but can’t afford it, as well as boilers on finance and government boiler grants here.

What Are The Different Types of Boilers in the UK?

Even though most boilers perform relatively similar basic operations of burning fuel and transferring heated water to radiators and taps, each boiler type operates differently.

The following sections explain how each boiler type provides warmth and hot water:

Combi Boilers

A combination or combi boiler provides heating and hot water from a single unit and is usually wall-hung.

They’re the most compact option, combining all the components of a traditional central heating system into a single unit.

Combi boilers are highly efficient and don’t require a hot water tank or separate water cylinder.

These types of boilers are very popular with statistics showing that by 2019, over 54% of households in the UK were using combi boilers.

How Do Combi Boilers Work?

Combi boilers connect directly to the main cold water supply and provide hot water on demand, eliminating the need for a tank or cylinder.

They burn fuel like gas or oil and have an integral heat exchanger that gets hot enough to instantaneously heat the cold water from the mains supply as it flows over it.

Combi boilers consume less power and are affordable and efficient to run since you don’t have to heat and store water.

What Are the Advantages of Combi Boilers?

• Space Saving – The compact size of combi boilers makes them ideal for smaller spaces as they don’t require separate water tanks or cylinders.
• Better Aesthetics – Combi boilers easily blend into kitchen cupboards. The boiler casing hides all the components, making it neater and more aesthetically pleasing.
• Easy to Service — Combi boilers are more accessible to service and repair since everything is housed in one unit. Thanks to their popularity, most engineers are also trained to work with combi boilers, so you can easily find a qualified one in your area.
• Instant Water Heating – You don’t have to worry about long wait times for hot water with combi boilers. They produce hot water on demand without waiting for a tank to heat up.
• Energy Efficient — A combi boiler is an excellent choice if you’re looking for a highly efficient boiler. New models have over 90% efficiency and can significantly reduce energy bills.
• Low Installation Costs – Combi boilers are easier and cheaper to install. There’s only one unit to fit, and they don’t require complex pipework.

What Are the Disadvantages of Combi Boilers?

• Limited by Mains Pressure – Combi boilers don’t work well in homes with low water pressure or poor incoming flow rates.
• Not Suitable for High Demand – The flow rate will drop if you open two or more outlets simultaneously, making the boiler less efficient for households with complex water needs.
• Solar Incompatibility – Most combi boilers are incompatible with solar water heating systems.

Is A Combi Boiler Right for You?

A combi boiler can be right for you if you have:

• A small household or flat with limited space
• 10 radiators of fewer
• No loft to put a water tank
• Only one bathroom

Check out our video on how to vet boiler brands/models in the UK:

System Boilers

System boilers, also called sealed or closed vent boilers, require a hot water cylinder to deliver heating and hot water to your home.

They’re an upgraded version of heat-only or conventional boilers. However, heat-only boilers don’t need a cold water tank.

Additionally, components usually external to heat-only boilers, such as valves and pumps, are built into the system boiler’s body.

The average system boiler is still quite economically viable and efficient to run. However, they can be way too expensive in a smaller household where the family members do not require a lot of hot water at any given time.

How Do System Boilers Work?

System boilers are pressurized insulated systems. A filling mechanism draws cold water straight from the main supply, eliminating the need for cold water storage.

This water is heated before being transferred to either the hot-water storage container or the radiators. The hot water is stored in the cylinder until it’s needed.

A built-in expansion vessel in system boilers maintains the right system pressure level, guided by the heating pump. This allows the boiler to handle higher capacities than combi boilers, making it suitable for households with high demands.

System boilers are very versatile and can heat several rooms and operate multiple bathrooms without dropping the temperature of your heating systems.

They’re an excellent solution for homes with several bathrooms. However, system boilers require more maintenance and space for effective installation.

What Are The Advantages of System Boilers?

• Suitable for Larger Homes — The hot water storage cylinder makes system boilers ideal for households with high hot water demands. If you have many bathrooms and showers, they can simultaneously deliver reasonable flow rates to multiple outlets.
• Use Less Space Than A Regular Boiler — System boilers have internalised components and don’t require a cold water tank, meaning they need less space than a regular boiler.
• Quicker Install — System boilers have fewer components to fit, so they’re quicker to install than regular boilers. Fewer components also make the installation location more flexible.
• Zero Components in the Attic – With system boilers, you don’t need to put any components in the attic so you don’t have to worry about any potential freezing or leaks in the winter months.

What Are The Disadvantages of System Boilers?

• Cylinders Need Space — System boilers use cylinders that require adequate space, making them unsuitable for smaller homes. If you’re replacing a combi boiler with a system boiler, you’ll need to find a suitable location for the cylinder.
• No Hot Water on Demand — Water heating can take time, so you’ll need to plan to ensure you have sufficient hot water stored or wait for the water to heat up.
• You Can Run Out of Water — If your household has a high demand over a long period, the cylinder can run out of water and will take time to refill.
• Flow Rate Depends on Mains Pressure – Good hot water flow will depend on the incoming mains water pressure. If the pressure is low, your home will have a limited flow rate.
• Not Suitable for Old Systems — System boilers’ high-pressure nature makes them unsuitable for properties with old systems that have sensory issues.

Heat Only/Conventional Boilers

Heat-only boilers, also called conventional or regular boilers, heat up your radiators directly. The system includes the boiler, a separate hot water storage cylinder, and a cold water storage tank.

Conventional boilers are usually found in older homes. Such properties may not have pipework suitable for higher water pressure and thus may need to continue using a conventional boiler system.

Heat-only boilers usually have components housed externally from the boiler, such as a circulation pump.

How Do Conventional Boilers Work?

A heat exchanger warms water when fuel is ignited, and can use gas or oil. A pump transports the water to a storage tank. This hot water then flows through to radiators to heat them, or into your taps when you switch them on.

A cold-water tank, usually positioned in higher areas of the house, such as the attic or loft, provides cold water to the boiler. Gravity aids in filling the boiler.

The boiler heats water and stores it in a hot water cylinder until it’s needed for radiators or domestic use.

They also have an on/off switch, allowing you to heat water in the storage tank when you know you’ll need it and leave it off when not in use. 

As long as the cylinder contains enough hot water, you should be able to use water from many taps simultaneously.

What Are The Advantages of Conventional Boilers?

• Suitable for Large Households – A conventional boiler can help you meet the demands of a large household. Hot water can run from several taps simultaneously, making it suitable if you have multiple bathrooms where people frequently use hot water.
• Back-Up Water Heating — You can equip the cylinder with an immersion heater to ensure you still have hot water even when your boiler breaks down.
• Suitable for Older Heating Systems – Conventional boilers don’t require water to be supplied at high pressure, making them a good option for older heating systems that may not tolerate the high pressure of a closed system.
• Solar Compatible – Conventional boilers can work with solar water heating systems and help lower your bills while helping you contribute to environmental sustainability.
• Low Replacement Costs — Conventional boilers are the cheapest types to buy, making replacement them less costly.

What Are The Disadvantages of Conventional Boilers

• Less Efficient — Heat-only boilers can be less efficient than combi boilers because some heat is lost from storing water in the cylinder.
• Takes Up Space – You’ll need somewhere roomy to store the boiler’s water tank and cylinder, making the heat-only boiler unsuitable for households with limited space.
• No Hot Water On Demand – Conventional boilers don’t provide hot water on demand, and you may need to wait for the cylinder to heat up and the water to reach the right temperature.
• Complicated Installation — Installing a conventional boiler can be complex due to additional parts, pipework, a cold water tank, and a storage cylinder.

Is A Conventional Boiler Right for You?

A conventional boiler can be right for you if:

• You have a large household
• You have more than one bathroom
• Your home gets a low mains pressure
• You live in an older house

New boiler cost guides:

• System boiler prices UK.
• Hydrogen boiler costs.
• Costs to replace a conventional boiler with a combi boiler.
• Combi boiler prices UK.
• Back boiler removal costs.

How Do You Choose The Right Boiler for Your Home?

Choosing the right type of boiler for any home should be based on the following parameters:

Size of the Property

A boiler is the main heating system for houses hence it is important to choose a boiler that emits enough heat to keep the property warm.

The size of a domestic boiler is determined by its heat generation efficiency, which normally ranges from 5 to 35 kW.

Check out our boiler brand price guides and comparisons:

• British Gas new boiler costs.
• How much is it to fit a new boiler?
• How much does a Vaillant boiler cost?
• Baxi boiler costs.

Water Usage

The usage of water is directly proportional to the number of family members.

A 24-30 kW boiler is ideal for most houses with a single bath and shower.

A larger 30-35 kW boiler may be preferable for an additional en-suite bathroom.

In larger homes where everyone has a separate bathroom, a system boiler that stores hot water in a storage cylinder may be ideal.

In our guide, learn all about the different types of boilers, including condensing boilers, LPG boilers, oil boilers, and Opentherm boilers, and how to calculate boiler size.

Available Space

The space is a good deciding factor for the type of boiler one should invest in.

If the space is tiny, opting for a boiler that does not need a separate hot water storage tank is better.

Types of Boilers Conclusion

The different types of boilers available in the UK include combi, system, and conventional boilers. The most appropriate boiler for your home will depend on various factors, including your hot water demands, property size, the age of your heating system, and available water pressure.  

It’s important to consider the pros and cons of each type of boiler to ensure you make an informed decision. Combi boilers are the most popular type installed in the UK and are suitable for small to medium-sized homes with one or two bathrooms. System or conventional boilers are more appropriate for larger homes with multiple bathrooms.

Sources and References

• https://energysavingtrust.org.uk/advice/boilers/
• https://www.statista.com/statistics/292259/boiler-types-in-dwellings-in-england/