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Last updated: 18 September 2023

Types of Boilers Explained: Combi, System & Conventional

types of boilers

Boilers are like the brainy wizards of the heating world. They solve the problem of freezing homes by generating hot water or heat, leaving us warm and cosy. And that’s while keeping energy bills under control! If you have decided to buy a boiler but got lost in all the types of boilers out there, you’re in a good place. 

In this article, we’ll dig into the different types of boilers and their features, so you can find the perfect match for your home. However, next, you’ll need boiler quotes from a professional installer to have the boiler types explained and tailored to your situation. 

Yet looking for a trusted expert can cost you the valuable time you could spend with your family instead. Moreover, even after hours or days of browsing and reaching out to installers, you can still have no actionable information at your fingertips.

Thankfully, GreenMatch can reduce your stress. Fill out our 30-second form and, in return, we’ll provide up to 3 quotes from our network of trusted boiler installers. Our service is free, without obligation, and takes less than a minute. Click the link below to get started.

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types of boilers diagram

In the UK, three types of boiler systems run the heating show: combi boilers, system boilers, and conventional boilers.

Combi boilers, or combination boilers, are the most popular with UK homeowners. They are energy-efficient, providing both heating and hot water on demand without the need for a separate storage tank.

System boilers are another favourite, known for their simplicity and ease of installation. They work with a separate hot water cylinder and suit larger households with higher hot water demands.

Conventional boilers come with a hot water cylinder and a cold water storage tank. They are an excellent choice for homes with low water pressure as they can supply substantial amounts of hot water to multiple bathrooms.

Worth noting, that since 2005 all gas types of boiler systems installed in the UK are required by law to be condensing boilers. It’s highly advisable to consult a qualified boiler installer to make sure that your boiler meets all current requirements and regulations.

There are hundreds of types of boilers in the UK and whichever you choose, it’s still a costly investment. Thankfully, the UK government offers boiler grants that can help reduce the initial spending while getting a new boiler for your home. This way, getting a boiler becomes pretty affordable for any homeowner.

These three domestic boiler types have their pros and cons, and choosing the best boiler for your needs and property requirements is vital. Let’s take a closer look at these boiler types.

Combi boilers

A combi boiler, short for combination boiler, is a compact unit that integrates home heating and an on-demand hot water supply. It operates by drawing water directly from the mains and heating it as needed. 

Combi Boiler Lines

When you activate the heating, the combi boiler’s electric ignition uses the fuel – gas, oil, or LPG (liquid petroleum gas) – in a sealed combustion chamber inside the boiler. 

The primary heat exchanger within the boiler is then heated, raising the incoming water’s temperature to around 60℃. This heated water circulates through the radiators, providing warmth to your home.

When you require hot water, such as when you turn on a hot tap or shower, the combi boiler immediately heats the water on demand. It utilises primary and secondary heat exchangers for this purpose.

boiler heat exchangers
  • A primary heat exchanger is responsible for heating water used for central heating. It transfers heat from the combustion process to the water flowing through the central heating system, like radiators or underfloor heating.
  • A secondary plate heat exchanger is dedicated to heating water for domestic use. It transfers heat from the primary heat exchanger to the water flowing through taps or showers, delivering instant hot water.

Combi boilers are highly energy-efficient, with electric combi boilers reaching a whopping 100% efficiency. Their small size, absence of a hot water storage tank, and ability to provide instant hot water make them a top choice among UK homeowners. They are suitable for small to medium-sized homes with lower hot water and heating demands. However, ensure sufficient mains water pressure for optimal performance.

Pros and cons of combi boilers

Advantages
  • Energy efficient
  • Space-saving
  • Instant hot water supply
  • Cost-effective
Disadvantages
  • Limited hot water supply
  • Not suitable for weak water pressure
  • Not suitable for larger properties

Advantages:

  • Energy efficiency. Combi boilers boast remarkable energy efficiency, with some models achieving 100% energy utilisation.
  • Space-saving. Combi boilers are especially suitable for small homes or properties with limited space since they eliminate the need for a hot water storage tank and a cylinder.
  • Instant hot water supply. Combi boilers provide hot water instantly, eliminating the need to wait for a tank to heat up.
  • Cost-effectiveness. Combi boilers serve as a cost-effective heating system, making them an excellent option for homeowners looking to reduce their heating expenses. On top of that, due to its compact size, the cost of moving a boiler of this type won’t cost you a lot.

Disadvantages:

  • Limited hot water supply. Combi boilers may struggle to meet high demands for hot water, particularly in larger homes with multiple bathrooms.
  • Unsuitable for weak mains water pressure. Combi boilers require robust mains water pressure to function effectively, which may render them unsuitable for homes with low water pressure.
  • Unsuitable for larger homes. Combi boilers are only appropriate for small to medium-sized homes.

Think that a combi boiler is what you need? You should consult a professional installer regarding the boiler prices and to help you choose a perfect match. Yet chances are you’ll need to sacrifice your precious free time to find suitable quotes from experienced engineers.   

Fortunately, GreenMatch can save you time. Instead of spending hours researching the best installers for the job, simply complete our 30-second form. Next, we’ll connect you with up to 3 local heating engineers. Then you can compare their prices without having to commit to any orders. Just click the button below to begin.

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Conventional boilers

A conventional boiler, also known as a regular or heat-only boiler, follows a traditional heating system with hot and cold water storage tanks. 

Conventional Boiler Lines

The boiler’s electric ignition utilises the fuel (mains gas, oil, or LPG) heating the primary heat exchanger. This heats the incoming water, providing warmth through the radiators.

For hot water needs, the conventional boiler heats the water in a hot water cylinder located in an airing cupboard. It can supply hot water to multiple outlets simultaneously, making it suitable for larger households.

Conventional boilers require space for the cylinder and cold water tank, and the stored water may lose heat over time, impacting efficiency. Installation can also be more complex and costly due to additional components and pipework.

This is why conventional boilers suit larger households with high hot water demands and areas with low water pressure. They offer simultaneous hot water supply but need space for tanks.

Pros and cons of conventional boilers

Advantages
  • Suitable for low-pressure areas
  • Multiple-outlet hot water delivery
  • Compatible with solar panels
Disadvantages
  • Need more space
  • Delayed water supply
  • Tend to lose heat

Advantages:

  • Suitable for low-pressure areas. Conventional boilers are well-suited for regions with low water pressure, utilising gravity-fed water from loft tanks to create the necessary pressure.
  • Multi-outlet hot water delivery. Conventional boilers can efficiently provide hot water to several bathrooms or outlets simultaneously, making them ideal for larger households.
  • Solar panel compatibility. Conventional boiler systems can be integrated with solar thermal panels, offering more environmentally friendly heating options.

Disadvantages:

  • Space requirements. Conventional boilers occupy a considerable amount of space in a home due to the need for a hot water cylinder and a cold water tank.
  • Delayed hot water supply. Unlike combi boilers, conventional boilers require time to heat up the stored water in the cylinder, resulting in a delay before hot water becomes available.
  • Heat loss. The hot water stored in the cylinder may experience heat loss over time, potentially reducing the overall boiler efficiency.

Consulting with a heating professional can help determine the best boiler brand, type and size for your specific needs. We can save you time googling and offer you more information so you can make the best decision for your home.

If you’re interested in more details about conventional boilers, just fill in the contact form below. We will provide you with up to 3 quotes from our trusted installers. GreenMatch services are free and there is no obligation to accept any of the quotes you receive. 

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System boilers

A system boiler operates similarly to a conventional boiler, but it directly draws cold water from the mains, eliminating the need for water tanks. It produces hot water for a storage cylinder to heat the central heating system. 

System Boiler Lines

When the heating is activated, the system boiler’s electric ignition uses the fuel (mains gas, oil, or LPG) inside the boiler. The primary heat exchanger heats the incoming water which then flows through the radiators, providing heat to your home.

When hot water is needed, the system boiler heats the water in a hot water cylinder. The cylinder is usually concealed in an airing cupboard. 

System boilers draw water directly from the mains and heat it in the cylinder, providing a mains pressure supply to several taps simultaneously, making them suitable for larger families and homes with several bathrooms.

However, they require time to heat up the water in the cylinder, leading to a delay in obtaining hot water. Additionally, their installation can be more complex and costly due to extra components and pipework.

A system boiler is an excellent choice for larger homes with high hot water demands. Moreover, it offers mains pressure hot water and compact size.

Pros and cons of system boilers

Advantages
  • Pressurised hot water supply
  • Suit larger homes
  • Space-efficient
  • Compatible with solar panels
Disadvantages
  • Delayed hot water availability
  • Heat loss
  • Complex and costly installation
  • Unsuitable for weak water pressure

Advantages:

  • Pressurised hot water supply. System boilers utilise water from the mains, heating it in a hot water cylinder to provide a continuous flow of hot water at mains pressure to multiple taps simultaneously.
  • Ideal for larger homes. System boilers are well-suited for spacious residences or homes with numerous water outlets, ensuring sufficient hot water supply throughout the property.
  • Space-saving design. System boilers don’t rely on water tanks in the loft, making them a space-efficient heating option (compared to conventional boilers), especially for homes with limited space.
  • Compatibility with solar panels. System boiler systems can be integrated with solar thermal panels, enabling homeowners to adopt more sustainable and eco-friendly heating alternatives.

Disadvantages:

  • Delayed hot water availability. System boilers require time to heat the water stored in the cylinder, leading to a delay in obtaining hot water at the taps.
  • Heat loss. The stored hot water in the cylinder can experience heat loss over time, potentially reducing the overall energy efficiency of the system.
  • Complex and costly installation. Installing a system boiler system may involve additional components and pipework, leading to increased complexity and higher installation costs compared to other boiler types.
  • Unsuitable for weak mains water pressure. System boilers demand robust mains water pressure to function effectively, making them unsuitable for properties with low water pressure from the mains.

Do you think a system boiler is a perfect fit for your home? We can help you find your best deal! Simply by clicking the button below, you can avoid the hassle of looking for installers. Fill in our quick form and get in touch with up to 3 professional installers. Our service is totally free and non-binding. Just click below to begin. 

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Which boiler type is the best for your UK home?

The best type of boiler for your UK home depends on various factors such as your household size, water pressure, hot water demand, available space, and budget.

Best types of boilers for homes
Household sizeBest boiler type
Small to medium-sized homes with lower hot water and heating demandsCombi boilers
Larger households with high hot water demandsConventional boilers or system boilers
Larger spaces or homes with many water outletsSystem boilers

It’s important to note that every home is different, and the right boiler type for your household may be different from your neighbour’s. Consulting a heating professional can help determine the most suitable boiler option for your home.

But how long and stressful can finding a professional be? It can take hours, days and precious weekends of independent searches! And still, you might not find a trusted engineer or anyone available within your location.

Fortunately, GreenMatch can help you avoid all the stress. Simply fill out a 30-second form and we’ll provide you with 3 quotes from certified boiler engineers near you. Our services are free and non-binding. Compare the prices with no obligation to accept any of the quotes you receive. Click below to begin.

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FAQ

Anna Brui
Written by Anna Brui, Writer

Anna, a Writer at GreenMatch, transitioned from teaching to content creation, fueled by her passion for renewable energy and sustainability, inspiring readers to embrace eco-friendly practices.

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