Are you looking to replace your old boiler? Or maybe you want to install a new system from scratch? In any case, you will be confronted with the arduous problem of selecting a new boiler. There are numerous factors to consider when choosing the ideal boiler for you, ranging from the type of boiler and its brand to its size and energy efficiency. But where do you even begin?

In this blog post, we’ll go over the different types of boilers as well as their benefits and drawbacks. Furthermore, we will guide you through the process of selecting the right boiler size, fuel type, and brand. So, let’s get started and learn how to choose the best boiler for the heating and hot water demands of your home.

What are the different types of boilers available in the UK?

Combi, system, and heat only boilers are the three primary types of boilers offered on the UK market. They are available in a range of sizes, efficiency ratings, and brands, and each type has its own set of features, advantages, and disadvantages.

Combi or combination boilers are small and compact appliances where the water heater and central heating boiler are incorporated into a single unit. They are one of the most frequent types of boilers in the UK. One of the distinctive features of the combi boiler is that it heats water on demand as it runs through the unit. As a result, no separate tank is required. Such a device might be an ideal solution for small apartments or houses with limited room.

System boilers supply hot water to a storage cylinder and radiators directly. There is no cold-water tank. They are designed to maintain consistent water pressure, ensuring that a steady flow of hot water is always available. These boilers can be a good solution for larger homes because they are able to deliver hot water to a number of faucets at the same time.

Heat-only boilers, also called regular or conventional boilers, incorporate both a hot water storage cylinder and a cold water tank. They utilise the hot water from the cylinder in order to feed the taps and heat radiators throughout the house. The regular boiler, like the system boiler, may deliver hot water to multiple outlets simultaneously, making it ideal for larger families. However, because this appliance includes both a cold water tank and a hot water storage cylinder, it takes up more space compared to the system boiler.

How to choose the right type of boiler?

If you want to find the ideal boiler for your needs, you must consider numerous factors, including the size of your home and the amount of space available to fit your boiler, the amount of hot water you use, whether you want a more energy-efficient boiler, and others. This section will go over everything you should consider when purchasing a new boiler.

The property’s size

How big is your home? Do you live in a little apartment or a large house? How many rooms are there in total? These are important questions you should take into account when choosing a new boiler. If you live in a tiny house or flat, consider purchasing a small combi boiler. If you need to heat a large property, a regular or system boiler is the way to go.

Your hot water needs

The right boiler for you will also greatly depend on the hot water usage. Consider the number of bathrooms and outlets in your home as well as the number of people who live there. For example, large families who live in large homes and have a high hot water demand will benefit the most from a system boiler or a heat-only boiler.

Space available in your home

How much space do you have in your home to accommodate the boiler? It is critical to select an appliance that will fit in the specified area. For example, if you live in a small apartment, you should avoid conventional boilers, which occupy a lot of room.

Your current heating system

If your existing system is still in good working order, you may wish to keep it and merely replace your boiler. This is usually the less expensive and more practical alternative. However, in some circumstances, the entire system may need to be replaced. This is particularly true if the system is old and inefficient. It is best to have a qualified heating expert inspect the old system and make advice on whether it should be replaced or updated in conjunction with the new boiler.

Energy efficiency

When purchasing a new boiler, you should look for one with a high energy efficiency rating. While more efficient appliances often have higher initial costs, the savings on energy bills can more than outweigh that cost over time. The rating of energy efficiency is commonly given as a percentage or a letter grade (A-G), with A-rated boilers being the most efficient and G-rated boilers being the least efficient. To achieve optimal energy savings, the Energy Saving Trust recommends selecting a boiler whose energy efficiency rating is at least 92%.

Type of fuel

You should choose a boiler that is compatible with the type of fuel used in your building. The majority of households in the United Kingdom have access to a gas main supply and electricity, with gas combi boilers being the most popular choice. However, those who live in more remote areas or do not have access to gas, often opt for an oil boiler. A biomass boiler is another alternative for people looking for a more environmentally friendly solution. It is important to consider your location and fuel availability when deciding which kind of boiler is ideal for you, whether it is a gas boiler, an oil boiler, or an electric boiler.

Combi boilers

Combination boilers are compact devices which are designed to provide both heating and hot water. These boilers are efficient and don’t take up too much space. They are one of the most widely used types of boilers in the United Kingdom.

How do combi boilers work?

The combination boiler works by heating the water right from the mains when you start bathing or turning on the hot water tap. This boiler type does not have a separate hot water tank or cylinder to store hot water.

If you run the hot water faucet, the internal diverter valve of the boiler will send the water to the heating element, which will heat the water as it passes through. Then the hot water will be delivered to your tap or shower at the desired temperature.

When it comes to heating, the combi boiler uses a heat exchanger in order to generate heat for radiators and water circulated throughout the heating system. Heat is transferred to the water through the heat exchanger by burning gas or oil in the boiler’s burner.

Pros and cons of combi boilers


  • They are compact and space-saving. There is no separate hot water storage tank or cylinder in these boilers. Instead, all of the components are incorporated into the boiler unit, allowing it to fit into compact areas such as kitchen cabinets.
  • They can be more energy efficient. Combi boilers heat hot water directly when you turn on the tap or shower. They do not preheat it and then store it in a tank. As a result, these boilers might help you save money on your utility expenses.
  • These boilers provide hot water on demand. With a combi boiler, you cannot run out of hot water. Basically, you can have it whenever you desire. There’s no need to wait for the tank to heat up.
  • Combi boilers are easier to install. The installation of the combi boiler is usually simpler since they do not require a separate water tank or cylinder. This can save you time and money.


  • There might be water pressure problems. Combi boilers require sufficient water pressure to operate effectively. Therefore, if your home has low water pressure, you may experience issues with the boiler.
  • They do not have a back up hot water supply. This means that if your boiler breaks down or needs to be serviced, you may be without hot water until it is repaired.
  • They might not be suitable for larger properties. Combi boilers can deliver hot water on demand, however, they can struggle to supply more than one tap. So, if your property is large and has multiple bathrooms, consider installing a different type of boiler.

Learn how you can turn off the water supply to your house.

System boilers

System boilers provide hot water and heat to properties using a hot water cylinder. They are most typically found in larger homes with multiple bathrooms and high demand for hot water.

How do system boilers work?

System boilers heat water in a central heating system, which is subsequently stored in a special cylinder. This type of boiler has an expansion vessel, which allows the system to withstand fluctuations in water pressure without the need for a feed and expansion tank in the loft.

The system boiler draws hot water from the cylinder and delivers it to the shower and faucets. When you use hot water, the device will heat the water in the cylinder again to guarantee that it is constantly accessible.

Pros and cons of system boilers


  • These boilers provide hot water to multiple outlets. System boilers can serve multiple showers and faucets at the same time without reducing water pressure.
  • They don’t take up too much space. System boilers can be more space-efficient than conventional boilers since they do not have a separate cold water storage tank.
  • They can be energy-saving. These boilers typically include a thermostat and a timer, allowing you to easily control them and ensuring that they only deliver heating when needed.


  • You may need to wait for the water to reheat. Unlike combi boilers, which heat water straight from the mains, system boilers store hot water in a special container (cylinder). So, if you use all of the hot water, you’ll have to wait a set amount of time for it to reheat.
  • They require proper water pressure to function well. Older properties are more likely to have low water pressure, which can interfere with the system boiler’s operation.

Heat only boilers

A heat only boiler is a type of boiler that incorporate both components a hot water cylinder and a cold water storage tank. Using them the device can provide homes with the necessary hot water and heating.

This boiler is frequently referred to as a regular or conventional boiler.

How do heat only boilers work?

This boiler type operates similarly to system boilers – the water in the central heating system is heated first and then stored in a hot water cylinder until it is needed. Regular boilers, unlike system boilers, feature a cold water storage tank, which in most cases is placed in the loft. This component provides fresh water to the system, which is subsequently heated by the boiler and pumped around the system.

Pros and cons of heat only boilers


  • They are easy to maintain. One of the primary benefits of this boiler type is that it is generally reliable and simple to maintain, with most parts easily available and easy to replace.
  • They are compatible with solar thermal panels. You can connect your heat only boiler with solar panels. This can help you save money on electricity while also lowering carbon emissions. The heat only boilers may also be connected to ground-source heat pumps in a hybrid system.
  • Regular boilers can be a more cost-effective option. These boilers are usually less expensive to install compared to other types of boilers. This is especially true if you already have a hot water cylinder and cold water storage tank in place.
  • They can work well in older properties with low water flow rates. Heat only boilers provide a high hot water flow rate, making them an excellent solution for older homes where the water flow rates are low.


  • They require a lot of space. The conventional boiler can be a quite space-consuming appliance. These kinds of boilers use both a separate hot water cylinder for storing hot water and a cold water tank for feeding the system. These components usually take up valuable storage space in the home.
  • They are less energy-efficient. These boilers are not as energy-efficient as other types of boilers because they need to regularly heat and store hot water.

Other considerations

Aside from the type of boiler, there are a few additional factors to consider when selecting a boiler for your home. These include the size and the brand of the appliance as well as the fuel type it uses.

What size boiler do you need?

When you are buying a new boiler, it is important to ensure that it is of the correct size so that it can efficiently heat your home and provide hot water. But, what you should do in order to determine the correct size of boiler for your home?

First, you will need to find out the heat requirement for your home. To do this, you will need to take some measurements and make some calculations. These include the total floor area of your home, the amount of heat loss, the required heat output of your boiler and others.

When determining your home’s heating requirements, you will also need to consider factors such as the local climate and how warm you want your property to be. In the United Kingdom, the typical heating need is 50-60 watts per square meter. This, however, might vary depending on factors like insulation and window type.

Another essential factor that you need to consider when choosing the size of your new boiler is the hot water demand. This is typically measured in litres per minute (LPM) and is affected by the number of people in your home and their habits (such as shower frequency).

Keep in mind that selecting a boiler that is too large may result in increased energy bills and poor efficiency. A small boiler, on the other hand, will struggle to meet your heating and hot water needs. It is best to consult It is best to seek the advice of a professional heating engineer who can help you achieve the greatest balance of efficiency and performance.

How to choose the right fuel type?

The first factor you should consider when deciding on a fuel type for your new boiler is the availability of fuel in your location. Most UK households are connected to a gas network, so running gas boilers is usually simpler. Oil boilers, on the other hand, are a choice for residences located in more rural locations or without access to gas.

In addition, fuel costs are also a major factor. It is a good idea to look into local fuel prices to see which fuel type will be the most cost-effective in the long run. Also, bear in mind that different fuel types have varying efficiency ratings, which might affect the overall performance of your boiler as well as your heating bills. Gas boilers, for instance, are more efficient than oil boilers. This means they will use less fuel to heat your home, lowering your heating bills.

Another critical factor to consider is the environmental impact of your chosen fuel type. Gas, for example, is a cleaner-burning fuel than oil, and hence has a reduced carbon impact. Biomass boilers and air source heat pumps can also be smart solutions for those trying to lessen their environmental impact. However, it is important to note that their initial installation costs can be higher than other heating systems. Furthermore, heat pumps and biomass boilers typically take up a lot of room.

Before making your final decision, it is best to consult a professional heating engineer. The specialist can assist you in choosing the appropriate fuel type based on your specific needs and budget.

What are the best boiler brands?

In terms of boiler brands, there are many options available in the UK. In order to decide what is the best one for you, you should consider factors such as quality, reliability, and price. Here we have gathered the top brands of boilers in the UK based on customer satisfaction and industry reputation.

  • Vaillant. It is a well-known boiler brand in the UK, with a reputation for providing high-quality, long-lasting boilers. The company offers a variety of gas boilers, oil boilers, and LPG boilers. Vaillant boilers are usually easy to install, use and maintain.
  • Worcester Bosch. This is another reputable boiler brand in the UK that manufactures a variety of gas, oil, and LPG boilers for residential and commercial usage. The company is known for providing high-quality and reliable boilers, and its products have received numerous accolades.
  • Baxi. It is a well-established company with a strong reputation for offering quality boilers. Baxi boilers are popular with their reliability and efficiency. Many models have an A-rating for efficiency.
  • Ideal. This is a popular brand known for producing quality and affordable boilers. The company won numerous awards for their products and customer service.

There is no one boiler brand that is the best for every home, and it really depends on your specific needs, budget, and preferences. Before you make any decision, do your research and speak with a professional heating engineer.

How to get the best boiler installation?

Choosing a reliable and skilled installer is just as important as selecting the right boiler. Even if you buy a superb boiler, if you make the wrong installation decision, you may have trouble with the appliance. Not to mention the risks associated with improperly fitted boilers.

Here are some tips that may help you get the best boiler installation.

  • Be sure to choose a Gas Safe Registered installer. It is critical to utilize only Gas Safe registered installers for any work involving gas appliances, including installations of gas boilers. To confirm that the installation you are contemplating is Gas Safe registered, you may check their credentials on the Gas Safe Register website.
  • Check the certifications of the installer. Look for installers who have been certified to install the boiler manufacturer’s products. This ensures that the installation is done according to the manufacturer’s standards and that any warranties are not void.
  • Ask about the aftercare services the installer offers. Make sure to inquire about the aftercare services offered by the installer, such as annual boiler servicing and repairs.
  • Get multiple quotes. You may want to get quotations from several different installers so you can compare their pricing and services.
  • Hire a local boiler installer. Hiring a national installation is frequently a more costly option. Local boiler installers, on the other hand, do not have high overheads, so their service charges can be lower.

Choosing a good and trustworthy boiler installer is important for guaranteeing safety, efficiency, warranty validity, longevity, and peace of mind.

Frequently Asked Questions

Why is boiler efficiency important?

Having a more efficient boiler is important because it can help lower both your heating costs and carbon footprint. In addition, a boiler with a greater energy efficiency rating can heat your home more evenly providing better comfort for you and your family.

Is a heat pump as good as a boiler?

Both heat pumps and boilers have their distinct features and come with some benefits and downsides. Which one is better depends on your individual situation and heating and hot water demands. Heat pumps use renewable energy sources. They work by extracting latent heat from the air outside and using it to heat water, which is then circulated throughout the house through radiators or underfloor heating. As a result, they can be more energy-saving and environmentally friendly than standard boilers.

Heat pumps are, however, more expensive to install at first, and their performance may be affected by your home’s insulation and the local environment. Boilers, on the other hand, are frequently less expensive to install and may be a better option for properties that require a large amount of heat. They are also more reliable in extreme weather conditions such as cold winters.

Is a condensing boiler the same as a combi boiler?

A combi boiler and condensing boiler are basically two different types of boilers. However, some combination boilers are also condensing boilers.

Condensing boilers are highly efficient devices that use a heat exchanger to extract heat from the combustion gases while also condensing the water vapour. As a result, they are more efficient than ordinary boilers, which merely vent hot gases outside.

The combi boiler, on the other hand, is an appliance where the central heating boiler and water heater are combined into a single unit. These boilers offer hot water on demand and do not require a separate hot water tank. They can be condensing or non-condensing, depending on their design. Check out our article on the differences between condensing and non-condensing boilers for more information.