From fuel types to the size of the boiler to economic costs, there are a lot of factors to consider. In this guide, we will try to address everything that you need to know when buying a new boiler.

Choosing the right KW boiler is essential so that you can efficiently heat your house.

Types of boiler

Within the UK, the majority of homes use gas-fuelled heating systems. However, there are some households which are not connected to the gas network and will use an alternative fuel type.

The types of fuel used for heating systems in the UK include:

• Gas boiler
• Oil boiler
• LPG boiler (liquid petroleum gas)
• Wood-burning stove fitted with a back boiler

What is the best gas boiler for my house?

There are three types of gas boiler to choose between for UK households.

Read more about the Types Of Boilers For Central Heating.

Combi Boiler (combination)

A combo boiler offers on-demand hot water for heating and domestic use. This is a space-saving system as it only requires the installation of a boiler and does not need a water tank.

This makes it ideal for small flats as well as large homes.

Read our guide to the Best Combi Boilers.

Heat only boiler (conventional)

The conventional boiler option requires a hot water storage cylinder along with a cold water feed tank. This is usually kept in the loft in a house with lots of space.

This option is perfect for homes with multiple bathrooms that require hot water at the same time.

System Boiler

A system boiler is similar to a conventional boiler but without the need for a cold water storage tank.

This type of boiler works best for homes with low water pressure.

Best Boilers and Prices

When tying to decide on the best boiler to buy for your home, you will need to think about the size of your home.

How many bathrooms do you need hot water for?

How many bedrooms does your house have?

Is there a demand for hot water in multiple locations at the same time?

Best boiler to buy for a small flat

Installing the right boiler for a flat or small home is important if you want to avoid increased heating bills.

Small Combi Boilers

A small house with up to 10 radiators and a single bathroom will find a combi boiler with an output of 24-28kW adequate for their heating needs.

A combi boiler offers hot water on demand and will not take up too much space when installed.

Below are some of the most popular boilers available for small flats:

A gas combi is the most common type of combination boiler as it is usually the cheaper option. However, an electric combi can offer up to 100% efficiency.

Following the introduction of Boiler Plus legislation in April 2018, all combi boilers manufactured or installed must have a minimum efficiency level of 92%.

This means that whatever combi boiler you choose from this date, it will meet these high-efficiency standards.

Best boiler to buy for a two-bed or three-bed house

Choosing the right boiler for a 2 or 3 bedroom house means that you need a reasonably powerful system.

Your boiler needs to be efficient enough to heat your home while not being too powerful and costing more in fuel bills.

Which combi Boiler?

A combi boiler is a compact heating system which is designed to fit into small spaces. Since you will not need to install additional water tanks or cylinders, this is a great space-saving option.

1-2 bedroom house

For a 1-2 bedroom house with up to 10 radiators, you should be fine with a boiler that has an output of 24-27kW.

3-4 bedrooms

If your home has between 3-4 bedrooms you may need a more powerful heating system. For homes with up to 15 radiators and 1-2 bathrooms, you will need a boiler that provides an output of 28-34kW.

Below are some popular combi boilers which will be suitable for a typical 2 bedroom house:

Best boiler to buy for a four-bed house

The type of boiler required for a four-bedroom house will depend on the number of bathrooms that you use. The best boiler to buy will need to cope with heating all these rooms and supplying water to each bathroom.

Once a house requires a certain amount of hot water, even the most powerful combi boiler may not be able to satisfy your needs.

When to choose a combi boiler

A combi boiler does not store hot water in a tank or cylinder which means that you may be restricted on the amount of hot water available.

You will usually be OK installing a combi boiler for a four-bedroom house with up to 2 bathrooms. However, once you have more than 2 bathrooms in your home, you may require a system boiler.

When to choose a system boiler

System boilers hold hot water in a cylinder which makes it available for multiple bathrooms when it is required.

For a four-bedroom house with up to 20 radiators, you will require a boiler with an output of 35-42kW.

Best System Boiler

If you live in a 4 Bedroom House with 2 or More Bathrooms then a system boiler would be the most appropriate boiler to heat your home.

Worcester Bosch and Vaillant are two of the most popular manufacturers of system boilers in the UK.

Remember that, alongside the boiler installation, you will also need to have a hot water cylinder installed. This is commonly fitted into the loft space.

The benefit of installing a hot water cylinder is that you will have hot water available for more than one tap or shower working at the same time.

This makes a system boiler more efficient than a combiner’s boiler in homes with more than 2 bathrooms.

Below are some of the most popular system boilers for your home:

A typical system boiler will cost over £1100 and will require an installation charge of between £500 and £1000.

What are the best and worst boiler brands?

We have created a complete guide to help you find the most trusted boiler brands in the UK.

Our guide is based on customer research carried out by Which to help you make the right decision for your home.

You can read more here about the best and worst boiler brands in the UK.

Best boiler to buy for a home with low water pressure

If you have a combi boiler you may experience low water pressure if you are putting a lot of demand on it from multiple water outlets. For example, if you have a shower which only provides a low-pressure flow of water, your boiler may not be powerful enough to cope with the hot water demands of your home.

The flow rate of a boiler is the amount of water it can provide to taps and showers while it is working. A combi boiler should be powerful enough to offer a flow rate for a shower of 12 – 15 litres a minute.

Your combi boiler is also mains fed which means that it is restricted by how much water can be provided by the mains supply.

In a situation where the flow from the mains is less than that offered by your boiler, you will not be benefiting from an increase in boiler flow capabilities.

An alternative to a combi boiler may be required if you are not able to increase the water pressure in your home to the desired rate.

Both a conventional boiler and a system boiler can provide a high level of water pressure throughout the home. These heating systems are also compatible with power showers while a combi boiler is not.

If you live in an area with low water pressure, a conventional boiler is the preferred option if you have the space available to install it. A conventional boiler will require a cold water storage tank to be fitted in your home along with a hot water cylinder.

A system boiler may be a more practical option if space is limited since you will not need to install the cold water feed tank.

While both options are a solution to homes with low water pressure, a conventional boiler and a system boiler will not be able to produce hot water on demand.

Only a combi boiler can heat water as it enters your home through the mains. The alternative heating systems require a cylinder of water to be preheated before use.

Which is the most efficient boiler for you?

Boiler efficiency is important if you are trying to lower fuel costs and reduce CO2 emissions produced from your home.

On average, a UK home will produce about 60% of the entire CO2 produced from central heating. This means that boiler efficiency is a key factor in reducing energy bills when you are considering installing a new boiler.

The good news is that most modern boilers will be around 90% efficient which is a huge saving compared to the older boiler that you will be replacing.

A non-condensing boiler will on average be about 1/3 less efficient than a modern boiler that uses a condensing system.

To get the most efficient boiler for your home, you will need to consider which boiler is the right size for your home.

What size KW boiler do I need?

The best boiler to buy for your home will depend on the size and quality of the insulation installed in the building.

The guide below will compare various properties and offer the KW size boiler that is usually recommended.

When choosing which size boiler you require, you need to calculate the specific requirements for your home.

The size of your boiler will depend on the number of people using your home and the number of bathrooms that require hot water delivered to them.

Choosing the right size boiler for your home will depend on two factors:

• What are the water capabilities of the boiler
• Will the size of the boiler fit the space available

A heating engineer will usually be able to guide you towards the right size boiler for your home.

The age of your property will also affect the size of the boiler required. Older homes are generally less insulated than modern homes so the quality of insulation is a factor in the type of boiler required.

Combi Boilers Size Charts:

What if I Experience Central Heating Problems?

Over the years, there is a good chance that you may experience problems with your boiler or central heating system.

There are a number of common faults that can cause a failure in your heating.

If you want to prevent boiler faults or calling out an expensive emergency repair engineer, it helps to know what can go wrong.

Luckily, we have created The Ultimate Guide to Heating Problems and Heating Repairs.

Do I need an annual boiler service?

Once you have purchased your boiler, you will need to carry out an annual boiler service to ensure that it continues to work properly.

There are many benefits of having your boiler services on a regular basis which we have included in our guide: Should I get an Annual Boiler Servicing?

A boiler servicing will help keep your central heating working throughout the winter months when you need it the most.

You will also benefit from a longer life span of your heating system which will save you the expense of replacing your boiler earlier than necessary.

An annual boiler servicing is recommended by all boiler manufacturers. But if you want to be sure that you are getting the best from your boiler service, read our article: What Should I Expect From A Boiler Service?

We hope that the information in this article will help you find the best boiler to buy for your home.