Installing a new boiler is a major decision and with so many options available, how do you know which boiler is the best one for your home? Before making this decision, it’s important to think about your current and future heating and hot water needs. You should consider how much hot water you and your family use, the size of your property, the fuel that is available to you, your existing system and the types of boiler you can have installed. 

You may also want to consider other factors such as energy efficiency and options for renewable energy use. To help you decide which boiler is right for you, we’ve prepared this at-a-glance guide.

What are the different types of boilers?

Before we get into the specifics of how to choose a boiler based on your heating needs and the size of your home, it’s important to know what types of boiler there are to choose from.

Conventional boilers

A conventional boiler is able to heat water up and store it in a hot water tank, keeping it warm for hours until it is needed. Once the stored hot water runs out, you will need to wait for more to be heated and the tank to be refilled.

These systems are better for larger homes that have multiple bathrooms and lots of radiators, however the tank can take up a considerable amount of space. Many people use the cupboard where the tank is stored as an airing cupboard. 

Combi-boilers

Combination boilers, commonly known as combi boilers, are the most popular boiler choice in the UK. They work by providing on-demand hot water directly from the mains without having to be connected to a storage tank. As a combi boiler provides hot water at mains pressure, it allows you to use a shower without the need for an additional shower pump.

All of the components are contained within one unit and there is no need for a separate hot water tank, making these boilers ideal for properties with limited space.

For those homes with a little more space, there is a type of boiler known as a storage combi. They work like a combi boiler, however they have a hot water tank similar to a conventional system that allows excess hot water to be stored and used later.

System boilers

System boilers work by directly supplying hot water to a storage cylinder and the radiators in your home. Similar to a combi boiler, the main components of this system are stored in one unit, making installation and servicing simpler. These types of boiler are ideal for properties with more than one bathroom or those that require more hot water than a combi can provide.

Choosing the right type of boiler

Now that you’ve been introduced to the three main types of boiler available, you should have a think about which one will be most beneficial for you, depending on your existing system and how much space you have to house it.

Available Space

The space available in your home could dictate the type of boiler that’s most suited to you. Most smaller properties have limited storage space, which may make it impossible to house a separate hot water tank. For instance, you may not have the space for a boiler, a large hot water tank and a cold water tank, therefore, a combi boiler would likely be the better choice. 

Existing system

It is important to think about whether or not you wish to keep the same system as that already existing in your home. Usually it is best to retain the same system from the perspective of cost and practicality, however there may be occasions when a change to another system may be better. This is more likely to be the case for older homes as newer builds will usually have the optimum system in place. Bear in mind that different systems will also require different amounts of space and may not always be suitable.

Hot water

The kind of boiler you want will also depend on your hot water usage. If there is likely to be a demand for hot water simultaneously at different outlets, then a system boiler or conventional boiler, which includes a hot water cylinder, may be more suitable than a combi boiler, however this will depend on whether there is sufficient space available.

Choosing the right size of boiler

Once you’ve decided on a boiler type, it’s important to select one that is the right size and can keep up with the heating and hot water demands of your home. For instance, a two-bed terraced house will need a smaller boiler than a five-bedroom detached house.

Hot water demand

One of the first considerations when deciding on the size of your boiler is how much hot water you will use or are likely to use in the future. If you have a young family, your needs will likely increase as the children get older.

For most households with a single bath and shower, a 24-30 kW boiler is generally recommended. Where there is an additional en-suite bathroom, it may be advisable to choose a larger 30-35 kW boiler.

If, however, you have multiple bathrooms that are likely to be in use at the same time, a system boiler that stores hot water in a storage cylinder may be more suitable. A system boiler pre-heats and stores the hot water in a cylinder with the added benefit that its output can be sized on your home’s heating demand. 

Size of property

As well as providing your hot water, your boiler will probably be the main source of heating for your property. This means that it is essential to choose a boiler that is large enough to provide sufficient heat output to supply your entire property. Domestic boiler size is measured in terms of heat output, which typically ranges from 5 to 35 kW. 

For conventional and system boilers, you should avoid choosing a boiler that is too big for your home, for example, installing a boiler that has a capacity to supply 15 radiators when your flat only has a few. This will only result in a more costly energy bill and is a waste of gas and electricity.

For combi boilers, the boiler size is usually determined by the hot water demand, a qualified heating installer will assess this for you prior to final recommendation and fitting.

Heat loss

There’s no point having an efficient boiler and heating system if most of the heat that’s being generated is escaping your home. Not only is this a waste of energy but you could receive an unexpectedly high bill from your energy supplier.

There is a calculation that can be used to work out how much heat your property is losing. It takes into account the area of the room, the number of radiators, the quantity of doors and windows and the quality of insulation in your home. An expert is able to calculate how much heat your house will lose on the coldest day of the year and use this information to work out the optimum boiler size.

You shouldn’t oversize your boiler to compensate for heat loss. In the past, it was common practice to choose an oversized boiler that was as much as 30 per cent bigger than required. However, with advances in technology, this is no longer necessary and will only result in wasted energy, leaving you out of pocket.

Looking to replace your gas boiler?

Choosing the right fuel type

Most homes are connected to the electricity and gas mains supply, so running appliances with these fuels isn’t difficult. However, for those in more rural locations or without access to gas, a gas boiler isn’t necessarily an option. Oil boilers should be considered too.

You may even want to look into green energy sources, however, these will have an impact on your choice of heating system and boiler, too. 

Mains gas

The most common fuel type in the UK is mains gas, with the majority of UK homes already connected. With a gas boiler there is a constant supply and as far as non-renewable energy is concerned, it is considered to be the cleanest type of fuel.

Oil

Oil is the most common alternative for properties that are not connected to the gas network and is currently used by an estimated 4.3 million UK households. Unlike gas combi-boilers, oil boilers tend to be non-condensing and floor standing, therefore may require more space. They also tend to offer a lower hot water flow rate in comparison.

Biomass and alternative energy

Finally, consider biomass and other forms of alternative energy. if you have storage space and are able to burn fuels that require a flue, you may wish to consider a biomass system. A more eco-friendly, alternative choice, these boilers are powered by a sustainable fuel source. 

Typically fuelled by wood pellets, chips or logs, they can help to protect the environment as well as saving on your energy bills. Other alternative approaches to energy for your boiler that are seeing increasing popularity are heat pumps and fuel cell technology which are increasingly compatible with modern boilers.

Future energy sources

You may also wish to consider whether your boiler is designed with future energy sources in mind. Some advanced gas boilers are now made to be compatible with solar energy, whilst oil systems can be equipped to be partially run on bio-oil mixes, helping to make them future proof and more ecological.

Which boiler is best for my house?

Now we’ve run through the types of boiler, the fuel they run on and how to choose the correct size for your home. Below, you can find some more specific examples based on the type of home you live in.

What is the best boiler for a three-bed semi?

Semi-detached houses tend to hold their heat better than detached homes. This is because there are fewer external walls through which heat can be lost, as your house is attached to your neighbour on one side. Therefore, the heat from your neighbour’s home will help to insulate your own house, reducing heat loss.

For a three-bedroom semi with one main bathroom, we’d typically advise that you install a storage combi boiler. These systems will heat water on demand, however they also have an integrated tank for storing some hot water too. This means you don’t need a separate bulky storage tank that could take up precious space.  

What is the best boiler for a four-bedroom house?

If you live in a four-bedroom home that has multiple bathrooms and family members that wish to have showers at the same time, a conventional boiler could be the best choice for you. They easily meet the demand of large households that contain lots of radiators.

What is the best boiler for a three-bed terraced house?

For a three-bedroom terraced house, we’d advise a compact combi boiler that can fit snugly into a standard kitchen unit or other similar cupboard elsewhere in the home. It’s ideal if you don’t have a large amount of storage space at home.

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