What kind of boiler do I need for my home?

Installing a new boiler is a major decision and there are many options available. So how do you know which boiler is the best one for your home?

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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 quick 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.

Combi boilers

Combination boilers, commonly known as combi boilers, are a popular boiler choice in North America. They work by providing on-demand hot water directly from the boiler without having to be connected to a storage tank. 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 an integrated hot water tank that allows excess hot water to be stored and used later.

System boilers

System boilers work by directly supplying hot water to a storage tank 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 boilers are ideal for properties with  multiple bathrooms or those that require more hot water than a combi can provide.

Vitodens 200-W gas condensing system boiler

Choosing the right type of boiler

Now that you've been introduced to the main types of boiler available, you should 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 for you. Most smaller properties have limited storage space, which may make it difficult or impossible to install a separate hot water tank. So if you don't have the space for a boiler and hot water tank, then a combi boiler would probably be the better choice.

Existing system

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

Hot water

The kind of boiler you need will also depend on your hot water usage. If it's likely there will be a demand for hot water at multiple fixtures in your house at the same time, then a system boiler with a hot water tank is probably more suitable for you than a combi boiler. However, this will depend on whether there is sufficient space available for this kind of heating system.

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 example, a two-bedroom townhouse will usually 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 households with a single bath and shower, a smaller boiler is generally recommended. Where there is an additional en-suite bathroom, it may be advisable to choose a larger capacity boiler. If you have multiple bathrooms that will be used at the same time, a system boiler that stores hot water in a storage tank may be your best option. We recommend getting advice from a heating professional who can help determine the optimum size of system for your home.

Size of property

As well as providing your hot water, your boiler will probably be the main source of heating for your home. This means that it is essential to choose a boiler that is large enough to provide sufficient heat output to supply your entire property.

For system boilers, you should avoid choosing a boiler that is too big for your home, e.g. installing a boiler that has a capacity to supply 15 radiators when your home only has a few. Getting an oversized boiler will result in a more costly heating bill, as well as wasted fuel and electricity.

For combi boilers, the boiler size is usually determined by the hot water demand. A qualified heating contractor can assess this for you prior to final recommendation and installation.

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 also receive an unexpectedly high bill from your fuel supplier.

There is a calculation that can be used to determine how much heat your building is losing. It takes into account the area of the rooms, the number of radiators, the quantity of doors and windows and the quality of insulation in your home. A home heating 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% bigger than required. However, with advances in technology, this is no longer necessary and will only result in wasted energy and money.

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Choosing the right fuel type

Many homes are connected to natural gas supply lines, so running appliances with this fuel isn't difficult. However, for those in more rural locations or without access to gas, a gas-fired boiler isn't always an option. Oil boilers can be considered too.

You may also want to look into green energy sources, such as biomass heating systems which are carbon neutral.

Natural gas and propane

The most common fuel type in North America is natural gas (NG), with the majority of homes already connected. With a natural gas boiler there is a constant fuel supply, and as far as non-renewable energy is concerned, it's considered to be the cleanest type of fuel. Many gas boilers are also able to operate using liquid propane (LP) when natural gas in not readily available. This is common in many rural areas.


Oil is also a common alternative for properties that are not connected to the gas network. Unlike gas boilers, oil boilers tend to be non-condensing and floor standing, so they 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 want to consider a biomass system. A more eco-friendly choice, these boilers are powered by a sustainable fuel source, typically either wood pellets or chips.

Other alternative approaches to heating that are seeing increasing interest are air source heat pumps, ground source heat pumps and fuel cell technology, which are increasingly compatible with modern boilers.

Future energy sources

You may also want to consider whether your boiler is designed with future energy sources in mind. Some advanced gas boilers are now designed to be compatible with gas mixtures containing hydrogen, and there are oil heating systems which can be equipped to run on biofuel mixes, helping to make these systems future-proof and more ecological.

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Which boiler is best for my house?

Now that we've run through the types of boilers, the fuel they run on and how to choose the correct boiler size for your home, let's consider some specific examples based on the type of home you live in.

What's the best boiler for a three-bedroom 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.

For a three-bedroom semi with one main bathroom, we'd typically advise that you install a combi boiler. These systems will heat water on demand, and provide heat to your home's radiators, in-floor heating or fan coils. This means you don't need a separate storage tank that could take up precious space, if space is at a premium. If you do have adequate space in your mechanical room, a system boiler plus hot water storage tank is an equally good choice.

What's the best boiler for a four-bedroom house?

If you live in a four-bedroom home that has multiple bathrooms and family members that might have showers at the same time, a system boiler with hot water storage tank could be the best choice for you. They easily meet the demands of large households that have large hot water needs.

What's the best boiler for a three-bedroom townhouse?

For a three-bedroom townhouse, we'd advise a compact combi boiler that can fit snugly into a closet, under stairs or in the corner of a small mechanical room. These combi boilers are ideal if you don't have a large amount of storage space at home.

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