What type of new boiler is suitable for my home?

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 varieties of boilers are available?

Prior to delving into the details of selecting a boiler according to your heating requirements and home size, it’s essential to understand the various types of boilers available for consideration.

Conventional Boilers

Conventional boilers have the capability to heat water and store it in a hot water tank. Therefore maintaining its warmth for extended periods until required. When the stored hot water is depleted, you must wait for it to be reheated and the tank refilled. These systems are more suitable for larger homes with multiple bathrooms and numerous radiators. However, it’s important to note that the tank can occupy a significant amount of space. Often, individuals utilise the cupboard housing the tank as an airing cupboard.


Combination boilers, often referred to as combi boilers, stand as the preferred choice of boiler in the UK. They operate by delivering hot water on demand directly from the mains, eliminating the need for a connected storage tank. Because a combi boiler supplies hot water at mains pressure, it facilitates the use of a shower without requiring an additional shower pump. All essential components are housed within a single unit, eliminating the necessity for a separate hot water tank. This characteristic makes combi boilers particularly suitable for properties with limited space. For residences with slightly more available space, there exists a variation known as a storage combi boiler. Operating akin to a standard combi boiler, storage combis feature a hot water tank akin to that found in conventional systems. This tank enables surplus hot water to be stored for later use.

System Boilers

System boilers function by supplying hot water directly to a storage cylinder and the radiators within your home. Like combi boilers, the primary components of this system are consolidated into a single unit, simplifying both installation and maintenance. Such boilers are well-suited for properties featuring multiple bathrooms. Or Even those with a greater demand for hot water than what a combi boiler can accommodate.

Choosing the right type of boiler

Having familiarised yourself with the three primary types of boilers, it’s time to consider which one would best suit your needs, taking into account your current system and the available space for installation.

Space Availability

The amount of space in your home might determine the type of boiler that best fits your needs. In smaller properties where storage space is limited, accommodating a separate hot water tank could be challenging. For example, if there isn’t enough space for a boiler, a sizable hot water tank, and a cold water tank, opting for a combi boiler would likely be more practical.

Existing system

Consider whether you prefer to maintain the existing system in your home. Typically, sticking with the current system is advantageous in terms of both the cost of a new boiler and practicality. However, there might be instances where transitioning to a different system is more beneficial. This scenario is more common in older homes, as newer constructions generally have optimal systems in place. Keep in mind that various systems have different space requirements and may not always be suitable for every situation.

Hot water

Your choice of boiler will also hinge on your hot water consumption patterns. If there’s a likelihood of simultaneous hot water demand from various outlets, a system boiler or conventional boiler with a hot water cylinder might be more appropriate than a combi boiler. However, this consideration is contingent upon the availability of adequate space.

Selecting the appropriate boiler size

After settling on a boiler type, it’s crucial to choose a size that can adequately meet the heating and hot water requirements of your home. For example, a two-bedroom terraced house will require a smaller boiler compared to a five-bedroom detached house.

Water heating needs

One of the primary factors to consider when determining the size of your boiler is your current and anticipated hot water usage. If you have a growing family, it’s likely that your hot water needs will increase over time as the children grow older.

For households with a single bath and shower, a boiler with a capacity of 24-30 kW is typically recommended. If there is an additional en-suite bathroom, opting for a larger boiler with a capacity of 30-35 kW may be more appropriate.

However, if your home has multiple bathrooms that are expected to be in use simultaneously, a system boiler with a storage cylinder for hot water may be a better option. A system boiler pre-heats and stores hot water in a cylinder, with the added advantage that its output can be tailored to match your home’s heating requirements.

Property Size

In addition to supplying hot water, your boiler is likely the primary source of heating for your property. Therefore, it’s crucial to select a boiler with adequate heat output to effectively heat your entire home. Domestic boiler size is typically measured in terms of heat output, ranging from 5 to 35 kW.

For conventional and system boilers, it’s important to avoid choosing a boiler that exceeds the heating needs of your home. For instance, installing a boiler designed to supply heat to 15 radiators in a flat with only a few radiators will result in higher energy bills and unnecessary gas and electricity consumption.

With combi boilers, the boiler size is typically determined by the hot water demand. A qualified heating installer will assess this requirement before making a final recommendation and fitting.

Heat loss

Having an efficient boiler and heating system is pointless if a significant portion of the generated heat escapes your home. Not only does this waste energy, but it can also lead to unexpectedly high energy bills from your supplier.

There’s a calculation method available to estimate the amount of heat your property loses, considering factors such as room area, number of radiators, doors and windows quantity, and the quality of insulation. Experts can utilize this calculation to determine the heat loss on the coldest day of the year and recommend the optimal boiler size accordingly.

It’s important not to oversize your boiler to compensate for heat loss. In the past, it was common to select an oversized boiler, sometimes up to 30% larger than necessary. However, due to technological advancements, this practice is no longer required and will only result in wasted energy, ultimately costing you more.

Selecting the appropriate fuel type

For residences connected to electricity and gas mains, operating appliances with these fuels is typically straightforward. However, in rural areas or locations without gas access, a gas boiler might not be feasible. In such cases, oil boilers become a viable alternative worth considering.

Exploring green energy sources is also an option. Nevertheless, integrating these sources will influence your selection of heating system and boiler as well.

Mains gas

Mains gas stands as the predominant fuel type in the UK, with the majority of homes already connected to it. Utilising a gas boiler ensures a continuous supply, and in terms of non-renewable energy, gas is regarded as one of the cleanest fuel options available.


Oil serves as the primary alternative for properties lacking access to the gas network, currently serving an estimated 4.3 million households in the UK. Unlike gas combi-boilers, oil boilers typically lack condensing features and are floor-standing, which may necessitate more space for installation. Additionally, they often provide a lower hot water flow rate in comparison.

Biomass and alternative energy

Lastly, contemplate biomass and other alternative energy options. If you possess storage space and can accommodate fuels necessitating a flue, a biomass system might be worth considering. Representing a more eco-friendly alternative, these boilers operate on sustainable fuel sources.

Primarily fueled by wood pellets, chips, or logs, they contribute to environmental preservation while also reducing energy expenses. Other rising alternatives for boiler energy include air source heat pumps, ground source heat pumps, and fuel cell technology, which are becoming increasingly compatible with modern boiler systems.

Upcoming energy sources

You might also want to contemplate whether your boiler is designed with future energy sources in mind. Advanced gas boilers, for example, are now being manufactured to be compatible with solar energy. Similarly, oil systems can be adapted to run partially on bio-oil mixes, which helps make them more sustainable and future-proof.

What type of boiler suits my home best?

Now that we’ve covered the various boiler types, their fuel options, and selecting the appropriate size for your residence, let’s delve into more specific examples based on the type of dwelling you inhabit.

  • Three-bedroom semi-detached house: Semi-detached houses generally retain heat better than detached homes due to fewer external walls through which heat can escape, as one side of the house is attached to a neighbour. Consequently, the warmth from your neighbour’s home aids in insulating your own, minimising heat loss. For a three-bedroom semi with one main bathroom, our recommendation would typically lean towards installing a storage combi boiler. These systems provide hot water on demand while incorporating an integrated tank for storing some hot water as well. This eliminates the need for a separate bulky storage tank, which could occupy valuable space.
  • Four-bedroom house: If you reside in a four-bedroom household with multiple bathrooms and family members desiring simultaneous showers, a conventional boiler might be the optimal selection. They adeptly satisfy the requirements of large households with numerous radiators.
  • Three-bed terraced house: For a three-bedroom terraced house, we recommend opting for a compact combi boiler that can neatly fit into a standard kitchen unit or another suitable cupboard elsewhere in the home. This choice is ideal if you have limited storage space available.

Need an Engineer?

Feel free to contact Ability by filling out the form on our website, giving us a call at (+44) 01892 514495, or sending a message to info@ability.uk.com. Be assured that we prioritise rapid responses and will promptly attend to your inquiries. Our aim is to offer you the assistance and guidance you need without any unnecessary delay.

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