🕑 6 minutes read

3 Things to consider before installing a new boiler

So, you’re thinking of purchasing a new boiler? Getting a new boiler installation is a substantial investment and you need to be sure you’re selecting the right boiler to give you constant heating and hot water on demand.

Boiler quotes?

Do your research first by accessing WHICH? to find out what boiler ranks as the best from the numerous boilers currently on the market. At least it will help you to reduce the time and effort needed to trawl through countless boiler manufacturer websites and reviews, which may cause confusion after some time.

Therefore, try and keep it simple. Seeking a boiler with all the bells and whistles at a cheap price, don’t usually go hand in hand, which means you may have to compromise.

In this article, we aim to cover boiler selection for domestic property as well as for commercial premises. First let’s consider your specific needs:

What size environment are you looking to heat?


As mentioned above the diverse range of boilers to select from can be overwhelming. So, before you dip into the budget, let’s first consider a few things.


Domestic Heating: What is the size of your property? Take into consideration the number of rooms inhabited that require heating. Also, if you’re planning an extension to the property don’t forget to include those extra rooms, bathrooms, WC’s or utility room. Remember, not every room may require heating i.e., the utility room for example.

One thing you do want is to have balanced heat to every room inhabited. Does size matter? Well, yes it does because the last thing you want is an undersized boiler that’s unable to adequately heat your home or supply it with enough hot water!

That’s where serviceteam’s qualified gas engineers come in, to accurately scope your property’s size and make recommendations as to the best sized boiler to meet your heating and hot water needs. It’s always best to call serviceteam, rather than taking a gamble or guessing what boiler is best for your property. Afterall, what if you make a wrong decision?

Commercial Heating: First assess your needs, do you want both heating and hot water for your business/commercial premises? Is the area to be heated small in size or somewhere between medium to large like a supermarket, where employees work?

Premises that fall into the above categories could be – Schools, Hotels, Leisure Centres, Spas, Hospitals, Retail, Passenger-Train or Bus Stations, Sports Venues or even Farm buildings.

Let’s not forget either the importance of energy efficiency when selecting a commercial boiler or the potential impact on the environment.

Also, consider the running/maintenance cost and how readily available are replacement parts and how good is the after sales service? If the premises is large and divided into sections you may need to consider zone controls in areas where heating is not constantly needed?

A Commercial boiler is heavy duty — unlike domestic boilers which are much lighter by comparison. A commercial boiler is sturdy in design and can withstand high stress on a regular/continuous basis.

KW Output Power?

A simple guide – if your property has many radiators and many tap outlets, the higher the KW boiler rating is better as it will be able to cope with high demand at any given time. When you are trawling through the boiler market you will frequently come across the term KW. It gives an indication of how powerful the boiler will be.

Having a high boiler KW rating in a small property could mean wasting energy and increasing your energy bills. Likewise, a low KW in a large property won’t meet your heating and hot water demands.

KW (kilowatt) = Power Required.
KWh (kilowatt – hour) = the energy needed for continuous power.

So, when choosing a new boiler it’s worth considering the property and family size. How many rooms are occupied and need to be heated? Is it a Victorian or Georgian property or a more modern one? How often do family members shower/bath/wash etc. If the family is large (as in numbers) It may mean the KW is on the limit (42-50 KW-ish) for a domestic boiler.

As a rough guide, a 24-25KW boiler in terraced houses or apartments with up to 10 radiators would be adequate. A large property as above (Victorian/Georgian) with approx 20 radiators would need a KW output of (ITRO) 40KW. So, size does matter as well as the family size and hot water/heating needs.


You are governed by property and family size regarding heating and hot water requirements.

What Boiler best suits your needs?

There are 3 boiler types to choose from: Heat-only boilers, combi boilers and system boilers.

Let’s explore each of these boilers in turn.

Heat-only Boiler (Regular Boilers)

Often referred to as ‘conventional boilers’, traditional boilers or open-vent boilers. The mains water supply fills the main cold water tank. The water is then directed to the hot water cylinder, which the heat exchanger inside your boiler heats up and distributes the heated water to showers, radiators and taps.

They are dependent on 2 Tanks: the Boiler and the Hot water storage cylinder. These are also known as the expansion tank and feed tank. Heat-only Boilers are more suited for large properties.

Specifically, they are better able to meet the demands of heating as well as numerous taps and shower heads. A heat only boiler could be the ideal partner to manage your hot water demands. Whereas, a combi would find it difficult to keep up with demand.

Combi Boilers

A Combination or combi boiler is a convenient space saver especially if space is at a premium in your property. They provide hot water and heating, on-demand (no waiting for the water to heat up when running the tap). They are able to switch between either water or Heat (or vice versa).
When space is limited combi boilers are the best choice i.e., in small terraced houses, flats, apartments, bed sides. There’s a downside however, if the boiler packs up there is’t a water storage facility, therefore, no hot water or heating until the boiler is fixed!

System Boiler

System boilers don’t require a header tank tucked away in the loft, it saves some space and dispenses with any repairs/maintenance. There are no open vents and the system gets its water supply directly from the mains. If a leak occurs in the system it can be easily identified via a drop in the gauge pressure.

As far as the tanking arrangement goes, there’s no storage tank, no expansion tank and no external expansion-vessel, in fact it’s tank free! The only requirement is a cylinder to store hot water.

WHICH? Will help you choose a reputable boiler brand

It might be time consuming but in the long run doing effective research will help you make the right boiler selection based on the above criterion and hopefully, prevent you from making any knee jerk decisions!

Warranty/guarantee is an important feature for any newly purchased product and boilers are no different. Check out the warranty offered by your selected boiler manufacturer. Does it cover ‘parts and labour’ within the guarantee period? Remember, when the new boiler has been installed it must undergo an annual boiler service (ABS) or risk voiding the warranty/guarantee.

A premium manufacturer can typically offer extended warranties, which will protect you from labour and replacement part/s costs. If a breakdown occurs your first port of call is with the installer.

They will run through a checklist with you to ensure the fault is not user-error and detect if the fault is with the boiler. They will contact the manufacturer on your behalf and request to contact you to arrange a call-out at your convenience.

Some improvements in boiler technology (weather compensation)

Just recently energy costs have reached unprecedented levels as never experienced before. So, it makes sense to manage energy consumption like never before!

Technology has been developed to do just that. Currently, when the CH timer has been manually set and the heating is turned on, it is governed by the settings selected and will only turn off when the timer comes to the end of its cycle. That means you could be using costly energy unnecessarily if temperatures rise.

With Weather Compensation technology, the electronic controller (in the heating system) can proactively detect and adjust the heat supply (up or down) without your help. When the weather conditions outside change, it should automatically apply changes which can give savings on your energy costs and it is certainly worth exploring.