Boiler buying guide

When looking for a boiler to buy, you should consider several factors.

  • The size of your household.
  • How you intend to use the boiler.
  • The size you need and the space you have available.
  • The make of boiler you prefer.
  • Your budget.

Boiler Efficiency

Boilers can contribute up to 60% of the CO2 emissions in homes so it’s important to choose an efficient boiler. Choosing the right boiler can not only reduce your carbon output but can also cut down your energy bills. Modern boilers are much more efficient than older boilers with non-condensing systems. By replacing an older boiler with an up to date model you can improve your boiler efficiency by up to a third.

The key to getting the best boiler is to buy one which is in the right size and type for your property.

Getting the Right Size Boiler

What size boiler do you need?

The three key factors for determining the size of boiler you need are:

  • Your preferred boiler’s heating and hot water ability.
  • How much space you have available.
  • How many bathrooms you have in your home, and how many people live there.

Keep the above in mind, however, you can also consult a heating engineer to guide you in the right direction.

Gas Boilers

If you are connected to a gas heating system that has a gas boiler, you can choose between a Combi boiler and a heat-only boiler. A Combi boiler supplies heat for your homes water needs and your radiators. A heat-only boiler has a cylinder for hot water storage that is fed by a cold water tank. There is also a system boiler that is similar to a heat-only boiler but without the provision of a cold water tank.

How to Save Money by Purchasing an Efficient Boiler

If you already have a boiler, you need to check its efficiency rating.

A new financed boiler is A-rated which basically means that its efficiency is over 90% whereas an old boiler could even reach the G-rating level meaning its efficiency is below 60%.

If you live in a 4 bedroom detached house and have a G-rated boiler, you could actually save around £305 annually (£25 per month) which is more than it would cost you to get a new financed boiler.

The average cost of a new boiler depends on the size and brand but is usually between £500 and £2,500.

How Much Will it Cost to Install a Boiler

The table below compares the key features of the best boiler brands:

BrandBoiler typesFuel typesWarranty rangePrice rangeTrustpilot Score
Grant CombiRegularSystem Oil2 to 5 years£1,250 – £3,1009.4/10
Ideal CombiRegularSystem Gas2 to 5 years£700 – £4,5008.5/10
Vaillant CombiRegularSystem Gas2 to 5 years£750 – £2,5008.9/10
Viessmann CombiRegularSystem GasOil 2 to 5 years£840 – £2,9009/10
Worcester Bosch CombiRegularSystem GasOil 2 to 6 years£800 – £2,3509.1/10

How much it costs to install a boiler depends on the number of rooms in your house and number of people living there
Source: https://www.theecoexperts.co.uk

Key Features of a Boiler

Condensing vs. Non-Condensing

A condensing boiler uses the water vapour produced during the heating process, and recycles wasted energy to heat cold water in advance. These types of boilers are energy efficient as they are able to provide sufficient heat even under low temperatures.

Non-condensing boilers function at high temperatures where heat is lost outside the premises. They have an efficiency of between 80-88% whereas condensing boilers have an efficiency of more than 88%.

Sealed vs. Non-Sealed Combustion

A boiler either has a sealed or non-sealed combustion unit. However, one with a sealed combustion unit is better as it fetches air from the outside into the burner and removes exhaust gases out of the house. In addition, sealed combustion boilers do not bring dangerous gases inside the house. Non-sealed boilers bring heated air in and direct it up in the chimney, wasting energy by heating the air.

Other Factors to Consider Before Buying a Boiler


If your home is in a place with a warm climate, you most likely do not require a central heating system. If you live in a colder climate a central heating system will definitely be needed, so a boiler would be ideal for you. If you are situated somewhere warm then you should consider buying a heat pump which will cater for both your air conditioning requirements and modest heating needs, such as heating bath water.

Type of Fuel

Boilers that use gas are cheaper to operate than those that use oil. However, the type of fuel you choose will also depend on what is available where you live.


Boilers are only for the provision of heat. This means that a cooling system will also be necessary if you need to air condition your house.

How to Boost the Efficiency of your Boiler

Before you buy a boiler, you should make your home energy efficient by reducing the heating load. This will enable you buy a smaller and cheaper system. It also helps to have smart thermostats so you can easily control the temperature in your home, read more in our guide to smart thermostats.

Top Tips to Make Your Home Energy Efficient

  • Insulate your walls and attic.
  • Put weather stripping on doors and caulk on windows to prevent heat from escaping.
  • Insulate ducts on the cooling system in attics and crawl spaces.
  • Regularly clean the chimney.
  • Ensure all fans are set to a clockwise motion to keep heated air down.
  • Install automatic thermostats to reduce temperatures during the night and when there’s no one in the house.

Once you’ve bought your new boiler you should have it serviced at least once a year. They will be able to ensure your boiler is functioning properly which will keep maintenance costs low and keep you and your family safe. Find our more about our boiler servicing options.

Check out our other boiler buying guide to understand the most important factors you need to consider when looking to buy a new boiler. Our guides include an electric boiler buying guide and combi boiler guide.