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A new boiler is likely to be one of the most expensive household purchases you'll make – usually when your current one breaks down and needs replacing quickly.
So it's important to take a moment and make sure you get the right one for your home, from a brand you can rely on. Read on for our expert advice on buying the best boiler for your home.
Already know what type of boiler you need? Head straight to our boiler reviews.
With the average price of a single repair costing about £200 (Which? boiler survey, 2022), getting a boiler from a reliable brand will cost you less to maintain over the years.
We ask boiler owners how satisfied they are with their boiler, and if they would recommend it to a friend. We also survey 196 Which? Trusted Trader heating engineers to get their expert opinion on each boiler brand. These are then combined to create a boiler brand's overall score.
Become a Which? member to unlock the tables below and discover the best boiler brands.
Tables last updated September 14 2022.
When buying a new boiler, you need to consider what type of boiler you want, what size of boiler you need, whether your heating system needs anything doing to it while you're installing a new boiler, and which brand of boiler will be most reliable.
Watch our video to help you decide which type of boiler is right for you.
Not sure if you need a new boiler? Look out for these five signs you need a new boiler.
Most UK households are connected to the UK's gas network and so have a gas heating system equipped with a gas boiler.
But for the 15% of homes not on the gas network (Energy Savings Trust, May 2021), there are alternatives such as fitting an oil boiler, liquid petroleum gas (LPG) boiler, or a wood-burning stove with a back boiler (which come with another set of environmental implications).
There are typically three different types of gas boiler to choose from: combination (combi) boilers, heat-only (also called conventional or regular) boilers and system boilers.
Your heating engineer will be able to talk you through the different types of boiler and make a recommendation on the best type for your needs.
Learn more about boiler pros and cons in our different types of boiler advice guide.
The 2021 Heat and Buildings Strategy from the Department of Business, Energy and Industrial Strategy reported 77.1 mega tonnes of green house gas emissions from UK homes – that's around 2,666kg per home on average. In total, heating our homes accounts for around 17% of UK carbon emissions.
The UK is heading towards net zero carbon emissions by 2050. To achieve this household emissions will need to be reduced by 95%, to just 138kg a year per household by 2050 (Energy Savings Trust, 2021).
Since 2018, the government's 'Boiler Plus' legislation has required that all newly installed boilers have a minimum ErP efficiency of 92%, plus time and temperature controls fitted.
But a boiler's efficiency depends on how it's working in your home. A boiler won't achieve its efficiency potential without compensation controls that adjust its flow temperature automatically.
Learn more about boiler efficiency in our guide to which boilers are most energy efficient.
In order to reach the UK's net zero target by 2050, we will all need to eventually install low-carbon heating systems. Many are available to install now, with schemes designed to financially reward people who use renewable energy to heat their homes.
You can learn more about low-carbon heating, including how it works, the costs and if it's suitable for your home, in our expert guides on:
You can still reduce your carbon footprint and heating bills with a gas or oil boiler. Discover our top tips to reduce your heating bills.
Choosing the right boiler size includes two things: its physical size (whether it will fit in the space you have designated for it) and its heating/hot water capabilities. The latter is measured in kilowatts (kW) and is often just referred to as 'boiler size'.
The correct boiler size will be something unique to you and your home, as it depends on many things: how many bathrooms do you have? How many people do you live with? Do you have large gatherings at your home? How many radiators do you have?
However, the general rule is the more heat and hot water you need, the higher a kW boiler you will need.
Choosing the right size of boiler is something your heating engineer can help you with, and they will be key to making sure you achieve your hot water and heating requirements.
We give each boiler's hot water and heating capabilities and give an indication as to what type of home it's suitable for. We also display the boiler's measurements, so that you can figure out if it will fit in the space you have for it.
In the tables below you can see which is the right size boiler for you, according to the Heating Hub that provide independent and expert advice on heating systems1.
It's always good practice to ask your heating engineer what size boiler they think best fits your requirements. Use the search tool below to find a local expert Which? Trusted Trader
Reliability is by far the most important factor that will influence which boiler you'll buy. So we go to great lengths each year to separate the good from the bad brands in terms of reliability.
In 2022, we surveyed 9,722 people who bought a boiler in the last six years and asked what year their boiler first developed a fault (if at all). From this we calculate how many boilers remain fault-free over the first six years.
As you can see in the graph above, there's a big difference between the best and worst brands. After six years, you're almost twice as likely to have experienced a fault with the worst brand than the best.
If you live in a small flat with only one bathroom, then a combi boiler is the ideal choice for you. Combi boilers don't need space for a hot water cylinder to store the hot water, or a large cold water feed tank, which means the boiler doesn't eat away at limited space.
We would recommend a small combi boiler that has an output of less than 24kW. Make sure you buy the best by selecting from one of our Best Buy small combi boilers.
How to get a free boiler or grant – find out if you're eligible.
For a mid-sized family home, the choice will be between a mid-sized combi boiler or a small heat-only boiler. If you have multiple bathrooms and a large family, with room to store a hot water cylinder and cold water storage tank, then the benefits of a heat-only boiler may start to outweigh the benefits of a combi.
For a larger home, the best choice is likely to be a heat-only boiler. You will need space for a hot water storage cylinder and a cold water feed tank in the loft, but for a larger home with multiple bathrooms, a heat-only boiler is nearly always the best option.
Depending on the size of the home and how well insulated it is, you will need either a small or mid-sized heat-only boiler.
If you live in an area with low water pressure, or if you live in a large home where you've converted the loft and don't have space for a cold water feed tank, then a system boiler could be your saving grace.
System boilers don't require a cold water feed tank and they also make use of a pressurised system, which makes low mains water pressure much less of an issue.
Make sure you pick one of the very best brands by heading to our system boiler reviews.
Keep your boiler in tip-top condition by getting the best boiler service.
However, even though you won't be the one physically installing the boiler, there are still big decisions that need to be made.
Read on to find out what you need to ask and tell your engineer when they visit to give you a quote, what you should expect from a proper boiler installation quote, and checks you can carry out after the new boiler is installed.
When you get a heating engineer to assess your home and give you a quotation for a new boiler, it shouldn't be a quick conversation. A good installer should take the time to conduct a full survey of your home, learn about your heating and hot water requirements, and only then give you recommendation on the boiler type and brand for your home.
In order to get the best advice and quote, here are six questions to think about before you have a conversation with your installer:
We think a good installer will mention some or all of the following below. If they don't come up, ask them yourself.
New boiler installation costs can typically be anywhere from around £1,400 to £7,000, so we recommend getting at least three quotes to ensure you're getting the best deal. Don't be taken in by any headline discounts, look at the total price for the boiler and labour charges.
You may find that some installation companies will suggest a replacement boiler for you rather than allowing you to choose your preferred model. This is because many heating engineers are incentivised to install particular brands.
So it's vital that you check your heating engineer's recommendation against the views of their peers – which is where we can help. We surveyed 153 Which? Trusted Trader heating engineers in June 2021, to find out what they really think of the different boiler brands on the market. Read our boiler brand reviews to find out what they said.
The UK government introduced new legislation in 2017 called 'Boiler Plus' to govern new gas boiler installations. Since 2018, the regulation requires that all new gas boiler installations in England:
This is all to make gas boilers as efficient as possible, reducing their environmental impact, and saving you money on your heating bills.
Heating controls also let you take charge of when, where and at what temperature your heating is operating. It’s a good way of managing your heating costs, as you can ensure that your heating is only on certain rooms at certain times. Read more about boiler controls and thermostats in our expert guide.
Here is what you should look for in a correctly itemised installation quote:
After installation, your engineer should complete a series of safety and performance checks to make sure your new boiler is working correctly.
The results should be recorded in the back of the boiler's instruction manual; this forms part of the benchmark process that's important for the warranty on your new boiler. You should also make sure your engineer registers your boiler with the manufacturer to activate the warranty.
If, after these checks, you notice cold spots on your radiators or they are taking a long time to heat up, this could be a sign that your system hasn't been balanced or cleaned properly. You should contact the installer immediately.
Ready to get a new boiler installed? Read our expert guide on how much a new boiler costs.
Getting the best boiler installation depends a lot on the installer you choose for the job, so pick a Which? Trusted Trader, all of whom have passed our stringent standards to become accredited.
To replace a gas boiler, the installer must be Gas Safe registered, so ask to see a registration card, or check the Gas Safe Register.
You can also take steps to ensure you are getting what you want and need from your new boiler installation – for example, it's always good practice to ask your heating engineer what size boiler they think best fits your requirements, rather than trying to work this out yourself.
Choose a Which? Trusted Trader for an unbiased, expert opinion.