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22 June 2021

Five things to know before buying a new boiler

Buying a new boiler is a big and expensive decision. Here are five things you should know before you get a new boiler.
Matthew Knight

Buying a new boiler is an expensive and complicated process at the best of times - let alone against the backdrop of your old boiler breaking down suddenly in winter. 

With a typical boiler installation costing anywhere between £3,000 and £5,000, here are five things you need to know before you sign on the dotted line for your new boiler. 

Read our boiler reviews to make sure you buy a brand you can trust.

Video: how to buy the best boiler

1. The importance of a reliable new boiler

It's simple really - the more reliable your new boiler, the less money you will have to shell out on expensive repairs. According to our annual boilers survey, the average cost of a boiler repair is £210 - which is quite an incentive to pick a reliable brand.

If you choose the most reliable brand of boiler, according to our survey, an impressive 63% are likely to still be fault free after six and a half years. Get unlucky and pick the least reliable brand, and this falls to a disappointing 45%.

Don't be left with cold showers in a freezing cold home - only pick a new boiler from one of the most reliable and best boiler brands

2. Get your boiler engineer's opinion - but consider their answer carefully

Your boiler engineer will be an invaluable source of information during the buying process. He or she will be able to guide you to make the best choice on the type and size of boiler you need. 

However, what many people are not aware of is that many heating engineers are incentivised to install particular brands of boilers and some will only install boilers from particular brands. 

What this means is that if you are relying on your heating engineer to recommend a good reliable brand, you can't be sure they are just recommending a brand that benefits them rather than you. You also can't be sure their recommendation reflects the opinion of the majority of other heating engineers, or the reality of how reliable boilers are in people's homes. 

See the best and worst boiler brands which include the verdicts of 171 Which? Trusted Trader-endorsed heating engineers.

3. What types of boiler are there?

There are three main types of gas condensing boiler to choose from: a combi, system and conventional. 

  • A combination boiler, commonly known as a combi boiler, heats water as you need it and eliminates the need for a storage tank.
  • A heat-only boiler, sometimes known as a conventional boiler, means you will have a hot water tank or cylinder where hot water can be stored for later use. 
  • A system boiler is just like a heat-only boiler, but more components are built in. This can make system boilers easier to install than conventional ones and they tend to take up less space.

If you live in a small home with only one bathroom, or live on your own or with only one other person, a standard combi boiler without a hot water tank will usually be the best choice. If you know it's a combi boiler you need, take a look at the best combi boiler brands

If your home is larger or there are more than two people living in it, then a heat-only or system boiler is usually a better option. 

Your heating engineer will be able to talk you through the different types of boiler and make a recommendation for the best choice in your home. 

4. Choosing an efficient new boiler

If you are replacing an old-style boiler with a modern gas condensing boiler, the good news is you are likely to save a decent amount on your energy bill. 

The latest savings estimates (source: Sedbuk) suggest that if you live in a detached home and are replacing an old-style heavyweight boiler with a modern condensing boiler, you will be swapping average fuel bills of £1,705 for £1,053 - a £652 saving.

If you already have a modern condensing boiler and are simply looking for a replacement, the good news is that they are all very energy efficient.

Based on analysing all the gas condensing boilers available in the ranges of the biggest 11 manufacturers in the UK, which is more than 300 boilers in total, the difference in efficiency is minor. 

Based on the efficiency calculated to an industry standard called SAP 2009, the least efficient has a rating of 88.2 and the most efficient is 91.0. The average efficiency of all the boilers analysed is 89.2. 

In our boiler reviews we reveal the efficiency of every single boiler, along with key information on the reliability of each brand of boiler. Plus all the important specification information you will need to select the best boiler for your home. 

5. What size boiler do I need?

When picking the best size boiler for your home you should consider two things: 

  • The heating and hot water capabilities of the boiler 
  • The physical size of your boiler and whether it will fit in the space you have it destined for.

The correct heating size of the boiler will be something unique to you and your home, as it depends on things such as how many bathrooms you have and how many people you live with. This is something your heating engineer can help you with, and he or she will be really key to making sure you achieve your hot water and heating requirements.

In our boiler reviews we display 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. 

It is always good practice to ask your heating engineer what size boiler he or she thinks best fits your requirements. 

For more information on accurately sizing your new boiler, head to our guide on how to buy the best boiler.

If you're looking for a heating engineer you can rely on, use Which? Trusted Traders to find a local and fully vetted installer in your area. Use our search tool below to find a reliable local tradesman in your area.