When the time comes to replace your boiler and repairing it isn't an option, it's easy to fall into the trap of just buying the cheapest replacement.

But with a little research, you can find the boiler that’s right for you and enjoy lower energy bills. Getting value for money is important but don’t compromise on quality, energy efficiency or capacity.

Following these steps will help you find the right boiler to suit your needs and budget.

Research your options

You’re reading this, so well done on starting your research. You’re on the way to finding your perfect boiler.

The three main types that you’ll find in the UK are combi (combination), conventional and system. Combis are the most popular choice in the UK. If you want to learn more about which of these three boilers might be right for you, we’ve looked at them a little closer. Read Combi, conventional and system boilers: what's the difference? to learn more about the pros and cons of each.

For now though, here’s a quick overview:

Combi (or combination) boilers

80% of boilers sold in the UK are combi boilers. They issue hot water instantly without the need for water tanks or cylinders in cupboards or up in the loft. The units themselves are compact so they can hang on the wall easily.

On the downside, if multiple people in the house need hot water at the same time, water pressure may suffer. So, combis are perfect for smaller homes with one bathroom and kitchen. But if they break, nobody’s going to be happy when there’s no heating or hot water at all.

Conventional boilers

Also known as regular, heat only or open vent boilers. These include a hot water cylinder and a cold-water tank (usually kept up in the loft). They allow more than one person in the house to use hot water at once too, without reducing water pressure. But if the hot water gets used up, you’ll have to wait a little while for more to heat up. Due to the size of the parts needed, they’re therefore not the best option for homes where loft space is a premium.

System boilers

Also referred to as sealed system or closed boilers. These heat water from an expansion tank and store the hot water in a cylinder to be used when needed. They’re smaller than conventional boilers, but still have the downside of a limited supply of hot water. However, they do allow multiple people in the house to use hot water at the same time, so they’re ideal for large families.

Condensing boilers

Combi, conventional and system boilers are also available as condensing boilers. They have the added feature of being able to capture and reuse some of the heat emitted. Because of this, they’re more energy-efficient and reduce carbon dioxide emissions by up to 25%. They’re generally more expensive than traditional boilers but the savings made in energy bills will eventually offset this upfront cost.

Consider what size boiler you need

Knowing what size boiler you need is important if you want the right amount of hot water and heating for your home. Typically, the more heat and hot water you need for your home, the higher the kilowatt (kW) output. Be careful though, as just choosing the boiler with the highest power output may end up costing you more to run and wastes energy too.

To work out the size of boiler that’s best for your home, you need to know the required power output. To get a general idea of that, add up the number of radiators in your home, using the following scores:

For a combi boiler:

  • Up to 10 radiators: 24–27 kW
  • 10 to 15 radiators: 28–34 kW
  • 15 to 20 radiators: 32–40 kW

For conventional or system boiler:

  • Up to 10 radiators: 12–15 kW
  • 10 to 15 radiators: 18–24 kW
  • 15 to 20 radiators: 30–40 kW

Combi boilers use more power as they heat water on demand, rather than slowly circulating hot water around a cylinder as the other two do.

This is only to give you a rough idea of the boiler power requirements you’ll need. A Gas Safe registered engineer will be able to give you a more accurate recommendation. They’ll also consider the size of your home, how well insulated it is, water pressure and other important factors.

Get in touch with the manufacturer

Once you’ve found the right boiler, contact the manufacturer directly to get a list of local installers. Get a few quotes in writing and have an in-depth discussion with each installer to go over your heating needs. A few things to bring up include:

  • How many bathrooms you have in your home
  • How much hot water you typically use
  • Whether you have double-glazed windows
  • How well insulated your home is

This should help you and the engineer decide what capacity your boiler should be.

After you’ve taken some time to chat with your chosen engineer, you should have a good feel for their knowledge and expertise. Boiler installation is a complex process. Check to make sure your engineer is reputable and Gas Safe (previously Corgi) registered. Ask to see their credentials for your own peace of mind too.

Protect your boiler

When all’s said and done, protecting your boiler with an extended warranty makes a lot of sense. You’re covered against breakdowns with a Domestic & General maintenance and support plan. You’ll also get an annual service and ongoing maintenance hints and tips to keep your boiler running.

About the author

Ian Palmer-Smith

Ian is our go-to expert when it comes to plumbing, boilers and carbon monoxide safety. After 39 years (and counting) of working in operations – he knows quite a bit about appliance maintenance and repairs too. Even during washing machine debates (yes, they happen), his expertise is unmatched. Thankfully, Ian regularly contributes to the blog to share his wisdom – helping us all out when our appliances aren’t working quite as we expect.

Last year, Ian was recognised as a finalist in the Institution of Gas Engineers and Managers’ Gas Leadership Award – a real testament to his authority in the industry. He’s even represented Domestic & General at the House of Commons. There he informed everyone about the importance of carbon monoxide safety and awareness in the home.

Outside of work, Ian is usually occupied taking his sons to various sporting events, watching  football, rugby… and a little more sport.

Explore Ian’s wealth of knowledge on all things gas safety and appliance care now. You can check out some of his insightful articles below.

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