Find your new energy-efficient system boiler

A new system boiler from British Gas could improve your home's energy efficiency - and lower your gas bill by up to 22%.

Get a new system boiler

How to get your system boiler quote

Just book a home visit with one of our experts. We'll give you a quote that covers everything you need for installing your new system boiler, including moving it to a new location and any pipework.

Book a free home visit

Pick a time that's best for you to get an expert to visit your home and help you find your next system boiler.

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What is a system boiler and how do they work?

What is a system boiler?

Like conventional boilers, system boilers need a hot water cylinder. However, unlike conventional boilers, they don’t need a cold water tank, and components like pumps and valves that are separate in conventional boilers are built-in with a system boiler. You might also hear system boilers being called ‘closed vent’ or ‘system sealed’ boilers.

How do system boilers work?

System boilers work in the same way as conventional boilers, it’s just the components are slightly different. Think of them as the modern upgrade to a conventional boiler.

  • Cold water from the mains water supply enters the system boiler
  • It passes over a heat exchanger, which heats up the water
  • Once it reaches the temperature you’ve set on your thermostat, a pump moves the warm water to your radiators
  • The hot water stored in the cylinder stays there until it’s needed
  • When you turn on your taps or showers, the hot water is pushed out from the cylinder.

What is the difference between system and heat only boilers?

System boilers work in a similar way to conventional or heat-only boilers, except a conventional boiler needs a cold water tank. Heat only boilers can maintain the water pressure using a feed and expansion tank, whereas a system boiler relies on the mains pressure – so if you live in a low water pressure area, then a system boiler may not be right for you.

Are system boilers expensive to run?

If you have a regular routine for using hot water and know how much you’ll need and when, then a system boiler set to your schedule may actually be more cost-effective than other types of boilers. That’s because you’re paying to heat up only the water you need, and then not wasting it.

Spread the cost of your system boiler

Pay monthly

Get up to 3 years' interest-free credit with £0 deposit (0% APR).


Pay in full

Secure with a 10% deposit and pay the balance after your system boiler is installed.

Simple ways to get your system boiler quote

Whatever you choose, we’ll give you personalised system boiler recommendations tailored to your home.

Home visit

Best if you’d like to chat to an expert at home – or want to change your boiler type or location.

Book a home visit

Online estimate

Want your new system boiler in the same place as your existing one? Go online for a quick quote.

Get started

Do system boilers work best in smaller or larger houses?

System boilers are suitable for a variety of homes but work best in larger homes. As long as you’re got the space for a hot water cylinder, you can get a system boiler installed. System boilers are space-saving compared to conventional boilers, which need a cold-water tank in the loft.

Is a system boiler right for me?

Not sure where to start when it comes to buying a system boiler? It’s understandable. So here’s a rundown of the pros and cons.

Pros of system boilers:

  • Easy to install and repair
  • Energy-efficient so could help you spend less on heating your home
  • Supply hot water and heating at the same time
  • No need for a water tank in the loft

Cons of system boilers:

  • Can be quite large and take up more space than other boiler types
  • Hot water needs to be heated up in advance – it’s not available instantly
  • A limited supply of hot water – once it’s gone, you’ll need to wait while it heats more



Space saving – as many of the components are integrated,
and it doesn’t need a cold water tank, system boilers don’t take
up as much room as a conventional boiler

Pressure problems – as with combi boilers functionality
depends on mains pressure, so they won’t work as well if you
have poor flow rates or incoming water pressure

Less worry – there are no components in the attic, so you
don’t need to fret about potential leaks or freezing in the winter

Quicker install – there are fewer pieces to fit, so it can be
installed quicker than a conventional boiler

Why choose British Gas for your new system boiler?

We install more boilers than anyone else - so when you get your system boiler from British Gas, you know you're in safe hands.

  • Over 200 years of experience

    And trusted in millions of homes across the UK

  • 6,500 expert

    So we’re always ready to install your new boiler

  • Up to 3 years' interest-free credit

    Spread the cost with £0 deposit and no hidden fees

  • Up to 12 years' warranty

    So if anything goes wrong. we’ll get it sorted

We stock the best new system boiler brands

At British Gas, we partner with top system boiler brands, including Valliant, Worcester and many more. And we’ll give you impartial advice to help find the best system boiler for your home.

What our customers think of us on Trustpilot

I'm so pleased i chose British Gas to install my boiler. The engineer was professional, efficient and very helpful!


Trustpilot 5 stars

Absolutely amazing service - our boiler broke down and new one was ordered and delivered ready for install the next day. Thank you so much!


Trustpilot 5 stars

Very fast and efficient service from British Gas when we had them install a new boiler. It was fitted within weeks and the house and garden where the soakaway was fitted were left spotless too.


Trustpilot 5 stars

Frequently Asked Questions

Are system boilers efficient?

All the system boilers we sell at British Gas are A-rated for efficiency. And in general, system boilers are known to have an efficiency rating of 94%, which makes them great for using the majority of its fuel and turning it into heat and hot water for your home, without wasting too much energy.

Do system boilers have a pump?

Yes, it’s what sends hot water around your home. There’s a water pump within system boilers and when you turn the boiler on, the pump quickly delivers hot water to your radiators and taps.