Which is the Best 28kW System Boiler?

Which is the Best 28kW System Boiler?

Properties with a higher demand for central heating and hot water that aren’t suited to a combi boiler, will be best off with a system boiler.

A 28kW system boiler is perfect for a semi-detached home with 3 bedrooms, 2 bathrooms and around 10 radiators. Here are 3 of the best 28kW system boilers you’ll want to consider:

  1. Baxi 800
  2. Navien NCB
  3. Potterton Gold

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Is a 28kW system boiler suitable for my home?

When a combi boiler simply won’t do, a 27 kW system boiler is a great alternative. They’ll be able to supply central heating to around 10 radiators and deliver domestic hot water at a high pressure to more than 1 tap or shower at a time. So, if you have 2-3 bathrooms and live in a semi-detached home, a system boiler is worth considering.

However, unlike a combi boiler, system boilers will need to be installed as part of a heating system that also includes a hot water cylinder.

To find out the best idea of the ideal output rating for your home, you should hire a Gas Safe registered engineer. With Boiler Guide, you can get free quotes from heating engineers based in your area, who will take a look around your property and provide you with a comprehensive quote, let you know exactly the type of heating system you need and answer any questions.

Best 28kW system boilers

Best 28kW System Boilers Seasonal Space Heating Efficiency ErP Rating Warranty
Baxi Megaflo 88.5% A 7 years
Navien NCB 93% A 7 years
Potterton Gold 91.2% A 2 years

Baxi Megaflo

Baxi have built up a great reputation for their boilers with both heating engineers and homeowners. Their Megaflo range of system boilers are highly efficient, are made of quality brass components and are covered by an extensive 7 year warranty.

  • Frost protection for units installed in garages and lofts
  • Front access which speeds up servicing and potentially lower costs
  • A range of flue options for flexible installation
  • Compatible with the Megaflo Eco cylinder – an industry-leading hot water cylinder
  • Endorsed by the Energy Saving Trust

The Baxi Megaflo range of system boilers includes a number of different outputs, including 15 kW, 18 kW, 24 kW and 32 kW.

Navien NCB

Navien are a more recent addition to the UK boiler market than the other manufacturers and they’ve quickly become a manufacturer worth considering. The Navien NCB 28 kW system boiler is highly efficient, boasts high-quality components and comes with a lengthy 7 year warranty.

  • Stainless steel heat exchanger for increased efficiency and extended boiler lifetime
  • A lengthy flue makes installation more flexible to give you greater chance of where to have the unit installed
  • A blue touchscreen display offers you greater control while also showing clear messages about the status and efficient running of the unit
  • OpenTherm ready which can help to lower the installation costs

The NCB System range also includes output ratings of 20 kW, 23 kW and 33 kW.

Potterton Gold

Potterton are part of the Baxi Group so while they aren’t one of the leading or most well known manufacturers, they have the backing and technology of one.

  • A range of flue lengths up to 20 metres offers great choice with where to have the boiler installed
  • As a full-modulating unit it’s designed to run more efficiently
  • A pre-plumbing jig helps to speed up the installation process
  • Energy Saving Trust endorsed

Lower outputs of 18 kW and 24 kW are also available in the Potterton Gold range of system boilers.


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How much do 28kW system boilers cost?

A system boiler can typically cost between £500 – £3,500 before installation with our list of the best 28 kW system boilers ranging from around £635 up to £1,030.

Best 28kW System Boilers Potential Cost (before installation)
Baxi Megaflo £870 – £1,030
Navien NCB £995
Potterton Gold £700 – £750

In addition to the system boiler, you will also need a hot water cylinder to store the hot water. Unvented cylinders are widely recommended by heating engineers as they offer much more flexible installation over traditional vented cylinders – find out the Best Unvented Cylinders.

Best 28kW system boilers for off-grid properties

All of these system boilers run on natural gas which means that your property will have to be connected to the gas network. However, this doesn’t mean that if you live off-grid then you can’t enjoy the benefits of the best 28 kW system boilers as some run on LPG – a gas that can be stored onsite.

Best 28kW System Boilers LPG Compatible?
Baxi Megaflo No
Navien NCB Yes
Potterton Gold Yes

LPG isn’t the only option for off-grid homes, there’s also oil. A number of manufacturers offer system boilers that run on oil that are suitable for semi-detached homes, including Firebird, Navien, Viessmann and Worcester Bosch.

Oil System Boilers (28kW – 34kW) Output Rating Efficiency Warranty
Firebird Envirogreen Slimline Systempac C35 35 kW 92.6% 2 years
Navien LCB700 28 kW 93% 10 years
Viessmann Vitirondens 200-T 28kW 97% 10 years
Worcester Bosch Greenstar Danesmoor 32 kW 91% 2 years

How do system boilers work and why install one?

A system boiler sits somewhere in between combi and regular boilers in terms of how they operate. While most of the components are within the unit itself (like a combi) they need a hot water cylinder (like a regular boiler) to store the hot water. However, unlike a regular boiler, there’s no need for a cold water or expansion tank in the loft as they take water directly from the mains. By working in this way, system boilers are able to meet high demand for heating and hot water – which is great news for larger properties.

If a heating engineer recommends having a system boiler installed, then there are a number of benefits:

  • More straightforward installation compared to regular boilers
  • By storing domestic hot water in a cylinder, system boilers are able to meet higher demand for hot water – ideal for large and busy homes
  • Deliver water to taps and showers at a high pressure
  • Thanks to being fitted with a pump they’re able to respond to you turning on the central heating much quicker than older heating systems
  • If you have a solar thermal system (or are considering one) then you can install a solar-compatible cylinder installed to help lower your energy bills

Get free system boiler installation quotes

If the time has come for you to find a new boiler, then finding a fully-qualified local boiler installer has never been easier. You can get free quotes from up to 3 heating engineers based in your area by simply taking a few moments to complete our online form – which involves telling us about the work you need carrying out.

With your quotes in hand, you can be confident that you’re getting the most competitive price for the installation of your new boiler.


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