Keston Combi Boiler

The compact Keston Combi Boiler comes in two different outputs and can be sited almost anywhere in the home.

Otherwise known as the C30 and C35, Keston’s combi boilers are compact appliances that ensure maximum comfort and efficiency. Although set up to use energy from natural gas, these boilers can be converted to LPG with a special conversion kit, making them perfect for homes that are either on or off the gas grid. They also feature weather compensation as standard and help you to make big savings on those energy bills.

How Much Does this Boiler Cost?

The Keston combi boiler series includes two models with different outputs of 30kW (the C30) and 35kW (the C35) and hot water flow rates of 12.4 litres and 14.5 litres per minute respectively. Prices vary according to the outputs and typically range between £1,190 and £1,300. This does not, however, include the cost of fitting the boiler, so you’ll need to shop around to find the most competitive quote on both the boiler and installation.

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How will I know if this Boiler is Suitable for My Home?

Like all combi boilers, the Keston C30 and C35 combi boilers do not require a separate tank or cylinder. Of course, this is great news if you don’t have enough space to house extra water tanks. We should also mention that both the C30 and C35 are small enough to fit inside a standard kitchen cupboard. As they have high heat outputs and excellent hot water flow rates, they are best suited to medium and large-sized homes.  

We recommend you ask a Gas Safe registered engineer to take a look at your home and assess your unique requirements before making a final decision. The Keston Combi series includes two options, so you’ll also need to ask your engineer to help you choose the correct heat output and flow rate for your home and needs.

Is it a High Efficiency Boiler?

Yes. The Keston Combi is A-rated for efficiency so it will provide excellent energy savings. Both options in the range are fully modulating and supplied with weather compensation, making them Boiler Plus compliant as standard. If you currently own an old boiler and go on to replace it with a Keston Combi, you should save a fair bit of money on your annual energy bills and lower your carbon footprint at the same time. 

Does this Boiler have a Good Range of Controls and Features?

Keston has included all sorts of decent controls and features, such as a large backlit display with user-friendly controls and an easy to see pressure gauge. You also get inbuilt frost protection and a pre-fitted filling loop, along with a 50mm muPVC solvent weld flue that allows for simple installation. Plus, the boiler can be installed up to 27 metres from the flue outlet when connected to Keston’s Twin Flue system. Not forgetting the weather compensator, which helps to make sure your home is comfortable all year round.  

How long is the Warranty on this Boiler?

The Keston Combi comes with a 5-year parts and labour warranty as standard, but this can be extended to 7 years if you choose to have your boiler installed with a Keston filter. The offer to upgrade the warranty is only available until the 31st of December 2019.

Summary of Important Information

  • Priced between £1,190 and £1,300
  • Heating output of 30kW or 35kW
  • Hot water flow rate of 12.4 litres or 14.5 litres per minute
  • Dimensions of 700mm (H) x 395mm (W) x 278mm (D)
  • Uses gas or LPG as its fuel source
  • A-rated for efficiency
  • 5-year warranty as standard

Pros and Cons

Although the Keston Combi has lots of pros, it seems as though Keston Boilers has a ‘poor’ Trustpilot rating, with owners saying they have experienced problems with their appliances. That’s not good to hear, so bear this in mind when shopping around and comparing boiler brands.


  • Fits in a kitchen cupboard
  • Suited to medium and large-sized homes
  • No need for separate cylinder or loft tanks
  • Easy to install, use and service
  • Frost protection – protects boiler when installed in a garage or basement
  • Weather compensation supplied as standard
  • Provides maximum energy efficiency – reduce fuel bills and carbon emissions
  • Compatible with a range of Keston controls – improves efficiency and performance
  • Works with LPG if required  – perfect for properties off the gas grid  
  • 5-year warranty
  • A limited-time offer of a 7-year warranty upgrade with a Keston filter


  • Keston has a ‘poor’ Trustpilot rating – correct at the time of writing in May 2019

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