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Biasi vs Keston: A Boiler Comparison

Rob Wells
By: Rob Wells
Updated: 7th January 2022

Last Updated: 7th January 2022

Biasi vs Keston
Biasi and Keston might not be the most well known boiler manufacturers, but each offer reliable and efficient ranges of combi, regular and system boilers.

For anyone looking for an alternative to the leading brands, Biasi and Keston are great alternatives, but which manufacturer is best?

We've compared the boiler ranges available from each brand in terms of efficiency, warranty and price to help you in your search for a new boiler: Biasi vs Keston.

Biasi vs Keston

Biasi boilers

Biasi are a budget-friendly boiler manufacturer and their boilers also covered by a comprehensive 2-7 year warranty.

They don't have such an extensive offering as leading boiler brands such as Ideal, Vaillant and Worcester Bosch, which might make finding a suitable system tough. However, find a Biasi boiler that suits your home and you'll be investing in a highly efficient unit at an affordable price.

Keston boilers

The latest models from Keston have proved popular and have been well reviewed by homeowners and installers. There are few reports of breakdowns or faults and the installation is made simple by the compact dimensions and low lift weight.

Unfortunately, the twin flue system used by Keston can lead to servicing and repairs becoming fairly costly. Also, the price attached to Keston boilers (£1,000+) might make turning to a leading boiler manufacturer the better option.

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Biasi and Keston boiler ranges

Both brands manufacture a range of combi, regular and system boilers that run on natural gas but LPG versions are available for some models.

Combi boilers

A combi boiler provides instant heating and hot water on demand and, as a result, there's no need to have any cylinders or tanks installed elsewhere around your home.

Biasi and Keston both have combi boiler options, ideal for homes with 1-2 bathrooms, with Biasi offering the wider choice.

Biasi combi range CH output DHW output Efficiency
Advance Plus 7 25c 19.5 kW 26.6 kW 92%
Advance Plus 7 30c 24.4 kW 31.9 kW 92%
Advance Plus 7 35c 29.5 kW 36.4 kW 92%

Biasi combi boilers boast a range of features, including:

  • Stainless steel heat exchanger for increased efficiency
  • Strong flow rate of up to 15.6 litres per minute
  • Compact in size
  • Frost protection
  • LPG convertible

Boiler frost protection is particularly important for boilers installed in garages or areas where the temperature can drop to freezing. With this feature, the boiler will automatically heat up the water within it should the temperature drop to a certain level.

Find out How Boiler Frost Protection Heating Works.

Keston Combi Boiler Range Output Ratings Efficiency
C30 30 kW 94%
C35 35 kW 94%

Keston combi boilers also have a number of benefits, alongside a high output rating, high levels of efficiency and lengthy 7 year warranty:

  • Low lift weight and compact dimensions can reduce the cost of installation
  • Frost protection
  • Weather compensator supplied as standard
  • Few components reduce risk of a fault to ensure reliability
  • Lengthy 7 year warranty
  • Can be converted to LPG for off-grid homes

While both Biasi and Keston have reliable combi boilers on offer, they're not considered amongst the top end units.

Looking for a top of the range combi boiler? Read our guide to Which is the Best Combi Boiler? to find out the best models.

Regular boilers

For large properties with a high demand for heating and hot water, a regular boiler might be the best option as they don't provide instant hot water using the mains water supply. As well as the boiler, regular boilers must be installed as part of a heating system that also includes a cylinder and a feed and expansion tank in the loft.

The clear difference between the regular boilers manufactured by Biasi and Keston are the output ratings. Due to the high output ratings of 45 kW and 55 kW, they're only really suitable for very large properties or small commercial buildings.

Biasi Regular Boiler Range Output Ratings (kW) Efficiency Rating Warranty
Advance OV 15, 18 & 24 92% 5 Years

If you have a dated central heating system in your home then the Biasi Advance OV range has been designed as an efficient, reliable and affordable replacement. The inclusion of a single coil heat exchanger aids water flow to prevent a build-up of debris, greatly reducing the risk of a fault.

The Keston Heat is available in output ratings of 45 and 55 kW, making this range best suited to very large homes (or commercial properties) with a very high demand for heating and hot water.

Keston Regular Boiler Range Output Ratings Seasonal Space Heating Efficiency Rating Warranty Period
Heat 45 & 55 96% 5 Years

For large properties off the gas grid, the Keston Heat range could be an ideal choice as LPG versions are available.

System boilers

If your demand for hot water means having to store hot water in a cylinder then you might want to consider a system boiler.

System boilers have no need for tanks in the loft (like regular boilers) as they take water from the mains but rather than providing hot water instantly, store it in a hot water cylinder.

Biasi have a number of system boilers available to make finding the right unit for your home easier and they're all covered by a warranty of at least 7 years.

Biasi System Boiler Range Output Ratings (kW) Efficiency Rating Warranty
Inovia System ERP 25 92% 5 Years
Advance Plus 7 ERP 25 & 30 92% 7 Years
Advance 25 & 30 92% 5 Years

Biasi system boilers include frost protection as well as being available in LPG form but one of the big selling points is the Inovia System ERP single coil stainless steel heat exchanger. The single coil element increases water flow to reduce blockages forming, which being made out of stainless steel helps to increase efficiency.

Keston only have a single system boiler and it's well worth considering for a number of reasons:

    • Low component count helps to increase reliability
    • Frost protection
    • Twin flue system
    • Low lift weight and compact dimensions to help make installation cheaper
    • Lengthy 7 year warranty available
    • LPG also available
Keston System Boiler Range Output Ratings (kW) Seasonal Space Heating Efficiency Rating Warranty
S30 30 93% 7 Years

You can compare Biasi and Keston boilers using our Comparison Tool.

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In terms of efficiency, there isn't too much to separate any of the boilers from Biasi and Keston – any should help to reduce your energy bills.

To give a better understanding of the seasonal space heating efficiency rating, a boiler that's 92% efficient is only losing 8% of the fuel used (waste gases sent out into the atmosphere through the flue).

So, that means for every £1 you spend on heating your home, only 8p won't contribute to heating your home. This is compared to old inefficient units which could potentially have efficiency ratings as low as 60-70% and equates to potential savings of up to £365* on your annual energy bills.


If you're looking for a budget-friendly boiler then Biasi is definitely the manufacturer to turn to with their units being around half the price of equivalent Keston models in many cases.

A Biasi boiler doesn't even come close to the £1,000 mark, while it's unlikely you'll find a Keston boiler of any type for less than £1,000.

Type of boiler Biasi Potential Cost Keston Potential Cost
Combi £600 – £720 £1,120 – £1,200
Regular £2,100 – £2,600
System £600 – £660+ £1,040+

Don't forget that in addition to the cost of the unit, you will also need to add the installation costs onto that too.

To ensure you get the most competitive price for the installation of your new boiler, we highly recommend comparing quotes from multiple heating engineers. Using Boiler Guide, you can get free quotes from up to 3 Gas Safe registered engineers based in your local area.

Once you've received the quotes, you're free to compare them and hire the engineer you feel is best suited for the job. As well as being completely free, there's no-obligation to accept any of the quotes you receive.


As well as the length of a warranty period, it's also important to compare what's covered by the manufacturer during that time too.

Biasi boilers are covered by a warranty period of 2-7 years and, in the event of a fault caused by the manufacturing process during that time, will repair or replace the boiler.

When the warranty period comes to an end, Biasi off a 'Fix and Forget' service which will see that you're covered for any one-off repairs. This does come at a price of £245 but does include parts and labour.

Keston boilers also come with warranties of up to 7 years, with the standard on all their combi and system boilers being increased to 5 years as of 2018. While the warranty is valid, Keston will see that you're covered free of charge in the event of a mechanical or electrical fault that is the result of poor workmanship.

Read more about Biasi and Keston boiler warranties:

      • Biasi Boiler Warranty
      • Keston Boiler Warranty

Biasi vs Keston: Is there a winner?

If you're not going to turn to one of the leading boiler manufacturers – namely, Ideal, Vaillant or Worcester Bosch – then you're probably hoping for a more cost-effective model. And if that's the case, then a Biasi boiler would be the better option as you could end up spending twice as much on a Keston unit.

While we wouldn't recommend choosing to have a certain boiler installed simply because it's the cheapest, Biasi boilers are still covered by a lengthy warranty period which will see that you're protected.

No matter how much you're spending on your new boiler, you can help to keep the installation costs down by comparing multiple quotes. And that's where Boiler Guide can help.

By taking a few moments to complete our simple online form, you'll get free no-obligation quotes from up to 3 Gas Safe registered engineers who work in your local area.

Need a new boiler?


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*Data Source: Energy Saving Trust, Heating Your Home: Boilers (2022)
Based on replacing an old gas boiler with a condensing A-rated boiler with thermostatic radiator valves, programmer and room thermostat in a detached home. Figures are based on fuel prices as of November 2021.

Rob Wells

About the author

Rob Wells

Rob is another of our resident home heating experts. He manages our external partnerships, making sure you get the most up to date information.

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