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Updated February 2021
If you’re due a boiler replacement, we are here to help you in choosing the best boiler for your specific needs and budget. Doing the hard work for you, our guide to the best boilers in 2021 looks at the best boilers by application.
All modern boilers are now condensing boilers. Condensing boilers can be very similar and this is why every detail counts. To put together this guide, we have looked at the internal components used in each of these and looked at how this translates to quality and long-term efficiency.
To begin, let’s firstly explain the types of boilers available.
Short for combination boiler, this type of boiler doesn’t need an extra storage tank and instead provides heating and hot water directly from one unit. If you have a smaller property with one bathroom, then a combi boiler may be the best option for you. Combi boilers are also usually a more affordable option and are easier to install, which saves you time and money upfront.
If you are new to the world of combi boilers, we’ve created the following easy-to-understand guides which may help:
Whilst these are often also called standard boilers, the technically correct name for this type of boiler is an open vent boiler. Unlike combi boilers, conventional boilers require a cold water tank in the loft and a hot water cylinder elsewhere in the house.
Conventional boilers are most suited to properties with two or more bathrooms and for households which may require hot water from multiple sources simultaneously.
With a system boiler, the heating and hot water components are built into the boiler unit. Whilst hot water is stored in a pressurised unvented cylinder. Unlike a conventional boiler, you don’t need a cold water tank in your loft or attic.
When it comes to boilers, there is no one size fits all. The best boiler for you will depend on a number of factors, these are namely the size of your property and your hot water demands.
In terms of the size of your property, combi boilers are generally suited to smaller properties, whilst conventional and system boilers are better for larger homes.
The most important consideration in your purchasing decision is choosing the right size boiler for your property. The size of the boiler will depend on the size of your house and the number of bathrooms, as this will determine your heating and hot water requirements.
With modern condensing boilers even if you buy a larger capacity boiler, they will modulate energy usage between 5kW and 30kW depending on the load.
However, if you’re moving from a flat to a detached house, your old boiler will not work in your larger new home.
Let’s take a look at the types of boilers suitable for your property type:
If you have a smaller property, say a house with 1-2 bedrooms, or a 1 bedroom flat, with no more than 1 bathroom, which boiler is best?
The simple answer is you don’t need a high capacity boiler.
Whilst you may have a system boiler and do not want to change, we would still recommend conversion to a combi. This is for two reasons – to save space and save energy. How does a combi boiler save energy? It does so by only heating the water on-demand or when needed. Whilst a system boiler stores water in an unvented cylinder and will have to reheat it multiple times to keep it hot.
Below are our recommendations for the best combi boilers for smaller properties:
|Viessmann||Vitodens 100-W Combi||26||£1,042.20 inc. VAT||Gas/LPG|
|Worcester Bosch||Greenstar 25i Combi||24||£911.98 inc VAT||Gas/LPG|
|Vaillant||ecoTEC pro Combi||24||£976.32 inc VAT||Gas/LPG|
|Grant UK||Vortex Eco External System 21-26||26||£2,465.31 inc VAT||Oil|
|Viessmann||Vitodens 050-W||29||£825.60 inc VAT||Gas/LPG|
Please note: The prices above are from an online plumbing wholesaler for the boiler only, and do not cover installation costs or other extras.
Aside from the Grant UK Vortex Eco External System 21-26, all of the other boilers we have recommended are mains gas boilers, these can be used with LPG with a conversion kit.
As combi boilers provide heating and hot water “on-demand” and don’t require additional water tanks, they are not suitable for larger properties with more bathrooms due to the chance that 2 or more people may require hot water at the same time.
Which boiler is best for a semi-detached, mid or end-terraced house with 3-4 bedrooms and 2 bathrooms?
A 3-4 bedroom house will usually have 1 bathroom, an en suite and maybe a toilet. With multiple locations requiring hot water, a higher capacity (28KW to 35KW) combi boiler will be able to fulfil the hot water demands of a property of this size. However, a new, energy-efficient conventional boiler (18kW to 24kW) with a water tank is also an option.
Alternatively, storage combi boilers such as the Viessmann 111-W Storage Combi Boiler with an in-built hot water storage tank will be able to provide the hot water which a property of this size requires. Depending on your mains water pressure, this boiler can give you up to 20 litres per minute easily.
Below are our recommendations for the best boilers for an average 3-4 bedroom house:
|Viessmann||Vitodens 111-W Storage Combi Boiler||26||£1,516 inc. VAT||Gas/LPG|
|Viessmann||Vitodens 100-W Combi Boiler||35||£1,200 inc. VAT||Gas/LPG|
|Worcester Bosch||Greenstar Highflow 440CDi Floor Standing Combi Boiler||29||£2,109 inc. VAT||Gas/LPG|
|Ariston||Clas ONE||30||£658 inc. VAT||Gas/LPG|
|Viessmann||Vitodens 200-W Combi with Weather Compensation (98% Efficiency)||30||£1,515 inc. VAT||Gas/LPG|
|Viessmann||Vitodens 050-W Combi Boiler||35||£870 inc. VAT||Gas/LPG|
|Grant||Vortex Eco External System 26-35||26||£2,169.17 inc VAT||Heating Oil|
Please note: The prices above are from an online plumbing wholesaler for boiler only, and do not cover the installation costs or any extras.
Again, all boiler models shown above can be used for Gas or LPG (with a conversion kit). The only two exceptions are the Grant which is an oil boiler, and the Viessmann Vitodens 200-W which doesn’t require an LPG conversion kit because it adapts to different fuel types automatically.
Obviously, as your house size goes up, so will your heating and hot water demands. This means a more powerful boiler is required to heat and provide hot water.
We do not recommend a small capacity combi boiler for a property this size. No heating expert would, this is because smaller capacity combi boilers won’t be able to cope with multiple showers, taps and appliances being used at the same time.
However, as we mentioned above, there are some high capacity storage combi boilers that may be suitable.
Our recommendations for the best boilers for a larger detached house or bungalow with more than 4 bedrooms and multiple bathrooms are:
|Viessmann||Vitodens 111-W Storage Combi Boiler||35||£1,743 inc. VAT||Gas/LPG|
|Viessmann||Vitodens 100-W Open Vent||35||£1,319 inc. VAT||Gas/LPG|
|Worcester Bosch||Greenstar FS 30CDi Regular||30||£1,532.27 inc. VAT||Gas/LPG|
|Vaillant||EcoTEC Plus 438 Open Vent||38||£1,582 inc. VAT||Gas/LPG|
|Grant||VortexBlue Internal Sealed System 26||36||£2,370 inc. VAT||Oil|
|Viessmann||Vitodens 222-F Floor Standing Storage Combi Boiler||35||£2,850 inc. VAT||Gas/LPG|
|Viessmann||Vitodens 242-F Floor Standing Storage Combi Boiler (Solar Integration)||26||£4,748 inc VAT||Gas/LPG|
Please note: The prices above are from an online plumbing wholesaler for boiler only, and do not cover the installation costs or any extras.
You may have noticed that we recommended two large Viessmann floor standing storage combi boiler models above. These are space-saving innovations from Viessmann, which mean you don’t require an additional unvented cylinder.
These Viessmann boilers also have what’s called CLS (Cylinder Loading System) technology. When we’re talking about which boiler is best, these boilers are definitely top of the pile.
Most unvented cylinders which work with a regular or system boiler use a heating coil to heat up the cylinder. The CLS technology replaces the coil with a plate heat exchanger. A DHW (domestic hot water) pump circulates the cold water from the bottom of the cylinder, through the plate heat exchanger and puts the hot water back to the top of the cylinder. This allows it to work much quicker than a conventional cylinder and means that a 100-litre cylinder with CLS provides the same performance as a 200-litre unvented external cylinder.
The below diagram explains things in more detail:
If you’re looking for the best boiler for a larger property without having to install an extra tank, we would thoroughly recommend the Viessmann Vitodens 222-F or the Vitodens 242-F.
Now that we’ve looked at which boiler is best for your property type, let’s take a look at the best boiler brands available in the UK:
Viessmann is a fourth-generation family German boiler manufacturer, which was established in 1917 and entered the UK market in 1989. In addition to the UK, they also operate in 30 other countries around the world.
Viessmann is renowned for its use of renewable energy and for its focus on maximum efficiency. They offer solutions for heating, cooling, power and air conditioning for domestic, commercial and industrial applications.
The Viessmann boiler range comprises futureproof gas condensing boilers, heat pumps, combined heat and power units, oil boilers, domestic hot water cylinders, steam boilers and commercial hot water boilers.
Viessmann’s entire UK boiler range is manufactured at their global headquarters in Allendorf, Germany.
In terms of domestic boilers, Viessmann’s UK market share continues to grow year-on-year, whilst they are also the frequent recipient of accolades including the Red Dot Award, HVR Awards and Which? Best Buy awards.
Key to Viessmann’s success is the use of their patented Inox-Radial stainless steel heat exchanger in every boiler in their range. This technology ensures efficiency, less impact on the environment and lower energy bills.
Founded in 1978, Grant is one of the UK’s leading manufacturers of domestic oil boilers
Grant is renowned for manufacturing straightforward products which feature sophisticated technology but are low maintenance and simple to install.
With environmental responsibility being key to its boiler range, Grant manufactures products that respond to the challenges of rising heat costs whilst protecting the environment by being efficient and making the best use of natural resources.
The Grant range comprises oil boilers, air source heat pumps, underfloor heating, radiators and biomass boilers.
Grant is also the only oil boiler manufacturer to achieve Which? Best Buy awards for three years running. In addition to this, they are also the frequent recipient of various highly coveted industry awards.
Originally founded in 1962 in the UK, Worcester became part of the Bosch Group in 1996. Today, they are the UK’s market leader in domestic boilers.
Based in Worcester, all Worcester Bosch gas boilers are manufactured at this site, whilst its oil boilers are manufactured at an additional site in Clay Cross, Derbyshire.
Worcester Bosch is renowned for its commitment to the environment and the innovation employed across its product range. This product range includes condensing boilers, smart thermostats, digital controls, solar solutions and air conditioning heat pumps.
The quality of Worcester Bosch’s product range has been recognised by being awarded a Which? Best Buy award for 11 years for its Greenstar gas boiler range, whilst they have a Royal Warrant for supplying boilers to Her Majesty The Queen’s Sandringham Estate.
Established in 1874, Vaillant is a completely family-owned German manufacturer of boilers based in Remscheid, North Rhine-Westphalia.
One of the leaders in the European heating industry, Vaillant is a pioneer in boiler technology and not only patented the “closed-system” gas-fired bathroom boiler in 1894 but also developed the first central heating boiler in 1924 and pioneered the combi boiler over 35 years ago.
Today, Vaillant is noted for its usage of renewable technologies and for developing systems that utilise sustainable energy sources. Due to this commitment to the environment across its entire product range, Vaillant products are noted for their high energy efficiency ratings and low emissions.
The Vaillant product range comprises gas boilers, air, ground and water source heat pumps, solar thermal hot water solutions, heating controls, thermostats and cylinders.
Vaillant’s quality has been recognised by being awarded Which? Best Buy awards, the Quiet Mark approval and the Superbrands title.
Ariston was founded in Marche, Italy in 1930 and has been manufacturing boilers since 1960.
Today, Ariston is number 4 in the world for boilers and number 1 in the world for hot water. Seen as a mid-range boiler brand, they are well-established throughout Europe and are an emerging brand in the UK.
Predominantly known for space-saving boilers, Ariston offers options for both commercial and domestic applications. The Ariston range comprises condensing boilers, gas-fired water heaters, electric water heaters and air source heat pump cylinders.
Whilst a mid-range boiler brand, Ariston is noted for value for money, product efficiency, simplified installation and its use of futureproof technology.
How we chose the above brands…
The above boiler brands were selected based on the quality of their components, the availability of parts and the level of service which they provide to customers. Each of these brands are not just trusted names within the UK and Europe but all around the world. However, as with everything we believe that you should make an educated, informed decision in choosing the best brand and product for your specific needs.
Above all, we recommend the Viessmann brand and for this reason, we are Viessmann Trained Installers. There are many reasons why we choose to work with Viessmann, these include the following:
Manufactured in-house, Viessmann’s patented Inox-Radial stainless steel heat exchanger is what sets Viessmann apart from other boiler manufacturers in the UK.
Specifically developed for efficiency, the Inox-Radial heat exchanger is stainless steel and manufactured with chromium content. This makes it highly resistant to corrosion in a wide range of pH levels. Many other boiler manufacturers utilise aluminium heat exchangers which are more prone to corrosion, which will ultimately affect efficiency.
Viessmann has a long history of providing heating solutions for commercial applications. Viessmann’s commercial product range includes commercial boilers and industrial heating systems. Whether for a single commercial unit, a large factory or a local heating network, Viessmann has a solution.
Notable large-scale commercial applications of Viessmann heating solutions include the grandstand at Cheltenham Racecourse, Blue Planet Aquarium in Cheshire Oaks, Lotte World Tower in Seoul – which is the world’s second-tallest building, the Dacia vehicle manufacturing plant in Romania, the Turkmen capital building, and Table Rock Welcome Centre in Niagara Falls.
As Viessmann is able to offer its services at such a high level, this provides us with confidence in the brand at a consumer level.
We believe that Viessmann has the most impressive boiler range in the world – this is because they have a solution for every heating need, offer multiple choices of fuel including gas, LPG, oil and solar, and offer excellent levels of efficiency, with 98% efficiency being offered on the majority of their domestic boilers.
In addition to this, the Viessmann range comprises floor standing and space-saving boiler options.
Viessmann’s focus remains on making the highest efficiency, technologically brilliant boilers. It is this focus which has seen the Vitodens range awarded Which? Best Buy status every year since 2017.
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