Is the world of boiler comparison too noisy? This guide will reveal some of the best boiler manufacturers you could buy — learn more about the best brands and see a side-by-side price comparison below.

As you’re probably aware, installing a new boiler is not cheap, unless you get some help from your boiler cover provider. A typical combi could cost £2,000-£3,000 including labour. Oil boilers, while more seldom used, tend to be much more expensive.

Data on the radiator & boiler market share in the UK exists but is restricted. Figures are complicated, too, because the UK has an open market where boilers, for example, can be imported and sold without the need to publish information publicly.

We’re using recent data from consumer group Which’s ‘Best Buy’.

Worcester Bosch (the undefeated?)


Having over eight years (2010-2018) as Which’s ‘Best Buy’, the Worcester Bosch boiler is among the UK’s current market leaders. In 2017, they sold 490,000 boilers in the UK.

For an average semi-detached home with 2 bedrooms and 2 bathrooms, the Greenstar 12ri and 15ri models are recommended by the Worcester Bosch website.

If you live somewhere smaller, this website may recommend something different, more suited to your home.

They’re certainly the most well-known. While Worcester Bosch is considered by many to be the best boiler brand available, we’re going to challenge that a bit down below.

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They offer boilers in all shapes and sizes:

  • Oil
  • Combi
  • System
  • Regular

They’ve had huge success in sales with models like the CDI and a Greenstar 25I/30I. The warranty ranges from 5-10 years. The exact warranty depends on the boiler you choose, and the other Worcester branded products you use. For example, adding a Worcester Bosch system filter will add on a further year’s warranty.

Who are some of the best boiler providers

Worcester Bosch boiler prices were among the most expensive, comparable to Baxi and Vaillant. The Worcester Bosch Greenstar I starts from £1,770.

80% of people on Trustpilot rated them ‘Excellent’

Worcester Bosch Greenstar 12Ri

  • Worcester Bosch’s ‘Greenstar’ is officially in its best-selling range
  • This is a regular boiler that fits within a standard kitchen cupboard
  • Suitable for small to medium homes
  • Perfect for homes that require a hot water storage cylinder
  • Energy Efficiency: A-rated
  • 10-year warranty

Other key features:

  • Central heating output (kW): 12
  • Dimensions (mm) height x width x depth: 600 x 390 x 270 (this boiler fits inside most cupboards).
  • Hot water flow rate 35°c (litres per minute) – Hot water flow rate 40°c (litres per minute). The flow rate represents the number of litres of hot water that come out of the tap in a minute.

Worcester Bosch Greenstar 15Ri

  • Best-selling range
  • Suitable for small to medium homes
  • Suitable for older properties, or those wishing future proof the home with extra power
  • 10-year warranty

Other key features:

  • Central heating output (kW): 15
  • Dimensions (mm) height x width x depth: 600 x 390 x 270 (this boiler fits inside most cupboards).
  • Hot water flow rate 35°c (litres per minute) – Hot water flow rate 40°c (litres per minute). The flow rate represents the number of litres of hot water that come out of the tap in a minute.

In an ‘Ideal’ world

Another close competitor is Ideal who sold 415,000 boilers in 2017.

They’re a British manufacturer that has grown exceptionally over the last decade.

Thankfully, unlike Worcester, their warranty is more straightforward.

Ideal offer warranties that are:

    • 2 Years – Ideal Logic
    • 7 Years – Ideal Logic Plus
  • 10 Years – Ideal Vogue (when fitted with an Ideal system filter)

Ideal Boilers are more of an anomaly when it comes to price. They are fast approaching the reputation of a premium brand, but they sit more or less in the median on the price

The boilers that rival Worcester Bosch, tend to be 10-15% cheaper when using a local installer. Of course, with Heatable being so good value when it comes to Worcester boilers, they tend to work out at around the same price.

78% of people on Trustpilot rated them ‘Excellent’


Another manufacturer sold 300,000. Price-wise, expect them to be just slightly less than a Worcester Bosch equivalent. Reviews are largely positive, with 79% rating them ‘Excellent’ on Trustpilot.

Best Boiler Choice


A market leader at the turn of this century only sold 40,000 in 2017. Their EcoTec range is by far the best-selling boilers. Reviews look positive,  with 77% rating them ‘Excellent’ on Trustpilot.

Their lacklustre sales maybe because they do not have the slick marketing that Worcester does, but the customer support is guaranteed.

Generally, their products have a 2, 3- or 5-year warranty attached to them.

Expect the price of Vaillant boilers to be in a similar price band to Worcester Bosch, Ideal Boilers and Baxi’s equivalent products.


Are behind them all in the UK with just 35,000 (2017).

They’re a German manufacturer of heating, industrial, and refrigeration systems headquartered in Allendorf, Germany – and a company of dark stallions if they’re reputation is anything to go by.

While it has not won a large following in the UK just yet, this is due in part to its higher price-point for some of its products, and perhaps to the ongoing uncertainties with importing EU goods into Britain.

Having taken home a Which? Best Buy award, the Viessmann Vitodens 100-W (and its sibling Vitodens 050-W) definitely do offer value for money against their rivals – depending on the kind of boiler you go for – especially when considering their patented internal components will probably make a more durable boiler.

Below is how Viessmann measure up for price against Which? Best Buy regulars:

Worcester Bosch£2,189+ 5%
Vaillant£2,024+ 2%
Viessmann£1,990– 4%
  1. The Viessmann Vitodens 200-W is one of the top-performance combi boilers in 2020. It’s made number 1 in many central heating reviews around Europe and the rest of the world. The 200-w is one of the best domestic boilers available on the market:

Viessmann Vitodens 200-W Key Features:

  • 98% energy efficiency – meaning almost none of the fuel is wasted in its conversion into heat.
  • 5-inch colour touchscreen. Easy to operate the Vitotronic control unit.
  • Can be controlled via a smartphone app and internet (with optional Vito-connect 100 WLAN adaptor)
  • Smart thermostat compatible
  • Environmentally responsible matrix cylinder burner
  • High-quality Inox-radial stainless-steel heat exchanger
  • Lambda pro-control plus combustion controller ensures consistently high energy efficiency
  • Help keep the maintenance costs down to reduce environmental impact
  • Automatic adjustment to different gas types (Natural Gas, LPG, Biogas)
  • Quiet: only 34 decibels
  • Compact dimensions, only 450 mm wide
  • Pressure release valve and condensate combined (Easy Installation)
  • Energy efficiency class: A
  • Optional remote fault notifications for Viessmann Trained Installers

An alternative is the Viessmann Vitodens 100-w, another example that stands among the best combi boilers currently available in 2020. As a premium boiler, it’s positioned well bridge between affordable combi boilers and the absolute, top-of-the-range premium. This model is £500 cheaper than the Vitodens 200-w. It has an energy efficiency of around 94% with programmable, smart controls and weather compensation.

This is easily an ideal combi boiler for a 5+ bedroom home. Again, prices depend on the central heating output. The 100-W comes in three different variations. Recommend retail prices are made on 2018 estimates and will vary:

Vitodens 100-W 26kW         £2,247

Vitodens 100-W 30kW         £2,295

Vitodens 100-W 35kW         £2,530

Viessmann Vitodens 100-W Key Features:

Which? Best Buy Gas Boilers (September 2019)

  • High-quality stainless steel Inox-adial heat exchanger
  • Environmentally responsible matriX cylinder burner
  • Backlit LCD touch screen for easy operation
  • Class A-rated for energy efficiency
  • Pressure release valve and condensate combined for easy installation
  • Compact design and low weight
  • Quiet operation with low fan speed
  • Available in outputs from 4.7 to 35 kW
  • Low CO2 emissions for reduced environmental impact
  • Optional room thermostats available
  • Up to 10 years of extended warranty available
  • LPG conversion kit available
  • An even cheaper alternative, Viessmann Vitodens 050-W is one of the more affordable combi boilers you can buy in the UK.  Its relatively small price tag (around £750) makes it a serious rival to the Greenstar 12ri. Its good value does not mean this boiler cannot do everything the more expensive boilers in the Viessmann family can do.

Again, Viessmann offers their patented Inox-Radial Stainless Steel Heat Exchangers, a robust and highly efficient heat exchanger.

Viessmann Vitodens 050-W Key Features:

     Which? Best Buy for Gas Boilers (September 2017)

  • Ultra-compact – Just 707mm in height
  • DHW output ratings of 5.9 to 35 kW
  • High-quality stainless steel Inox-Radial heat exchanger
  • Stainless steel cylinder burner
  • Integral instantaneous water heater
  • Low CO2 emissions for reduced environmental impact
  • Digital user interface with lcd display for easy operation
  • Optional room thermostats, plug-in time clock and wireless receiver
  • Up to 10-year extended warranty available
  • Class A-rated for energy efficiency

Viessmann hasn’t yet ‘claimed’ their profile on Trustpilot and they’ve only got one average review there – but this is definitely a fluke, and this most certainly company to watch.

Why is this important?

Assessing a company’s health and market share is not trivial. Customers like to know this information, as it means that deciding a boiler to use for the next decade and wanting to know that after-sales care will still exist throughout that time duration is critical.

In summary, while the Worcester Bosch range has some strong boilers, Viessman is just as reliably worthy of their ‘Which? Best Buy’ awards too with friendly user controls and thoughtful German engineering. The Viessmann Vitodens range is some of the best boilers the UK do not seem to be buying. The reasons for this may be numerous, and the work for more exploratory marketing and advertising work on their team’s part.

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