Article

Best Combi Boilers in the UK (and Which to Avoid)

Best Combi Boiler

The Worcester 4000 is the best all round combi boiler money can buy currently. It’s an affordable, quiet and very capable boiler for small to medium sized homes.

Read on for more about the Worcester 4000 and other models featured in our top 10 combi boilers list.

So, you need a new boiler but not sure where to start. You know it’s a combi, and for many reasons, that’s the best choice. Combi boilers are efficient, space-saving, cheaper to install, and provide heating and hot water on demand.

Combi boilers don’t need large expensive hot water tanks, and are the most widely installed and supported boiler in the UK. But which brand and model of combi is best?

With feedback from Gas Safe registered heating engineers we explore the options and provide you with the answers to ensure you get the best, most reliable and energy-efficient combi boiler for your UK home’s central heating installation.

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We’ve looked at many areas to produce this top 10 with a particular focus on the following.

Top boiler brands: We include boilers from brands Worcester, Viessmann, Ideal, Vaillant, Baxi & Alpha, which are all known for producing reliable boilers at different price points.

Price: Here at WhatPrice we specialise in ensuring homeowners get the best deal. That’s why we’ve scoured the internet and listed below how much you can expect to pay for a new gas boiler, based on a like-for-like replacement.

Long warranties: Every boiler we include must come with at least 7 years warranty, many have much longer but always check that your installer can supply the boiler with the maximum warranty available, they may have to fit the brands filter or be an accredited installer.

High efficiency: We all want the most efficient combi boiler, right? It saves money and helps the planet. That’s why all the boilers in our top 10 are A-rated to ensure you reap the benefits.

Customer support: We’ve spoken to engineers who can all vouch for the boiler brands we recommend, plus we’ve checked all the boilers here are backed by a UK nationwide support network.

But without further ado let’s take a look at the best combi boilers in the UK, these are not ranked in any particular order as every boiler has a slightly different application, we can thoroughly recommend every one of them.

Top 10 Best Combi Boilers

Make & ModelBest Combi Boiler forWarranty*Target Price
Worcester Bosch Greenstar 2000Best for those who value a quiet combi boiler7 yrs£2,200
Worcester Bosch Greenstar 4000Best for all round affordability & reliability12 yrs£2,400
Viessmann Vitodens 050-WBest for small homes, flats & tight spaces10 yrs£2,600
Viessmann Vitodens 100-WBest for longevity with its stainless steel heat exchanger10 yrs£2,800
Vaillant EcoTec ProBest for after sales service and support7 yrs£2,700
Vaillant EcoTec PlusBest combi for larger homes with high hot water demands10 yrs£2,900
Ideal Vogue MaxBest combi boiler for larger homes on a budget12 yrs£2,100
Ideal Logic+Best for tight fit cupboard spaces7 yrs£2,450
Baxi 800 Combi 2 BoilerBest for engineer feedback as a great boiler10 yrs£2,600
Alpha E-Tec NX Combi BoilerBest for being the cheapest combi with long warranty11 yrs£1,900
*This is the maximum warranty available. E.g. to qualify a Worcester 4000 for 12 years the installer must be Worcester Bosch accredited.

Best Worcester Combi Boilers

About Worcester Bosch

Worcester Bosch, the stalwart of the boiler world, has led the pack for many years in producing the best combi boilers in the UK. Known for their reliability and great customer service, Worcester Bosch are still based in the town they share the name of, manufacturing boilers in both Worcester and Clay Cross, Derbyshire. Widely recommended by gas engineers and homeowners alike, you won’t go far wrong choosing a combi from this award-winning brand.

Pros
  • Proven reliability
  • Up to 12 year warranty
  • Widely supported
  • Good customer support
  • Boilers made in Britain
Cons
  • More expensive initially
  • Parts prices can be on the higher side

Worcester Bosch Greenstar 2000 Combi Boiler

Worcester Bosch Greenstar 2000 Combi Boiler

A lower cost option that’s suitable for smaller homes and flats. It’s compact enough to fit inside a kitchen cupboard and Quiet Mark certified so won’t wake you in the middle of the night.

Available in two outputs of 25 & 30kW, the lower output of the two will be suitable for flats and smaller sized homes with one bathroom, anything larger then opt for the 30kw model.

This is a popular and reliable model from a big brand at a lower cost, if your budget allows however go for the Worcester 4000 which is slightly more efficient and comes with a longer warranty.

Worcester 2000 Features
TypeCombi Natural Gas & LPG
Heat output 25kW & 30kW
Efficiency rating94% A-rated
Noise level47db (Quiet Mark certified)
Warranty7 years
Hot water flow rate 35°c10 l/min (25kW), 12 l/min (30kW)
Dimensions724 x 400 x 300
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,200
Typical applicationSmall houses & flats

Worcester Bosch Greenstar 4000 Combi Boiler

Worcester Bosch Greenstar 400 Kitchen HERO CROPPED

The Greenstar 4000 is the most popular combi boiler from Worcester for good reason, it’s efficient, compact, quiet and packaged in a modern sound insulated case that looks pretty good on your wall.

Only slightly more expensive than it’s smaller sibling, the Worcester Greenstar 2000, its additional hot water output makes it a worthwhile upgrade if you’re considering the Worcester 2000 vs Worcester 4000.

The boiler is also popular with Installers, it’s easy to fit and to maintain with front access to all components. It’s a good choice for anyone looking for a reliable combi for a small to medium sized home.

Worcester 4000 Features
TypeCombi Natural Gas & LPG
Heat output 25kW & 30kW
Efficiency rating94% A-rated
Noise level45db (Quiet Mark certified)
Hot water flow rate 35°c10.2 l/min (25kW), 12.3 l/min (30kW)
WarrantyUp to 12 years
Dimensions724 x 400 x 310
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,400
Typical applicationSmall to medium sized houses & flats
1 bathroom

Best Viessmann Combi Boilers

About Viessmann boilers

A leading German brand, Viessmann is known for its high quality engineering making efficient and reliable boilers for decades. Upfront installation prices are generally higher than other combi boilers in the market due to features such as a stainless steel heat exchanger as opposed to aluminium in most others, this will increase the lifespan of the boiler but does mean a higher initial cost, it will however make it one of the best combi boilers for longevity.

Whilst not as widely installed as Worcester Bosch combis, engineer feedback is good for Viessmann, they are easy to install and maintain. Some installers have suggested that parts may be not be as widely available as other brands, which may be a consideration. Their Trustpilot rating is still good at 4.4/5, but looking at the number of 1 star reviews suggests there are issues with customer support and warranty claims.

Pros
  • German engineered reliability
  • Stainless Steel heat exchangers
  • Compact boilers
  • Good efficiency
Cons
  • Reviews suggest customer support could be better
  • Mixed experiences with warranty claims
  • Not as widely supported as Worcester

Viessmann Vitodens 050-W Combi Boiler

Viessmann Vitodens 050

The Vitodens 050-W is known for its high efficiency, compact design, and quiet operation. It comes with smart technology features, including Wi-Fi connectivity for remote control via a smartphone and remote support.

Supplied in 25kW & 30kW models the Vitodens 050 combi boasts 7 years warranty and includes a stainless steel heat exchanger as standard. Being hydrogen ready you’ll be future proofed for changes in your gas mixture should this happen in your area.

A very compact and quiet boiler with a very user friendly control panel, it’s perfect for small houses and flats as it can fit inside a kitchen cupboard.

Viessmann Vitodens 050-W Features
TypeCombi Natural Gas & LPG
Heat output 25kW & 30kW
Efficiency rating92% A-rated
Noise level47db (25kW), 49db (30kW)
Hot water flow rate 35°c10.2 l/min (25kW), 12.2 l/min (30kW)
WarrantyUp to 10 years
Dimensions700 x 400 x 300
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,600
Typical applicationSmall to medium sized houses & flats
1 bathroom

Viessmann Vitodens 100-W Combi Boiler

Viessmann Vitodens 100

The Vitodens 100-W is one of the most popular models due to its exceptional build quality and efficiency. It’s cost being slightly higher than most is justified with the use of high quality components such as a stainless steel heat exchanger, which enhances durability and efficiency.

It’s smart WiFi integration enables remote support by the manufacturer ensuring minimum downtime in the event of a breakdown.

Available in 3 outputs the Vitodens 100-W combi boiler is best for small to medium sized homes with 1 or more bathrooms.

Viessmann Vitodens 100-W Features
TypeCombi Natural Gas & LPG
Heat output 26kW, 30kW & 35kW
Efficiency rating94% A-rated
Noise level49db (26kW), 50db (30kW), 50bd (35kW)
Hot water flow rate 35°c10 l/min (25kW), 12 l/min (30kW), 14 l/min (35kW)
WarrantyUp to 12 years
Dimensions700 x 400 x 360
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,800
Typical applicationMedium sized houses & flats
1 or more bathrooms

Best Vaillant Combi Boilers

About Vaillant

Vaillant is a prestigious German boiler brand that focuses on quality, efficiency, and innovation. With a higher price point than Worcester places it firmly in the premium category and is best known for its award-winning EcoTEC combi boilers, which we look into in more depth below.

Vaillant is the second largest boiler manufacturer in Europe and is always a clear favourite amongst installers for their build quality, ease of maintenance and parts availability. Vaillant is unbeatable in this regard.

Pros
  • High efficiency
  • Excellent build quality
  • Very well regarded by installers
  • Great customer support
  • Quiet operation
  • Made in Britain
Cons
  • On the pricier side
  • Repairs can be expensive

Vaillant EcoTec Pro Combi Boiler

Vaillant EcoTec Pro Combi Boiler

Vaillant’s EcoTec Pro boilers offer reliable performance with a focus on energy efficiency and lower emissions. Manufactured in Vaillant’s Derbyshire plant it’s another boiler, similar to Viessmann, that contains a Stainless Steel heat exchanger, this ensures longevity and superior heat transfer.

Not only is this boiler future proofed being hydrogen ready it’s also compatible with Vaillant’s aroTHERM plus air source heat pump, making it the perfect entry into renewable systems.

Available in 3 output options this Vaillant combi is a great option for small to medium-sized homes.

Vaillant EcoTec Pro Features
TypeCombi Natural Gas & LPG
Heat output 24kW, 28kW & 30kW
Efficiency rating93% A-rated
Noise level49db
WarrantyUp to 7 years
Hot water flow rate 35°c9.6 l/min (24kW), 11.1 l/min (28kW), 12.3 l/min (30kW)
Dimensions720 x 440 x 338
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,700
Typical applicationSmall to medium sized houses & flats
1 bathroom

Vaillant EcoTec Plus Combi Boiler

Vaillant EcoTec Plus Combi

The EcoTEC Plus is one of Vaillant’s premium combis, offering higher efficiency, smart connectivity, and excellent British build quality.

It’s a powerhouse of heat available in 4 outputs up to 40 kW making it our best combi for larger homes with high hot water demands.

Like its smaller sibling it’s fitted with a stainless steel heat exchanger and smart controls. It’s a favourite of heating engineers nationwide and for good reason. It carries a higher cost than most combis but you won’t go wrong choosing this boiler.

Vaillant EcoTec Plus Features
TypeCombi Natural Gas & LPG (not 40kW)
Heat output 26kW, 32kW, 36kW & 40kW
Efficiency rating94% A-rated
Noise level46db (26kW), 45db (32kW), 47db (36kW), 49db (40kW)
Hot water flow rate 35°c10.6 l/min (26kW), 13 l/min (32kW), 14.6 l/min (36kW), 16.3 l/min (40kW)
WarrantyUp to 10 years
Dimensions720 x 440 x 352, 720 x 440 x 386 (40kW)
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,900
Typical applicationMedium to large sized houses & flats
1+ bathrooms

Best Ideal Combi Boilers

About Ideal Boilers

Ideal Heating are a popular mid-range brand from Hull, Ideal have specialised in reliable and affordable boilers with solid after-sales support since 1906 and are another manufacturer making boilers in Britain.

Whilst some older Ideal models such as the Ideal Icos & Izar were notorious for high failure rates the company has addressed those issues in recent years and are now known for excellent reliability and customer support, they also have a good reputation for responding well to warranty claims.

Pros
  • Affordable
  • Reliable
  • Easy to maintain
  • Great customer support
  • Good warranty record
  • Made in Britain
Cons
  • Basic features

Ideal Vogue Max Combi Boiler

Ideal Vogue MAX Combi

The Ideal Vogue Max is available in 3 versions up to 40kW in output, making it the best choice for larger homes. It’s simple to fit and use with rotary dials and an LCD display.

With up to a 12-year warranty, this Vogue Max is a reliable unit backed by a company with a good track record in customer support. It also comes with an Ideal filter in the box and stainless steel heat exchanger as standard.

The Vogue Max combi boiler is a solid choice and won’t break the bank.

Ideal Vogue Max Features
TypeCombi Natural Gas & LPG
Heat output 26kW, 32kW & 40kW
Efficiency rating93% A-rated
Noise level47db (26kW), 50db (32kW), 49db (40kW),
Warranty12 years
Hot water flow rate 35°c10.6 l/min (26kW), 13.1 l/min (32kW), 16.4 l/min (40kW)
Dimensions740 x 450 x 330
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,100
Typical applicationMedium to large sized houses & flats
1+ bathroom

Ideal Logic+ Combi Boiler

Ideal Logic Combi

The smallest combi in our list, the Ideal Logic+ is the best combi for kitchen cupboards and tight spaces. It’s also incredibly efficient and quiet, what’s not to like?

With an easy to use colour screen and simple interface the Logic plus is designed and made in the UK, specifically for UK homes. Whilst being very compact the boiler can also be fully serviced from the front, so you won’t need your kitchen dismantling should something go wrong.

Ideal Logic+ Features
TypeCombi Natural Gas & LPG
Heat output 24kW, 30kW & 35kW
Efficiency rating94% A-rated
Noise level50db (24kW), 46db (30kW), 46db (35kW),
Hot water flow rate 35°c9.9 l/min (24kW), 12.4 l/min (30kW), 14.5 l/min (35kW)
Warranty7 years
Dimensions700 x 395 x 278
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,450
Typical applicationSmall to medium sized houses & flats
1 bathroom

Best Baxi Combi Boiler

About Baxi Boilers

Baxi Heating is part of a larger group consisting of well known brands including Megaflo, Heatrae Sadia and Main Heating. Manufacturing boilers, air source heat pumps and hot water tanks within the UK, the company has built a reputation of producing solid, reliable boilers. In fact Baxi produced the Baxi Bermuda back boiler which was ubiquitous in sixties homes at the time.

Very well regarded by heating engineers and few complaints from homeowners makes choosing a Baxi combi boiler an easy choice.

Pros
  • Highly regarded by heating engineers
  • Simple and reliable
  • Easy to maintain
  • Great customer support
  • Made in Britain
Cons
  • Not as feature rich as others

Baxi 800 Combi 2 Boiler

Baxi 800 Combi 2 boiler

Available in 3 models (824 Combi 2, 830 Combi 2 & 836 Combi 2) the 800 series is a lightweight and compact boiler suitable for installation within kitchen cupboards.

The Baxi 800 contains a built in filling loop, brass fluid fittings (most others are plastic) and a stainless steel heat exchanger which ensures rock solid reliability. On the outside you get no-frills analogue pressure gauge, rotary dials and an LCD display for ease of use. Inside the box you’ll get an Adey Micro2 magnetic system filter which is an outstanding filter.

Engineer feedback for this boiler is very positive, they say it’s easy to fit, service and quiet in operation. Its compact size is a real bonus for houses with little wall space for a boiler.

Baxi 800 Features
TypeCombi Natural Gas & LPG
Heat output 24kW, 30kW & 36kW
Efficiency rating94% A-rated
Noise level50db (24kW), 51db (30kW), 51db (36kW),
Warranty10 years
Hot water flow rate 35°c10.2 l/min (24kW), 12.2 l/min (30kW), 15 l/min (36kW)
Dimensions700 x 395 x 285
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£2,600
Typical applicationSmall to large sized houses & flats
1+ bathroom

Best Alpha Combi Boiler

About Alpha Heating

Known for affordability and decent performance, Alpha manufacture gas boilers and air source heat pumps. They are one of the lowest cost boilers on the market but still include premium features such as a stainless steel heat exchanger.

A particular favourite of landlords due to the low cost and simple no-frills performance the Alpha E-Tec combi below is a popular model that ticks many boxes.

Pros
  • Budget friendly price point
  • Good warranties
  • Well regarded
Cons
  • Not the quietest
  • Basic features

Alpha E-Tec NX Combi Boiler

Alpha E-Tec NX 28kW Combi Boiler

The Alpha NX combi is the best value option we’ve found, providing high efficiency and reliability at a lower price point. It comes with a 7-year warranty as standard but shopping around we found it available with a whopping 11-year warranty.

It comes with a stainless steel heat exchanger and is available in two models of 28 & 33kW outputs making it the best combi boiler for small and medium sized homes.

You may wonder what the support would be like for such a cheap combi, but looking on Trustpilot you’ll see Alpha Heating perform very well with a score of 4.6/5 from over 6,400 reviews.

This is a simple, straightforward and efficient boiler at a great price, you can’t go wrong.

Alpha E-Tec NX Features
TypeCombi Natural Gas & LPG
Heat output 28kW & 33kW
Efficiency rating94% A-rated
Noise level52db (28kW), 54db (33kW)
WarrantyUp to 11 years
Hot water flow rate 35°c12.1 l/min (28kW), 14.1 l/min (33kW)
Dimensions712 x 440 x 255
Hydrogen readyYes
Boiler controlsWireless
Typical installation price£1,900
Typical applicationSmall to medium sized houses & flats
1+ bathroom

Boiler brands to avoid

All of the brands featured in our Top 10 best combi boilers above are known for reliability and customer service, on the flip side there are a couple of brands which keep coming up as having reliability issues which are Ferroli and Biasi, both fared very poorly in a Which? survey of boiler brands. For the sake of a few extra pounds it’s worth investing in a gas boiler that’ll provide years of trouble free service, the last thing you need on a cold winter’s morning is a broken boiler.

Combi boiler FAQs

The UK government has announced plans to ban the installation of new gas boilers in newly built homes from 2025 and in all homes from 2035 as part of its drive to reach net zero. Existing gas boilers won’t be banned, but you may need to consider alternatives in the future, such as heat pumps or hydrogen-ready boilers. However, there’s nothing to worry about installing a new boiler in an existing home.

A combi boiler that is kept maintained can last between 10 to 15 years. Regular servicing, using original components, and addressing repairs as soon as they start can help extend the life of your boiler.

Worcester, Vaillant and Ideal are our favourites for building and supporting reliable boilers all within the UK.

It’s not quite as simple as saying one specific boiler is best, as every application is unique to each home’s central heating system and size. However, for a typical 3 bedroom 1 bathroom house in the UK you won’t go far wrong with a Worcester Greenstar 2000.

A like-for-like combi boiler replacement will cost on average £2,829. This is based on actual costs submitted to us by homeowners following a boiler installation.

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