Most Reliable Boilers in 2024

Last updated: May 3, 2024

Are you looking for the most reliable boilers in 2024 that guarantee optimal performance and peace of mind? Here we reveal the expert verdict.

New boilers rank as one of the most expensive purchases households make. According to the Energy Savings Trust, replacing a boiler can cost around £3,700 to £5,500, so it’s vital to ensure you get one you can rely on.

Choosing a reliable boiler ensures it will meet your heating and hot water needs without failure for years while maintaining high efficiency and overall performance.

But how exactly do you determine the most reliable boilers in 2024?

Reliability: the quality of being trustworthy or of performing consistently well.

Choosing the most reliable boilers with countless brands and models available can feel overwhelming.

This guide explores the most reliable boilers in the UK in 2024 to help you choose a quality product that won’t let you down.

Key Takeaways: Which Are The Most Reliable Boilers to Buy in 2024?

  • Worcester Bosch Greenstar 4000 – Best Overall Reliable Combi Boiler
  • Viessman Vitodens 100-W – Most Powerful Reliable Combi Boiler
  • Alpha NX Combi Boiler – The Most Reliable Affordable Boiler
  • Worcester Bosch Greenstar 2000 – Best Reliable Boiler for Small Homes
  • Valliant EcoTec Pro – Best Reliable Boiler for Large Homes

Most Reliable Boilers UK – What We Considered:

We considered the following factors to determine the most reliable boilers in the UK in 2024:

  • Length of the boiler warranty offered by the brand. It shows trust in the durability of the product.
  • Any awards the brand has acquired.
  • Reputation based on reviews from customers and industry experts.
  • Technology and quality of the boiler components used, e.g., plastic vs metal.
  • Availability of spare parts.
  • Efficiency ratings.
  • The price point of their boiler models.
  • The manufacturer’s track record of innovation and consistent quality. These provide valuable insights into their commitment to producing dependable boilers. 
  • Aftercare quality – Are their customer services high quality?
  • Which? survey results from 10,018 homeowners and 198 heating experts and Gas Safe Engineers.
Best boilers

Worcester Bosch Greenstar 4000 (Best Overall Reliable Combi Boiler)

One of the most reliable boilers in the UK
Image by Worcester Bosch
  • Efficiency: 94% ErP rating
  • Output Range: 25kW to 30kW
  • Dimensions: 710 (h) x 400 (d) x 310 (w)
  • Warranty: 10 years

The Worcester Bosch Greenstar 4000 offers incredible reliability and value for money.

It’s A-rated and has an incredible efficiency of 94%, making it an excellent mid-range model with the most essential features and recent innovations at a competitive price point.

The Greenstar 4000 comes in a more compact design than the Greenstar i for a streamlined installation into your standard kitchen cupboard. 

It features excellent performance and you can choose between 25kW and 30kW power outputs or sizes.

The 25kW size is suitable for small properties and flats and has a flow rate of 10.5 l/min. The 30kW size is suitable for medium-sized properties with higher demand and has a flow rate of 12.3 l/min.

The Greenstar 4000 has a user-friendly LCD display and easy-to-use push control buttons. Thanks to wireless connectivity, you can connect the boiler to Bosch EasyControl and control the boiler remotely from your smartphone or other device.

It comes with a 10-year warranty for parts and labour and an intelligent filling system that ensures your boiler’s pressure is at its optimum level.

Why do we think Viessmann offers the best combi boilers? 

  • Which? Best Buy Award winner – titled as the UK’s “most reliable boiler”.
  • 10-year boiler warranty.
  • State-of-the-art German engineering – no plastic or rubber components (like some competitors).
  • Patented Inox Radial Stainless Steel Heat exchanger (not aluminium found in other boiler brands).
  • The only boiler with Lamda combustion control – maximising efficiency.  
  • Hydrogen ready – for the next generation of fuel.
  • The availability of parts is superb.
  • Excellent customer reviews and aftercare.

Check out our guide on boiler brands to avoid

Viessman Vitodens 100-W (Most Powerful Reliable Combi Boiler)

Vitodens is one of the most reliable boilers
  • Efficiency: 94%
  • Output Range: 19kW–32kW
  • Dimensions: 700(h) x 350(d) x 400(w)
  • Warranty: Up to 12 years

The best combi boiler for homeowners looking to secure a reliable and award-winning combi boiler is the Viessmann Vitodens 100-W boiler.

The Vitodens 100-W is a top choice if you’re looking for exceptional efficiency, a long lifespan, and quiet operations.

It features an impressive efficiency rating of 94% and the standout Lambda Pro technology that helps maintain maximum efficiency and burn rate.

Operating at only 35dB, the Vitodens 100-W is whisper-quiet and can ensure a peaceful home environment. It has an updated LCD touchscreen display and wifi integration so you can control and diagnose your boiler and even get remote assistance.

Phil Cox, head of Sales at Heatable and former Director of Sales at British Gas notes that what sets the Vitiodens 100-W apart is its “impressive connectivity, allowing for remote access to the boiler, performance monitoring, and the ability to diagnose potential faults.”

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Advanced technologies like the Inox-Radial heat exchanger and the modulating MatriX-Plus cylinder burner contribute to the Vitodens 100-W’s exceptional performance and efficiency.

Despite its compact size and lightweight design, the Vitiodens 100-W is also very powerful, making it an excellent choice for medium to large houses.

Why else do we think Viessman Combi boilers are a superb option? 

  • Awarded Which? Best Buy since 2018 onwards
  • Low CO2 emissions to help ease your carbon footprint and conscience.
  • Outstanding value thanks to superior internal components that ensure a longer-lasting boiler.

Alpha E-Tec NX Combi Boiler (Most Reliable Affordable Boiler)

  • Efficiency: 93% ErP rating
  • Output Range: 28kW–38kW
  • Dimensions: 712(h) x 440(d) x 255(w)
  • Warranty: 10 years

If you are looking for a combi boiler that offers maximum value for money, then the Alpha E Tec NX combi boiler is a superb option.

It’s accredited as A-rated with a 93% efficiency and comes in sizes or power outputs of 28kW and 38kW. The 28kW size has a flow rate of 12.1 l/min while the 38kW size has a flow rate of 15.9 l/min.

The Alpha E-Tec NX comes with a stainless steel heat exchanger, which is unheard of amongst budget boiler brands. Stainless steel is stronger than aluminium and can withstand extreme heat.

You don’t have to worry about longevity or corrosion with the Alpha E Tec, making it one of the most reliable combi boilers in the lower price range.

The expansion vessel of the Alpha E-Tec NX, which helps control pressure, is zinc-plated, allowing it to withstand corrosion and last much longer than standard models. 

The Alpha E-Tec has a Good Homes Magazine Award and countless 5-star reviews on Trustpilot.

It’s compatible with all the popular smart thermostats, including Tado, Hive, and Google Nest. You can integrate the boiler into the rest of your smart home hub, and take greater control of your heating.

Why else do we think Alpha Combi boilers are a superb option? 

  • Good Homes Magazine Approved (2024).
  • Competitive price point.
  • Superior parts and design at an affordable price.

Wondering how much a new boiler costs? Check out our guide on options available if you need a new boiler but can’t afford it, as well as boilers on finance and government boiler grants here.

Check out our video on how to vet boiler brands/models in the UK:

Worcester Bosch Greenstar 2000 (Best Reliable Boiler for Small Homes)

One of the most reliable boilers in the UK
  • Efficiency: 93% ErP rating
  • Output Range: 25kW–30kW
  • Dimensions: 700(h) x 300(d) x 400(w)
  • Warranty: 7 years standard

The Worcester Bosch Greenstar 2000 is an excellent choice if you have a small home and are looking for an industry-leading boiler at a competitive price.

It’s the brand’s quietest model and perfect for small homes with one bathroom thanks to its compact size. The Greenstar 2000 is Quiet Mark certified and can seamlessly fit between your cupboards without sticking out.

With an ErP rating of 93%, the Greenstar 2000 is a super-efficient workhorse that comes in 25kW and 30kW power outputs (sizes).

It’s hydrogen-ready and you get a 7-year parts and labour guarantee when fitted with a system filter. It also comes with a 10-year guarantee on the primary heat exchanger for added peace of mind.

Hydrogen ready: Can operate on a hydrogen and natural gas mix and if the government boosts “green gases” in the UK gas grid, you can trust the boiler will continue working without needing a complete switch to another boiler in the future.

The Greenstar 2000 features a user-friendly digital display and comes in an ultra-modern design with easy-to-remove side panels for convenient maintenance and servicing.

It’s an ideal choice if you’re on a budget and offers perks you can expect from a premium brand while keeping your hot water and heating running reliably all year round.

Why do we think the Greenstar 2000 is an excellent option?

  • Which? Best Buy Award
  • A swanky exterior design combined with a powerful, efficient, and reliable interior. 
  • Planet-friendly packaging that’s great for your home and the environment

Valliant EcoTEC Pro 28 (Best Reliable Boiler for Large Homes)

  • Efficiency: 89.3% ErP rating
  • Output Range: 24kW–30kW
  • Dimensions: 720(h) x 440(d) x 338(w)
  • Warranty: Up to 10 years

The Valliant EcoTEC Pro 28 is a popular model known for its reliability and high quality. It’s a modern A-rated combi boiler with an energy efficiency of 89.3% and a solid reputation among customers and installers.

The Vaillant EcoTEC Pro 28 is available in different sizes, including 24kW, 28kW and 30kW. Hot water flow rates range from 9.6 l/min up to 12.3 l/m and can ensure you get a fair amount of pressure and capacity in small to medium-sized flats and properties. 

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The boiler is super simple to use thanks to the bright LCD display and you can be sure of a quiet operation guaranteed by the Quiet Mark award. The EcoTEC Pro is also installed with Vaillant’s vSMART technology which helps it adapt to the way you use your heating.

You’ll also get a range of features, including weather compensation that enables you to save money on your heating bills and reduce energy waste. 

The stylish display also offers information like the pressure, temperature of water in the flow pipes, and fault codes if a component needs to be replaced, or your boiler needs servicing.

The Valkliant EcoTEC Pro 28 comes with a standard 5-year warranty but you can extend it to 10 years if you use a Valliant Advanced Installer for the installation.

Why do we think the Valliant EcoTEC Pro is an excellent option?

  • Hand-built in Derbyshire, UK
  • Good performance and full marks in categories like ease of repair, availability of parts and spares, and efficiency. 
  • Smart technology allows you to control your heating and hot water from your smartphone.

How Should You Choose A Combi Boiler?

Combi boilers are very popular these days as they are compact and efficient units that provide both heating and hot water without the need for a water tank.

There are a range of factors that will need to be considered when choosing a combi boiler, including the following:

  • The size of the property including the number of bathrooms.
  • The number of residents.
  • The water pressure available in your area.
  • The amount of space available for the boiler unit itself.

Combi boilers are most suited to smaller residential properties with only 1-2 bathrooms. If the property size is bigger than this some combi boilers may struggle with water pressure issues when, for example, more than one bath or shower is being utilised at the same time.

Another factor when looking to install a combi boiler is what existing heating system is in place.

For example, if there is a back boiler or water tank in place, these would need to be decommissioned and removed, which will increase the costs of a new boiler installation.

Also, if there are changes required to the system pipework, there would be further additional costs.

Straight-forward boiler installations, for example, installing a like-for-like combi-boiler in a smaller residential property, could be fairly easy to organise via an online boiler supplier.

However, where there are changes required as discussed above, it would be worth seeking the advice of a qualified heating engineer in order to get an accurate assessment.

Did you know the efficiency of your boiler can impact the amount of energy it uses and ultimately impact your heating bill costs? Check out our guide to the best condensing boilers if you are interested to find out more. 

You may also find our review of the best eco-friendly boilers of interest.

Who offers the best boilers deals in the UK? Check out our review of online boiler installation companies, boiler brands and the best UK boilers that topped our list concerning new boilers in the current year.

Which are the Best Combi Boiler Brands?

In order to shortlist our top three combi-boiler recommendations, we have compared the following factors:

  • Boiler warranty length is offered by the manufacturer.
  • The overall brand’s reputation.
  • Previous customer reviews on platforms such as Trustpilot.
  • Boiler price ranges and value for money.
  • Boiler specifications and performance.
  • Energy efficiency ratings.
  • Reliability levels, calculated from the numbers of issues raised with recently fitted boilers.
  • Brands that receive the most industry awards.
  • Customer aftercare service performance.

#1 Viessmann Combi Boilers (Best)


Our second position goes to Viessmann, a German boiler manufacturer that has been dominating the European boiler market for some time and is now growing in popularity within the UK too.

Viessmann produces high-quality boilers at competitive prices and also offers long product warranties also.

The Viessmann boiler model that we would recommend is the Vitoden 050-W gas combi-boiler.

This popular and award-winning boiler model is available in two different power output options and produces low CO2 emissions while having an A-rated energy efficiency score.

  • Warranty period: up to 10 years.
  • Hydrogen-ready? Yes.
  • Stainless steel heat exchanger? Yes.
  • Plastic components or rubber? Latest 2022 models – no.

How old is your boiler? Should you consider a boiler repair or start looking at the latest boiler prices? It’s no secret that boiler efficiency deteriorates over time.

See also  What is ERP? A Complete Guide to Boiler Ratings

#2 Worcester Bosch (2nd Best Combi Boilers)

Worcester Bosch Boilers

Our first position goes to Worcester Bosch who are well-established UK brand that produces prestigious and sought-after boilers.

The company has a great reputation within the boiler industry for producing quality boilers, and they have even won awards along the way while also providing a high level of customer service and aftercare to their customers.

Worcester Bosch manufactures a wide range of boilers, across most boiler types and keeps good availability of parts should replacements be required.

Got a common boiler problem? Check out our quick-fix guide on boiler lockoutboiler ignition faultsboiler PCB faultsfaulty diverter valves, and boiler timer issues.

In addition, the company is well-known for offering long product warranties, sometimes up to 10 years, which provides additional reassurance and peace of mind.

Worcester Bosch boilers do often price up as a little more expensive than some of the competitor models. However, as we have seen, the benefits of the quality of the boiler and after-sales provided, position Worcester Bosch as our top recommended boiler manufacturer.

The brand receives great reviews online and has a great reputation for reliability as well as energy efficiency.

Its all-round best choice in 2024 is the Greenstar 4000 combi-boiler. It’s available in two options of power output, the 25kW and 30kW, and yet is compact in size and has easy to use simple controls. The right size for you will depend on the requirements of your property or household.

What size boiler is right for your home? If you are thinking about a combi boiler, it is largely determined by the number of radiators in your home.

Check out our complete guide to new boiler installation here if you are wondering about the best type of boiler for your home. 

#3 Alpha Innovation Boilers (3rd Best Combi Boilers)


Alpha Innovation is relatively new in the UK domestic gas boilers market. However, they’ve quickly established themselves as a reliable and excellent choice, especially when you consider their price point.

For example, some of the leading boiler manufacturers do not use all metal components or a more durable stainless steel heat exchanger, but Alpha does, yet is more affordable, so it definitely deserves some kudos for that achievement.

Their most popular gas boiler is the Alpha E-Tec, which typically comes with a 5 year warranty, but if you buy it from one of the boiler installation companies online, like Heatable, you can secure a very generous 10 year warranty.

  • Warranty period: up to 10 years.
  • Awards: Good Homes Magazine approved (2021 only).
  • Hydrogen-ready? Some models.
  • Stainless steel heat exchanger? No, aluminium.
  • Plastic components or rubber? Some models do.

Check out our boiler brand price guides and comparisons:

#4 Vaillant Boilers (4th Best Combi Boilers)


Vaillant is granted our third place for boiler manufacturer recommendations and is an award-winning German company that produces high-quality and highly efficient boilers.

In addition to the standard of the boiler, Vaillant also offers long product warranties and has good availability of parts should replacements ever be required.

The Vaillant combi-boiler model that we would recommend is the ecoTEC Pro.

Similar to our other combi-boiler recommended, this model also comes in two output options depending on the property and household requirements. However, the options are more powerful than the rival brands, which makes this combi-boiler suitable for slightly larger properties or households with higher hot water demands.

In order to achieve the powerful results from the ecoTech Pro, high water pressure on the property will be required.

As the name suggests, the model is more eco-friendly than others available on the market and is built using 85% recycled materials, as well as securing an A-rated energy efficiency score.

Recommended reading: 

Best Combi Boiler Summary

We appreciate that the boiler market can appear crowded at first glance. However, hope that this guide has helped simplify the options by summarising the top combi-boiler manufacturers, as well as exploring each brand’s most celebrated boiler models.

When assessing our recommendations, we reviewed the brand’s reputation, customer reviews, boiler prices as well as other factors such as the warranty lengths offered by the manufacturer.

Sources and References


Further reading: