Best System Boilers for 2024

Are you looking at having a new system boiler installed in your home but aren’t sure which model is right for you? Fear not!

In this guide, we’ll be listing the best system boilers in 2024, taking an in depth look at their key features, power outputs available and much more!

We also have an in depth article available on the best boiler brands.

We’ll be scoring each system boiler out of five stars on the following:

• Quality & Technology

• Efficiency

• Warranty

• Price

• Customer Ratings & Awards

We’ll then use these to calculate an overall percentage score for each boiler!

So, if you want to find out which system boilers are best for your home in 2024, keep reading!

Best System Boiler Brands in the UK

#1 Worcester Bosch

In first place comes market leader, Worcester Bosch. This household name has been keeping UK homes warm since 1962 and is committed to delivering the highest standard of heating.

Worcester Bosch offers a wide range of combi, regular and system boilers that can integrate seamlessly into your home, whilst also helping you to save money on your heating bills thanks to their high efficiency ratings.

It’s no surprise that Worcester Bosch is an eleven time winner of the Which? Best Buy award, with Which? claiming:

“Worcester Bosch performs so consistently well in our annual reliability surveys that its name is synonymous with dependability.”

Best System Boilers Available from Worcester Bosch

Worcester Bosch Greenstar 4000 System 98%

The Worcester Bosch Greenstar system boiler is one of the brand’s latest and greatest innovations, taking the place of the classic Greenstar i, Worcester’s previously best selling boiler.

Sat between the 2000 and 8000, the Greenstar 4000 system boiler is the perfect mid-range boiler for any small to medium sized home. Let's take a look at some of its key features:

Worcester Bosch Greenstar 4000 System Quality & Technology 4.5/5

With a brand new modern design, an easy to use full colour text display and super quiet operation, the Worcester Bosch 4000 system is built with high quality in mind.

Its curved edge casings and sleek digital display make it stand out from the crowd of plain and boring boilers, making it much more attractive in your home.

Some great technology features of the Worcester Bosch 4000 system include the Bosch EasyControl for wireless connectivity and the intelligent filling system, a software that is able to maintain your boiler’s pressure at optimum level. 

If the boiler pressure drops, the internal filling valve gets to work to automatically refill the system  as well as alerting you if too much pressure has been lost, so you can top it up manually instead of having to arrange an engineer callout.

The only slight downside of this system boiler is that Worcester Bosch only offers aluminium heat exchangers across their entire range. 

Although aluminium heat exchangers work incredibly well thanks to their high thermal conductivity, they aren’t as durable or high quality as stainless steel heat exchangers, which are much stronger and more corrosion resistant thanks to the added chromium.

Worcester Bosch Greenstar 4000 System Efficiency 5/5

Thanks to the Greenstar 4000’s 94% A-rated energy efficiency, you can expect to see incredible savings on your home energy bills whilst also reducing your carbon footprint- all without changing the amount you heat your home!

Worcester Bosch Greenstar 4000 System Warranty 5/5

The Greenstar 4000 comes with a guarantee of up to 10 years, depending on the engineer that installs it.

At iHeat, all of the boilers we install, including the Greenstar 4000, come with a 10 year warranty on parts and labour, so you can rest easy knowing you’re covered should something go wrong that isn’t your fault.

Worcester Bosch Greenstar 4000 System Price 5/5

As we mentioned earlier, the Worcester Bosch Greenstar 4000 system boiler is a perfect mid-range boiler, meaning it isn’t the cheapest boiler available on the market, nor is it the most expensive. 

Worcester Bosch boilers do tend to be on the slightly pricier side, however, the extra cost is well worth it thanks to their incredibly reliable heating, high quality and energy efficiency which can help you cut your energy bills significantly.

Worcester Bosch Greenstar 4000 System Customer Ratings and Awards 5/5

The Worcester Bosch Greenstar 4000 system boiler has replaced the Greenstar i as the brand's best selling system model, so it’s no surprise that it was recognised as a Which? Best Buy after being highly recommended by owners of the model.

Which Size Worcester Bosch Greenstar 4000 System is Right for My Home?

Score

• Quality & Technology: 4.5/5

• Efficiency: 5/5

• Warranty: 5/5

• Price: 5/5

• Customer Ratings and Awards: 5/5

Overall Score: 24.5/25

Overall Percentage: 98%

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Worcester Bosch Greenstar 8000 Style System 94%

The Greenstar 8000 Style is Worcester Bosch’s premium system boiler, sitting at the top of the range. 

With an incredibly sleek design, powerful heating and advanced technology to help keep your heating costs down, this is a system boiler designed to integrate into any home.

Worcester Bosch Greenstar 8000 Style System Quality & Technology 4.5/5

The Worcester Bosch Greenstar 8000 has been built with only the highest quality in mind. With a super sleek design available in either black or white, this is an incredibly stylish system boiler.

The Worcester Bosch 8000 Style features a range of innovative technology designed to maximise comfort and optimise heating and hot water performance.

When paired alongside Bosch’s EasyControl, the 8000 Style can be effortlessly controlled from anywhere, giving you total control over your home’s heating and hot water no matter where you are.

Compatible with Amazon Alexa and Google Assistant, you can even control your heating with your voice!

Worcester Bosch Greenstar 8000 Style System Efficiency 5/5

Thanks to the 8000 Style’s 94% A-rated energy efficiency, this system boiler has the potential to help you make incredible savings on your home energy bills without changing the amount you heat your home!

Worcester Bosch Greenstar 8000 Style System Warranty 5/5

The Greenstar 8000 Style comes with a guarantee of up to 10 years, depending on the engineer that installs it.

At iHeat, all of the boilers we install, including the Worcester Bosch 8000 Style, come with a 10 year warranty on parts and labour, so you can rest easy knowing you’re covered should something go wrong that isn’t your fault.

Worcester Bosch Greenstar 8000 System Price 4/5

Due to all of the fantastic features and premium design of the 8000 Style, it is on the pricier end, starting at around £2,585 at iHeat for the boiler plus install. 

The extra cost is well worth it for those wanting a high quality ultra sleek system boiler with incredibly reliable heating and energy efficient technology which can help you cut your energy bills significantly.

Worcester Bosch Greenstar 8000 System Customer Ratings and Awards 5/5

The Greenstar 8000 Style system is another Worcester Bosch system boiler that has been recognised as a Which? Best Buy after being highly recommended by owners of the model and receiving a brand score of 84%.

Which Size Worcester Bosch Greenstar 4000 System is Right for My Home?

Score

• Quality & Technology: 4.5/5

• Efficiency: 5/5

• Warranty: 5/5

• Price: 4/5

• Customer Ratings and Awards: 5/5

Overall Score: 23.5/25

Overall Percentage: 94%

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#2 Viessmann

In second place comes the family-owned German boiler brand Viessmann. This brand has taken the European market by storm thanks to their range of high quality yet affordable heating solutions. 

Awarded Which? Best Buy for the fourth time in 2021, it’s clear Viessmann is a brand you can trust.

Best System Boilers Available from Viessmann

Viessmann Vitodens 100-W System Boiler 98%

The Viessmann Vitodens 100-W System is efficient, compact, quiet and affordable, making it the most popular system boiler available at iHeat.

Viessmann Vitodens 100-W System Boiler Quality & Technology 5/5

The Vitodens 100-W System boiler features innovative technology and services combined with reliability and longevity and comes ready for smart technology, helping you to optimise your heating and save on energy costs. 

Viessmann are leading the way by using a Stainless Steel heat exchanger in all of their boilers, with excellent corrosion resistance through high grade stainless steel. 

This is a fantastic alternative to aluminium, maximising the boiler’s lifespan so you can count on it for years to come.

Viessmann Vitodens 100-W System Boiler Efficiency 5/5

Thanks to the Vitodens 100-W’s 94% A-rated energy efficiency, you can expect this system boiler to help you make incredible savings on your home energy bills without changing the amount you heat your home!

Viessmann Vitodens 100-W System Boiler Warranty 5/5

At iHeat, all of the boilers we install, including the  Viessmann Vitodens 100-W, come with a 10 year warranty on parts and labour, so you can rest easy knowing you’re covered should something go wrong that isn’t your fault.

Viessmann Vitodens 100-W System Boiler Price 5/5

For such a high quality system boiler, the Viessmann Vitodens is surprisingly affordable. This is a significant factor that contributes to their growing popularity across the UK.

Viessmann Vitodens 100-W System Boiler Customer Ratings and Awards 4.5/5

Thanks to all of its great technology and high quality components at an affordable price, the Vitodens 100-W has been voted a Which? Best System Boiler a number of times over the last few years.

Due to being a relatively new brand in the UK market, it hasn’t had as much recognition as bigger household names like Worcester Bosch, however they’re soon catching up and are currently a main competitor.

Which Size Viessmann Vitodens 100-W System Boiler is Right for My Home?

Score

• Quality & Technology: 5/5

• Efficiency: 5/5

• Warranty: 5/5

• Price: 5/5

• Customer Ratings and Awards: 4.5/5

Overall Score: 24.5/25

Overall Percentage: 98%

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Viessmann Vitodens 200-W System Boiler 86%

The Viessmann Vitodens 200-W is similar to the Vitodens 100-W, except it is much more powerful and comes with more bells and whistles.

Viessmann Vitodens 200-W System Quality & Technology 5/5

The Vitodens 200-W System boiler features all the same innovative technology and services as the 100-W with added features such as the Lambda Pro Plus combustion controller, MatriX-Plus burner for greater efficiency and less nitrogen oxide for a more environmentally responsible operation and lower energy bills.

This boiler also comes with an integrated WiFi interface for internet connection, allowing you to connect to your boiler via the ViCare app and control your heating from your phone.

Viessmann Vitodens 200-W System Efficiency 5/5

Thanks to the highly efficient MatriX-Plus burner, the Viessmann Vitodens 100-W system boiler converts up to 98% of the fuel into heat. 

This gives it an energy efficiency rating of A, so you can save on your bills- an essential in the current cost crisis!

Viessmann Vitodens 200-W System Warranty 3/5

As standard, the Vitodens 200-W has a 3 year warranty, however this is increased to 5 years when installed by a trained installer.

Viessmann Vitodens 200-W System Price 4/5

One of the biggest differences between the Vitodens 10o-W and 200-W is the price. The 200-W can range between £500-£1,000 more expensive than the 100-W depending on where you buy it from.

The stark difference in price is due to the different components inside the boiler. The 200-W comes with much higher quality and efficient technology and doesn’t require as many accessories as the 100-W (which can often add up in cost).

For the technology you receive with the 200-W, the price is great, however  most homeowners simply won’t require all of the additional technology, making the 100-W a better and more affordable option.

Viessmann Vitodens 200-W System Customer Ratings and Awards 5/5

Thanks to all of its fantastic technology and high quality components, the Vitodens 200-W has been voted a Which? Best Boiler 2021.

Which Size Viessmann Vitodens 100-W System is Right for My Home?

System boilers, like this one, are usually installed in medium to large modern homes with multiple bathrooms, where there’s more demand for hot water. 

They’re particularly good if you live in an area with poor water pressure ideal for detached houses, semi-detached houses and apartment buildings.

Score

• Quality & Technology: 5/5

• Efficiency: 5/5

• Warranty: 3/5

• Price: 4/5

• Customer Ratings and Awards: 4.5/5

Overall Score: 21.5/25

Overall Percentage: 86%

Get a quote

#3 Alpha

With over 50 years’ experience in the heating industry, Alpha has a wealth of knowledge when it comes to combining traditional values with an innovative approach to providing the highest quality products and services.

Alpha prides itself on offering heating and hot water solutions at an affordable price without compromising on quality, allowing customers to heat their homes whilst cutting their energy bills.

Best System Boiler Available from Alpha

Alpha E-Tec S 92%

The Alpha E-Tec S is one of our most popular system boilers at iHeat due to its high quality and great affordability. 

Alpha E-Tec S Quality & Technology 5/5

The entire E-Tec range features brand new stainless steel heat exchangers and zinc plated expansion vessels, making them highly robust, more corrosion resistant and much longer lasting.

Taking these extra steps to maximise the longevity of your boiler life is what makes this range stand out against its competitors, who mostly use aluminium heat exchangers.

The E-Tec also has a high-efficiency pump which helps to deliver impressive hot water flow ratings and the single electrode drive charge is very easy to access, meaning your boiler will be easy to control and manage after installation.

Alpha E-Tec S Efficiency 5/5

The Alpha E-Tec S is incredibly efficient, converting up to 93% of fuel into heat, giving it an energy efficiency rating of A.

Alpha E-Tec S Warranty 5/5

As standard, the Alpha E-Tec S comes with a 7 year warranty, however, at iHeat, all of the boilers we install, including the Alpha E-Tec S, come with a 10 year warranty on parts and labour, so you can rest easy knowing you’re covered should something go wrong that isn’t your fault!

Alpha E-Tec S Price 5/5

Alpha is one of the most affordable boiler brands on the market which can sometimes put people off as they worry about their quality and reliability.

However, the E-Tec S has plenty of high quality components and with a 10 year warranty with iHeat, you can count on this boiler to last you into the future.

Alpha E-Tec S Customer Ratings and Awards 4/5

As Alpha is a lesser known brand, it hasn’t received many awards, however according to Which?, owners of Alpha boiler models are generally happy with them and gave them a ⅘ score on reliability.

Which Size Alpha E-Tec S is Right for My Home?

Score

• Quality & Technology: 5/5

• Efficiency: 5/5

• Warranty: 5/5

• Price: 4/5

• Customer Ratings and Awards: 23/5

Overall Score: 21.5/25

Overall Percentage: 92%

Get a quote

System Boilers Frequently Asked Questions (FAQ)

What is a System Boiler?

A system boiler works by directly providing heat to your central heating and hot water system through a storage cylinder. 

This kind of boiler works similarly to a conventional or standard boiler, as both types need to store hot water that can be used throughout the house. However, there are some key differences between the two.

Unlike regular boilers, a system boiler takes water directly from the system in your home.

This makes them a more compact system than regular boilers, while still being able to provide a high volume of hot water, making them highly versatile.

(YouTube explaining different types of boilers)

Should I Convert from a Combi to a System Boiler?

Generally, if you have already had an older boiler converted into a combi, you wouldn’t convert back to a system boiler, however, there may be some instances where this is required.

For example, if a combi boiler has been installed in a large property that has a very high demand for hot water often, this wouldn’t be suitable and would likely need converting to something which can power two water sources (such as a shower and a tap) at the same time.

What Size (kW) System Boiler Do I Need?

When we talk about boiler size, we’re often referring to the output in kilowatts (kW) as opposed to the physical dimensions of the boiler itself.

Generally the bigger the home the bigger kW combi boiler you will need. Check out the table below to find out which size system boiler is best for your home!

New System Boilers at iHeat

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