What Is a System Boiler and How Much Do They Cost?

Thinking about buying a new system boiler? The WhatPrice team has gathered the latest data on system boiler prices, plus all of the key information you need to make an informed purchase decision. 

Introduction to system boilers

A system boiler stores hot water in a storage cylinder, allowing you to access hot water at any time so long as the tank isn’t depleted. Since the hot water is stored, it can provide more powerful hot water capabilities which can best meet the demands of properties with multiple bathrooms. 

Unlike a regular boiler, a system boiler doesn’t require a separate tank in the loft as the boiler takes the water directly from the mains. The hot water cylinder is also compact enough to fit in an airing cupboard, which can also work to free up space elsewhere in your home. 

Besides having a larger family, switching to a system boiler is ideal if replacing your existing combi boiler still wouldn’t meet your hot water and heating demands. 

Best system boilers

Before we break down the average system boiler cost, it’s worth highlighting some of the best system boilers on the market. 

In short, considering any of the following system boilers will likely result in the maximum user satisfaction in terms of performance, energy efficiency and overall reliability. 

Worcester Bosch Greenstar 8000 Life

Complete with technology that’s unique to Worcester Bosch (one of our top boiler brands), it incorporates a ‘Greenstar Intelligent Filling System’, which automates the boiler pressure to reduce the need for engineer visits. 

As a user, you’ll also find the intuitive LCD display simple to operate, including if you need any diagnostic codes to enable a swift repair of your boiler. 

If installed by an approved technician, you can enjoy one of the longest warranty periods we’ve found for any system boiler – a whopping 12 years! 

Viessmann Vitodens 100-W System

Getting access to the boiler can be a common issue for boiler installations and servicing. However, the Viessmann Vitodens 100-W range ensures that all connections are easily accessible from the front. As a result, these wall-mounted boilers have a wide usage suitability for all residential properties.  

A stainless steel inox radial heat exchanger denotes premium build quality, while the integration of WiFi ensures plenty of convenience for the modern household. 

Vaillant ecoTEC Plus System

Similar to other Vaillant boilers, the company will extend your warranty for up to 10 years if the boiler is installed by one of their Vaillant Advanced technicians. 

As is standard for Vaillant, there is an unrivalled level of choice when it comes to choosing a boiler size, which can ensure you get exactly what you need to power your heating and hot water. 

Along with having a quiet operation, Vaillant ecoTech boilers also come hydrogen-ready, which can help future-proof your new boiler purchase. 

Ideal Vogue Max System

User-friendliness is a staple feature of the Ideal system boilers, as the Vogue Max range features a 3.5 inch colour LCD display allowing you to control your boiler with complete ease. 

Also included is an integrated system filter to prolong the life of your boiler. 

For those short on space, Ideal Vogue Max System boilers are designed to fit into kitchen cupboards. Although, you will still need to make room for that all-important heat cylinder elsewhere in your home. 

Baxi 800 System 2

Also included is an Adey MagnaClean Micro2 system filter which works to clean and protect your heating system from sludge and debris.

The Baxi 800 System 2 also has an external analogue pressure gauge. This allows you to monitor your boiler and top it up where needed which can reduce the need for engineer callouts. 

As one of the more modern system boilers, the Baxi 800 System 2 also comes equipped with smart thermostat technology, which enables you to control your heating remotely. 

System Boiler Prices

Brand	System boiler size	Typical boiler price (excluding installation)
Baxi	15kW	£877
Baxi	18kW	£889
Baxi	24kW	£1,011
Ideal	15kW	£1,049
Ideal	18kW	£1,089
Ideal	24.2kW	£1,147
Ideal	30.3kW	£1,174
Vaillant	12kW	£902
Vaillant	15kW	£971
Vaillant	18kW	£1,098
Vaillant	24kW	£1,227
Vaillant	30kW	£1,363
Vaillant	37kW	£1,537
Viessmann Vitodens	11kW	£1,344
Viessmann Vitodens	19kW	£1,500
Viessmann Vitodens	24.2kW	£1,550
Viessmann Vitodens	30.3kW	£1,650
Worcester Bosch	30kW	£1,317
Worcester Bosch	35kW	£1,446

When you are looking to buy a new system boiler, you should expect to pay between £877 to £1,650. This amount factors in the most popular makes and models of boilers. 

Baxi has proved to be one of the cheapest boiler brands for other boiler types, and we found that Baxi’s system boilers also proved to be the least expensive on average. 

At the other end of the scale, a 30.3kW Viessmann Vitodens system boiler will set you back £1,650 on average. This is more expensive than larger boiler sizes from other brands, including a 37kW system boiler from Vaillant costing £1,537 on average. 

Beyond the size of the boiler, the reputation of the manufacturer and warranty periods can also affect the unit cost of a boiler before installation. 

System Boiler Installation Costs

System boiler	Excluding installation	With installation	System boiler conversion
Average cost range	£877 – £1,650	£2,900 – £5,200	£4,700 – £7,000

Our research found the total cost of a system boiler with installation starts at £2,900 and can be as much as £5,200. 

However, if you are looking to convert your boiler from another type, this can add up to £2,000 onto the cost of the job. This extra cost is due to the modifications needed which require additional time and materials. 

Typically, the installer will also supply the boiler which can reduce the overall costs of the installation if they also pass on these discounts to you. That’s why you may find it cheaper to opt for a package deal from your chosen heating engineer. 

As with any purchase, it’s essential to shop around and collect at least 2-3 quotes before you go ahead. 

What else affects boiler installation costs?

Where you’re based in the UK: Similar to other work you’re thinking of getting done, tradespeople typically charge more for their services in London and the Southeast compared with the North. 

Time of year: Plumbers are typically busier in the winter months meaning they can charge more for their time. Opting to get your boiler replaced in the summer can make it cheaper, plus ensure your new boiler is up and running before the cold weather hits. 

Added job complexity: If your existing boiler doesn’t meet current building regulations, it may need to be moved which will cost more. Likewise, if your new boiler needs additional pipework or flue work, this will also add more expense onto the job. 

Accessibility: Your engineer will need good access to remove your existing boiler and install your new boiler. Difficulty reaching the required area of your home can make the job more expensive. 

💡Top tip: Find out how much homeowners in your area have paid for boiler installations by viewing their price submissions on WhatPrice.

Running costs & efficiency of system boilers

Average gas cost per hour	Average electricity cost per hour	Gas standing charge	Electricity standing charge
6.4p per kW/hr	24.5p per kW/hr	31.4p per day	60.1p per day

Finding the specific cost of heating your home can be difficult. That’s because beyond the cost of running your system boiler, how energy efficient your property is will also impact the total cost. 

However, it is possible to get a pretty close estimate by using the above figures for the average costs of electricity and gas, plus the daily standing charges. 

Our research found that system boilers are available in sizes of between 6kW and 48kW. 

So, if you have a 24 kW boiler, it will need 24 kWh* of energy for every hour your home is being heated. If the boiler is running for two hours, this will use 48 kWh. 

Based on 5 hours of usage, a 24 kWh boiler would cost £9.60 to run minus any standing charges. 

Since older boilers are known to be less efficient, switching to a newer system boiler should improve efficiency and therefore wasted energy costs.

**A kilowatt-hour (kWh) refers to one kilowatt of power for one hour. 

Advantages of system boilers

There are lots of benefits to upgrading your existing system boiler, or switching to a system boiler if your current boiler type just doesn’t cut it. 

Unlike regular boilers, system boilers are easier to install and also don’t require space in your loft. So already, this can make a huge difference if you are switching from a regular to a system boiler. 

Regardless of your current boiler type, we think you’ll also appreciate the following advantages that are most associated with system boilers. 

Better for high hot water demands

While combi boilers are popular with UK homeowners, they aren’t really designed for supplying hot water when there is a high demand. Specifically, where there is more than one bathroom in the home. 

Systems boilers store hot water in a separate cylinder. So long as the cylinder doesn’t become depleted (i.e. due to higher than normal usage), you will always have a constant supply of hot water. 

Strong water pressure

Nobody likes a shower that is so weak, it feels more like a dripping tap! Thankfully, system boilers don’t have much trouble with poor water pressure, as they are better designed to maintain a strong and consistent pressure. This is one of the many reasons why system boilers are recommended if you have multiple baths or showers in your home. 

Fantastic energy efficiency

Modern system boilers are incredibly energy efficient, with industry averages of 94% efficiency. While this is marginally less efficient than combi boilers (which have 95% average efficiency), it can still add up to huge cost savings for your energy bills. 

When you come to sell your home, having a more energy efficient boiler can also be more appealing to potential buyers. This is especially the case as energy prices continue to remain higher than in previous years. 

Leading brands available

As we’ve just covered in our system boiler cost guide above, there are some very well known names to choose from in the system boiler space. These include stalwarts such as Worcester Bosch, Vaillant, Viessmann and Baxi. 

If you are switching from another boiler type (i.e. a combi boiler to a system boiler), opting for a familiar name can give you peace of mind. It may even be the case that you can select a system boiler made by the same manufacturer as your existing boiler. 

Solar heating compatibility

Some system boilers such as Vaillant offer models that are compatible with solar technology. As well as making your home greener, this can also work to reduce your energy bills. Overall, solar heating compatibility is a great way to future-proof your heating and hot water system, especially as the government looks to move away from the current reliance on gas powered boilers. 

System boilers vs other boiler types

When comparing system boiler prices, you might also be curious to learn about the other boiler types that exist. Beyond the cost, the features and overall suitability for your property are all points to consider before you go ahead. 

Alongside system boilers, you might also be interested in combi boilers or regular boilers. We’ve highlighted some of the key features and differences below. 

System boiler vs combi boiler

Feature	Combi boiler	System boiler
Water supply	Takes water directly from the mains and heats it on demand	Draws water directly from the mains. Hot water is stored in a cylinder
Storage requirements	No tanks or cylinders required	Requires a hot water cylinder
Is loft space needed?	No	No
Efficiency	Excellent	Also excellent, although slightly less than combi boilers overall
Installation	Straightforward	Straightforward
Best for	Small to medium sized homes with one bathroom	Homes with multiple bathrooms which have high hot water demand

System boiler vs regular boiler

Feature	Regular boiler	System boiler
Water supply	Cold water storage tank	Draws water directly from the mains. Hot water is stored in a cylinder
Storage requirements	Requires both a hot water cylinder and a cold water storage tank	Requires a hot water cylinder
Is loft space needed?	Yes	No
Efficiency	Can be less efficient due to the heat loss which occurs from the tanks and pipes	More energy efficient than regular boilers
Installation	Often complex and lengthy	Typically easier due to having fewer components
Best for	Larger homes with multiple bathrooms or properties with older heating systems.	Homes with multiple bathrooms which have high hot water demand

Which boiler type is best for your home?

Stay with or switch to a system boiler if: You currently have a system boiler and it generally works well for your property and overall usage needs, it probably makes sense to go for a like-for-like swap.

A new system boiler will boast better performance and overall energy efficiency, and should also result in a straightforward installation process. 

Another benefit of a system boiler is that compared with combi and regular boilers, system boilers often maintain better water pressure. This includes when multiple demands are made at once (i.e. two showers in use at the same time).

When to choose a combi boiler: For smaller homes where the usage demands are not as high, a combi boiler might be a better fit for your property. With a combi boiler, you won’t be reliant on a hot water cylinder. There’s also no need to have a tank in the loft which can also save space. 

Choose a regular boiler: These are ideal for older properties where there is also a high demand for hot water. But, where converting to a system boiler wouldn’t be cost-effective, it would be probably best to remain with a regular boiler. 

Considerations before choosing a system boiler

There are some things to consider which may increase your new system boiler cost. In some cases, your home or user requirements may even be incompatible with a system boiler.

You’ll need a hot water cylinder: If you’re looking to replace an existing system boiler, this is less of an issue. But if you will be switching to a system boiler from another type of boiler, you will need space to accommodate a hot water cylinder. 

Space requirements: Apart from the aforementioned hot water cylinder, system boilers thankfully don’t take up too much space. But, you will need room in an airing cupboard or a similar location for the cylinder itself.

Compatibility with underfloor heating: System boilers are widely considered one of the best boilers for underfloor heating. That said, you’ll need to ensure the boiler size (kW) is compatible with the demands of underfloor heating in addition to the rest of your heating and hot water needs. 

Impact on household energy efficiency: Modern system boilers are very energy efficient, although are slightly less efficient than combi boilers overall. 

Finding a reliable system boiler installer

To ensure a safe and satisfactory boiler installation, there are a few things you’ll need to check as part of your research. 

The first place to start is the Gas Safe Register, as it’s illegal for anyone to install or work on a gas appliance unless they are on the register. 

Beyond this, we recommend choosing an installer who has accreditations related to the plumbing and heating industry, along with the likes of Trustpilot or Checkatrade.

Of course, reading customer reviews or asking for recommendations from family and friends remains as invaluable as ever. For a boiler installation especially, it’s essential that the tradesperson is not only fully qualified but also trustworthy. 

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System boiler prices FAQs

Do you have more questions about the cost of a new system boiler? 

We’ve answered some of the most queries below. For anything else, check out the rest of our boiler content where we cover everything you need to know.