What is a System Boiler?
A system boiler is a popular heating solution for medium to large-sized homes, particularly those with multiple bathrooms, where several people may be using showers or taps simultaneously. Unlike combi boilers, which heat water on demand, a system boiler works with a separate hot water storage cylinder to supply a steady flow of hot water throughout the home. However, unlike traditional heat-only boilers, it doesn’t require a cold water tank in the loft, making it more compact and easier to install.
One of the biggest advantages of a system boiler is its ability to deliver strong hot water pressure to multiple outlets at the same time, making it ideal for a home with a high hot water demand. It also offers greater energy efficiency, particularly when paired with an insulated cylinder or renewable technologies like solar thermal. They’re also more future-proof and offer better integration with modern smart controls and zoning.
How does a System Boiler Work?
A system boiler takes water directly from the mains supply, heats it internally, and stores the heated water in a dedicated hot water cylinder, ready for use when needed. The cylinder is usually kept in an airing cupboard or similar space within the home. When you turn on a tap or shower, the system draws hot water from the cylinder, not directly from the boiler itself. The stored hot water ensures consistent availability during peak usage times, and the mains connection allows for reliable water pressure throughout the house.
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Vaillant System Boilers
Vaillant is a leading European HVAC manufacturer with over 150 years of expertise in innovative, energy-efficient heating solutions. Committed to sustainability, Vaillant harnesses environmental energy to heat homes efficiently and responsibly. Their product range includes eco-friendly boilers, advanced heat pumps, and integrated smart home systems designed to reduce environmental impact while maintaining comfort.
EcoTEC Plus System Boiler
This boiler boasts a range of outputs from 12 kW to 37 kW, and high-output models up to 64 kW. It features A-rated efficiency, a stainless-steel heat exchanger, and Quiet Mark approval. With smart modulation, weather-responsive controls, and a compact design, it suits homes with multiple bathrooms. A 5-year warranty comes as standard, extendable to 10 years with an approved installer.
ecoTEC Exclusive (Green iQ) System Boiler
Delivering around 27 kW of output, this boiler is designed for top-tier energy efficiency. Made with 85% recyclable materials and Quiet Mark approved, it combines sustainability with quiet operation. It’s smart-ready, fully compatible with Vaillant’s vSMART control system, and comes with up to a 10-year warranty when installed by a Gas Safe-registered installer.
ecoFIT Pure System Boiler
This boiler offers outputs from 12 kW to 30 kW and is designed with a compact build to fit neatly into kitchen cupboards. It is Quiet Mark certified for low noise and delivers A-rated efficiency at 94%, with durable stainless steel components. It includes a 2-year standard warranty, extendable to 10 years with a Gas Safe-registered installer.
Worcester Bosch System Boilers
Worcester Bosch is a top boiler manufacturer recognised for producing reliable, energy-efficient heating systems. Known for their high-quality craftsmanship and cutting-edge technology, their boilers deliver exceptional performance and long-lasting durability.
Greenstar i System (9-30 kW)
Worcester Bosch’s popular, compact system boiler is typically installed in medium to large homes. It offers A-rated efficiency (92-94%), has a cupboard-fit design, and has up to 7 years warranty, and solar thermal compatibility.
Greenstar 4000 System (12-24 kW)
This quieter, smarter mid-range boiler offers A-rated (94%) efficiency and a 10-year warranty with an accredited installer. With noise levels around 42 dB, it’s ideal for small to medium homes with 1 to 2 bathrooms.
Greenstar 8000 Life/System (30-50 kW)
A 30kW system boiler and above is designed for larger homes with high hot water demand. It offers A+ (94%) efficiency, up to a 12-year warranty with an accredited installer, and features like weather compensation and Bosch EasyControl compatibility, perfect for properties with multiple bathrooms or greater heating needs.
Ideal System Boilers
Ideal is a well-established and respected British boiler brand with over a century of experience. Renowned for reliability and innovation, Ideal boilers deliver excellent performance and strong value for money.
Ideal Vogue Max System Boiler
Offering a premium performance with outputs from 15 to 32 kW, this boiler also has A-rated efficiency and a compact design. It features a magnetic system filter and full text fault codes, with a 10-year warranty, extendable to 12 years via accredited installation.
Ideal Logic Max System Boiler
A popular, well-priced, and reliable choice, known for its compact cupboard-fitting design. It offers outputs from 15 to 39 kW, A-rated efficiency, frost protection, a backlit digital display, and a built-in service reminder. Warranty ranges from 7 to 10 years, depending on installation.
Ideal Logic+ System Boiler
A reliable mid-range option, the Logic+ offers A-rated efficiency and outputs from 15 to 30 kW, making it suitable for various home sizes. Its compact design, built-in frost protection, and easy-to-use digital display make it a practical and user-friendly choice. It includes a 7-year warranty, extendable to 10 years with accredited installation.
What Size System Boiler Do I Need?
System boilers come in various sizes, measured in kilowatts (kW), to match the differing heating and hot water needs of homes. Below is a list of sizes and our recommendations for the type of home each is best suited for:
12-18 kW: At the lower end of kW, this size boiler is perfect for small homes or apartments with one bathroom, providing sufficient heating and hot water without wasting energy.
- 18-24 kW: This size is best suited to medium-sized homes with one or two bathrooms, balancing performance and efficiency.
- 24-30 kW: Best for larger homes with multiple bathrooms or higher hot water demand, ensuring consistent supply and comfort.
- 30 kW and above: Boilers with a higher kW, such as 30 kW and above, are designed for large properties or homes with several bathrooms, offering powerful heating and hot water capacity to meet heavy usage.
How Much Does it Cost for a System Boiler and Installation?
The cost of a new boiler installation depends on the type of system, your home’s setup, and your chosen brand. A straightforward combi-to-combi replacement with a high-quality Worcester Bosch boiler (including a 5-year guarantee) typically starts from around £1,950.
When you book with us, our expert engineers provide a complete, hassle-free service, from installing the boiler in a location that suits your home to connecting it to your heating and water systems. We’ll also integrate any smart controls if desired, and carry out full safety testing to ensure everything is running efficiently and reliably.
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