System Boilers

Keep hot water flowing with our range of gas system boilers. Designed for properties with a separate hot water cylinder, system boilers are a reliable choice for homes with higher water demand or multiple bathrooms. These boilers house key components inside the unit, making installation quicker and reducing the need for external tanks. We stock gas boilers from trusted brands like Baxi, Worcester, Intergas and more – they’re efficient, easy to fit, and built for long-term use.  Complete your system boiler system install with our range of flue kits, cylinders and heating controls.

Q: What is a gas system boiler, and how does it work?

A: A gas system boiler heats water for your central heating and stores hot water in a separate cylinder. Unlike heat only boilers, system boilers don’t need a cold water tank as they take water from the mains - all key components are built in. That makes them quicker to install and more compact than older-style setups, while still supporting high hot water demand.

If you’re upgrading an older boiler system but want to keep the hot water cylinder, a system boiler offers a great solution.

Q: Who should choose a system boiler over a combi boiler?

A: A system boiler is ideal for homes that:

• Use lots of hot water across multiple taps or showers

• Already have a cylinder-based setup

• Have low mains water pressure that doesn’t suit a combi boiler 

Combi boilers are better suited for smaller homes with one bathroom and less simultaneous demand.

Q: What output size system boiler do I need?

A: 

• 12–15kW: Flats or small homes with 1 bathroom

• 18–24kW: Medium homes with 2 bathrooms

• 30kW+: Large homes or households with high hot water use

We always recommend checking with a heating engineer to size your boiler correctly based on radiators, insulation, and hot water needs.

Q: What is a sealed system boiler?

A: Sealed system boilers are closed-loop systems that operate without open vent tanks in the loft. Most modern system boilers fall into this category – they’re pressurised and self-contained, offering greater efficiency and less risk of contamination or freezing.

Q: Are system boilers available in compact models?

A: Yes, there are plenty of compact system boilers available, designed to fit inside kitchen cupboards or tight airing cupboards. These are ideal for smaller homes or flats that still need cylinder-fed hot water. Some great options include:

• Intergas Compact System Boiler

• Baxi Megaflo Compact System Boiler

• Worcester Greenstar Compact System Boiler

Q: How much do gas system boilers cost?

A: Prices depend on brand, size and spec. As a guide:

• Entry-level boilers start from around £700 to £800

• Higher spec models with smart controls or longer warranties can cost £1,200–£1,500+

Check out our range for exact pricing. But remember, whenever costing up a new boiler, also take into account the labour costs and any costs for flue kits, cylinders or controls too. 

Q: Do you supply LPG-compatible system boilers?

A: Yes, we supply LPG-ready models and LPG conversion kits for select system boilers, ideal for off-grid homes without access to mains gas.

Q: Do you offer delivery on gas system boilers?

A: Yes, we offer UK-wide delivery on all system boilers, with click & collect available at your local JT Atkinson branch. For trade quantities or project support, speak to our team for advice and bulk availability.