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System Boilers Guide

//System Boilers Guide

System Boilers Explained

System boilers are similar to regular boilers as they both store hot water, however for a system boiler, the water is supplied directly from the mains. A system boiler generates heat for the central heating system and hot water for storage, in either cylinder or tank. This type of boiler is a great option if you have a large home or high hot water demand. An A-rated condensing system boiler will convert more than 90% of the fuel into heat, reducing your overall heating bills.

What is a System Boiler?

A system boiler includes additional components in the boiler, compared to that of a regular boiler.  An expansion vessel is also required for the vented hot water systems and safety features, such as Pressure Release Valve (PRV). They take the water supply directly from the mains, heat the water to supply it to radiators and store it in a hot water cylinder or tank.

Hot water cylinder / tank

As a system boiler generates hot water and requires a hot water cylinder for storage, the hot water cylinder allows hot water to be vented at multiple sources, e.g. taps, showers, without losing any pressure. (The hot water tank needs to be insulated to prevent heat loss).

System Boiler installation

System boiler installations are easier than regular boilers as many of the individual components of heating system and hot water system are built inside the boiler. The unit is compact in size and only requires a tank.

Benefits of System Boilers

  • Compact in size and requires a cylinder.
  • Uses a tank to store hot water so the hot water can be accessed through multiple taps at the same with without losing pressure.
  • Stronger water pressure, as water is supplied directly from the mains
  • No cold-water tank is needed
  • Compatible with solar thermal solutions

Things to consider

  • Need space for the storage of the hot water tank
  • Size of hot water tank
  • No instant hot water. If you run out of water in the tank, system boiler will have to heat water and fill the tank before you can access hot water.
  • More expensive than combi boilers due to additional cost of the hot water tank

Cost of a System Boiler

There are many models and brands available on the market that comes with different prices. Prices start from about £1800 for a system boiler.

Best System Boilers

There is wide range of system boilers available in the market and below are some of the Best System Boilers. System boiler prices depends on various brands and output.


ManufacturerModelSize (output)Efficiency
Worcester Bosch boilerGreenstar system i9KW to 24KW94%
Vaillant boilereco Tec Plus 12KW to 37KW89%
Baxi boilerMegaflo system15KW to 32KW88.6%
Viessmann boilerVitodens 200-W19KW to 35KW89.2%
Intergas boilerHre SB18KW to 40KW89.2%

These boilers are rated highly buy the users and recommended by local trusted engineers. A gas safe engineer should be able to recommend you a best system boiler suited for your home.

 System Boiler Prices

System boiler prices and boiler installation cost depend on various things. Prices range anywhere between £500 – £2000 and you should consider extra for boiler installation cost. Here’s a guide for best system boilers 2018.

ManufacturerModelStandard warrantyAverage Price
Worcester Bosch boilerGreenstar system i7 years£900 – £1200
Vaillant boilereco Tec Plus7 years£950 – £1300
Baxi boilerMegaflo system7 years£750 – £1250
Viessmann boilerVitodens 200-W5 years£950 – £1200
Intergas boilerHre SB7 years£850 – £1200