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Boiler Types Explained

Knowing the ins and outs about boilers can be a confusing and often daunting task; buying a boiler is after all something homeowners usually only have to do a handful of times in their life. The type of boiler installed in your home will however make a positive difference to your lifestyle, whether that be freeing up much needed space, delivering improved flow rates to your taps and shower or providing a consistent flow of hot water. This guide outlines the core benefits of each boiler type and details the differences between them to help you to make an informed decision when buying your boiler.

Combi Boilers

A combi boiler is in effect short for a “combination” boiler. Combi boilers are incredibly popular as they are both a high efficiency water heater and a central heating boiler in a single unit that’s fed directly from the mains pressure. This therefore removes the need for a cold water storage tank and hot water cylinder, providing homeowners with enhanced living space.

As combi boilers do not store hot water, efficiency levels are usually improved as no energy is wasted in storing the water in a hot water storage tank, typically associated with heat-only and system boiler installs.

Core combi boiler benefits include:

  • Compact size makes combi boilers perfect for homes where space may be limited
  • Ideal for homes without lofts or with loft conversions, due to no cold water storage being required
  • As there’s no pipework in the loft area, the risk of pipework freezing is greatly reduced
  • Installation costs are usually less expensive as there are typically less heating components and pipework


Heat-Only Boilers

A heat-only boiler (sometimes referred to as regular or conventional) are typically found in older homes. Although older in design, regular boilers still offer great functionality and control over a home’s central heating. It’s not common to find a heat-only boiler installed in a new-build property however it is common for older homes to retain a heat-only boiler system when installing a new boiler. This is because the water provided by combi and system boilers are usually too high for an older radiator system. As such, to keep costs down when installing, many homeowners and engineers alike advise on a direct replacement.

Central heating systems with heat-only boilers installed heat stored water externally using a heating coil that’s fitted inside a hot water cylinder. The hot water cylinder is fed from a cold water cistern or the mains and a feed and expansion cistern feeds the water for the central heating system.

Core heat-only boiler benefits include:

  • Compatible with solar heating equipment
  • Ideal in areas where water pressure may be low
  • Great for homes with high and simultaneous demands of hot water


 System Boilers

A system boiler, similarly to a heat-only boiler, uses the same principles of heating stored water via a hot water cylinder. The hot water system in a system boiler install provides hot water for both water outlets and the central heating system. This means that less components and pipework are required in comparison with a regular boiler install and installation can be carried out faster and neater.

Core system boiler benefits include:

  • Added space in the loft due to a system boiler not requiring a feed and expansion cistern
  • Ability to heat two baths simultaneously
  • Economical to run
  • Built in components, making installation quick and tidy


At Direct Heating Supplies, we stock a vast range of boilers, ideal for meeting the heating needs of your home. All boilers are available with free UK delivery as standard and our customers rated our service as “Excellent” on TrustPilot. Explore or range today or speak with our sales team for further information and advice.