Domestic gas boilers

We often get asked the difference between the most common boiler types, although we take it for granted as we work in this industry there is still confusion so hopefully this will help a little.

Condensing boiler

- All gas boilers sold in the U.K are condensing boilers*, this simply means they are capable of condensing which is explained further in another post.  A common misconception is "condensing" and "combination" being the same thing.

*Note - There are some exceptions to the rule on condensing boilers but for clarity I haven't gone into it.

Open vent or heat only

- These are "traditional"  boilers which simply make heat.  The system will still need an external pump, motorised valves, a water store and some way of pressure accommodation, either a loft tank or an expansion vessel. 

These are still popular due to cost and ease of install although don't necessarily give the optimum upgrade.

System boiler  

-  A system boiler incorporates a pump and pressure vessel, it is also configured for and has the ability to be attached to an external hot water store.

These are great for integration and more intelligent control of heating and hot water.

Combination boiler

- Probably the most commonly known boiler type, especially in cities.  A combination boiler combines heating and hot water production within one box, it doesn't need tanks or a cylinder for hot water.

These are great for smaller properties, they are not so great for high demand hot water.  They aren't as efficient and don't cope with high flow rates.

Storage combination boiler  

- A bit of a niche product, a storage combination has a small internal tank and the boiler feeds it to provide hot water.  Not as efficient as a separate cylinder generally but better for running costs and flow rates than a standard combination boiler.

These are great for a medium sized property with multiple showers but restricted space for the hot water store.

Hybrid gas boiler and heat pump

As the name suggests they have a gas boiler but integrate an air source heat pump.

These are great for more clean homes as they don't rely on fossil fuels as much and were part government grants (which hopefully will come back one day).  Of course if you have solar pv and can use the generated power to run the heat pump then this would be a massive benefit.