The Difference Between a Combi and System Boiler

One question our plumbers often get asked is ‘what’s the difference between a combi and a system boiler’. This guide will tell you the difference between the two…

Let’s start with a system boiler, most system boilers take the cold water from the mains supply and then heat it with a heat exchanger, which transfers energy from the gas to the water. Once the water is hot it will then be moved to a storage cylinder where it is kept hot until you need it. The heating system is within the system, hence the name.

On the other hand, a combi boiler is a more efficient single unit that provides hot water for the water supply and for the heating. A combi boiler will take water from the mains and it will heat it on demand, whenever a tap is turned on. Because it heats water on demand, you won’t need a hot water cylinder if you go for a combi boiler. The combi boiler gets its name from the combination of 2 tasks it does, heating and water, all within one boiler. 

Which is Better?

Another question our plumbers get asked is which is better. There isn’t an easy answer to this as it will depend on your home. The huge system boiler with its hot water tank can be the best option for large homes where hot water is in high demand. If you have a system boiler you can run a hot bath in only a few minutes, as the water is already hot in the tank, you don’t need to wait for it to warm up. However, with system boilers you do run the risk of running out of hot water, if you use all the stored water you will have to wait for it to heat up again.

If you have a smaller home, the combi boiler is probably best for you. Combi boilers come with improved efficiency, with many having a 92% efficiency rate. Combi boilers are also easier to install, and they require less room as you don’t need space for a water cylinder. However, if you have multiple bathrooms a combi boiler may struggle to cope with the demand for hot water in more than one place at once.  

As you can see, even as experienced plumbers, it is not easy to say which type of boiler is the best. If you have read this article and you are still wondering, why not give one of our plumbers a call to chat about them further?