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Combi Boiler or System Boiler?

Posted On Wednesday, 05 January 2022 20:15
Combi Boiler or System Boiler?

Purchasing a boiler is a significant investment, so it's one that you'll want to get right. In the past, the boiler was simply a machine that provided heat for your home, but now they offer much more functionality, and with so many options it's essential to make the right choice.

Most people end up having to make a choice between a combination boiler and a system boiler. But which is the right one for you? While cheap radiators can provide an excellent saving when your budget is tight, getting the wrong boiler might end up costing you a lot more in the long term!

The Combination Boiler

Combi boilers get their name because they are both high-efficiency water heaters while also being central heating boilers. With two heat exchangers, the combi boiler works by having one linked to the hot water supply and one connected to the radiators of the central heating system.  

When you need hot water, a sensor tells the combi boiler to burn fuel to make the exchanger hot. As the water flows over the exchanger, it heats up, ready for use. There is no storage of hot water with a combi boiler; it heats up the supply on demand when you turn the tap on.

Pros of a Combination Boiler

  1. 1. Combination boilers are incredibly efficient, with many achieving levels in excess of 96%. That means if the energy used to produce your hot water, only 4% is lost during the healing process. That then means lower energy bills and reduced carbon emissions. 
  1. 2. As the combi boiler doesn't need a water tank or cylinder, combi boilers are easy to install into homes where space is at a premium. Many combi boilers fit into a cupboard-sized space making it easy to install into the kitchen area.
  1. 3. Combi boilers provide hot water on demand. As soon as you turn on the hot water tap, the boiler fires into action and delivers hot water. System and regular boilers heat the water in advance and then store it within the hot water cylinder. While that may seem like a good idea, when you've used up the tank, then you have to wait for another tank full to heat up.
  1. 4. Combi boilers offer a real opportunity to reduce your heating bills, and that's because water is only heated in small quantities as you need it. Meanwhile, a system boiler heats a hot water cylinder full, and that will begin to lose some of its heat over time. 

Cons of a Combination Boiler

  1. 1. Because they don't have a hot water tank, there are times when they don't work as efficiently, and you may find yourself having a cold shower if someone turns on the tap in the kitchen!
  1. 2. Unlike system boilers, the combi doesn't have a backup immersion heater. So, if the boiler breaks down, you're going to be left without any hot water or heating. 
  1. 3. Older heating systems are designed for low levels of water pressure. With the combi boiler using water directly from the mains, it means that the pressure is much higher. This can then result in leaks and cracks in older pipework. 

The System Boiler

The system boiler takes its water supply directly from the water mains. So that means that there is no need for a cold-water tank. 

The cold water enters the boiler first and then passes by the heat exchanger to warm it to the required temperature. The hot water is then transferred into the hot water cylinder, and it then stays there until it's required. Because a larger amount of hot water is available, multiple taps or showers can be used at once. 

Pros of a System Boiler

  1. 1. Combi boilers usually struggle to provide the water pressure needed for a power shower. However, with a system boiler and a pump, then you can feel the full benefit
  1. 2. Hot water can be delivered much more quickly compared to a combi boiler. So there's no waiting for the hot water to be delivered. As soon as you turn on the tap, you'll have your hot water supplied
  1. 3. Unlike a regular boiler, there's no need for a cold water storage tank. So, system boilers take up much less space when compared to a regular boiler. 
  1. 4. System boilers can be set up so that their energy supply comes from solar energy. This can then deliver environmental benefits as well as reduced energy bills.

Cons of a System Boiler

  1. 1. The system boiler needs a hot water cylinder, which means more space than combi boilers. In many homes, the cylinder is fitted into the airing cupboard, but with storage being at a premium in most homes, you might not want to give up this space
  1. 2. Your hot water is limited by the size of the hot water cylinder. So, if the whole family wants a shower, then the last person might find there's no hot water left!  
  1. 3. Once the preheated hot water has been used, then you'll have to wait until the tank heats more water.
  1. 4. When you store hot water, there is going to be some heat loss, even with the benefit of insulation. This, in turn, affects the boiler's level of energy efficiency. 
  1. 5. System boilers heat the hot water in advance of when you need it. If your life is very predictable, that might be okay. But if the times you need hot water vary hugely, then that might be difficult to plan for. 

Which is the best boiler?

Well, there's no one correct answer to that one. Both the combi boiler and the system boiler can be the right choice depending on the size of your home and your hot water needs. So, before making a purchase, ensure that you carefully consider what you need from your boiler to help [ you make the right choice.

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