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  • Quick and easy
  • Wide choice of installers
  • Cheaper than many other heating systems

What it is

"Condensing boiler" is just a name for a modern, efficient boiler that turns more of the heat it produces into hot water for your radiators and taps. 

When a boiler burns gas, it converts most of that heat into hot water which is then used to heat your radiators, and to provide hot water for your taps. The rest of the heat disappears up the flue as hot gases, and is wasted. 
A modern efficient boiler uses a bigger heat exchanger to convert more of the heat to hot water, so less heat is wasted in the flue gases. This makes it more efficient, so you burn less gas to heat your home, and you save money. 
Sometimes the flue gases are cooled so much that water vapour condenses, producing a visible white plume. This is why modern boilers are called condensing boilers. 

Is it right for me? 

If you have a gas boiler that was fitted before 2005, then the chances are that it is an inefficient boiler. If this is the case, then you could cut your heating bills significantly by replacing it with a modern efficient model. 

There are a few things you can do to check if your existing boiler is a condensing model: 

  • If there is a pipe running from the boiler to an outside drain, then it's a condensing model – if not, it isn’t.
  • If the flue is made of plastic, then it’s condensing – if not, it probably isn’t.
  • If you can see clouds of white “steam” coming out of the flue in cold weather, then it’s a condensing model – if it’s not condensing, you’ll hardly ever see this.

If you’re going to replace your boiler, but you want to go for something greener than gas, then you could consider one of these: 

  • air source heat pump
  • ground source heat pump
  • wood boiler 
  • micro CHP 

Different types of condensing boiler

There are two main types of gas boiler – those with a hot water cylinder and those without. 

Combi boilers provide hot water on demand. Whenever you turn a hot tap on, the boiler fires up, and starts heating the water supply to the tap. There is no hot water cylinder. 
Regular boilers provide hot water by heating a separate hot water cylinder. When you turn on a hot tap, the hot water comes directly from the cylinder. 
There is a third type, known as a system boiler. This has some of the elements of a combi boiler, making it easier to install, but it provides hot water via a cylinder, just like a regular boiler. 

Living with your new boiler 

Your new boiler should work just like your old one, only better, but there are things you can do to make the most of the benefits. 

Your new condensing boiler should operate much like your old one, so you shouldn’t notice any difference other than lower gas bills. However, the new boiler may give out more heat, or operate at a different temperature. You should check that you’re using your heating controls effectively, otherwise you might not get the maximum benefit from your new boiler. 
Your installer may fit new heating controls when they fit the boiler, particularly if your old controls don’t meet the current standards. Make sure your installer explains what the new controls are and how you should use them.