Buying a better gas boiler

Heating and hot water accounts for well over half of the total energy use in the home, so if you have an old gas boiler, changing to a more efficient model will save you money and give you a higher score on your EPC.

Boiler efficiency

Boiler efficiency is defined as a percentage, with gas boiler installation now restricted by regulations to those with a score of 88% or better. The energy efficiency is rated from A to G, with modern condensing boilers getting an ‘A’ rating.

Boilers more than 15 years old are likely to be inefficient due to hot gases escaping up the flue. Modern condensing boilers have larger heat exchangers that recover more heat.

If your boiler has a plastic flue and a second pipe coming out of the bottom to drain condensate outdoors it is a condensing type. If it does not have one of these, it is worth considering an upgrade.

What is available?

If you have a mains gas supply, a gas boiler is likely to be the cheapest option. There are two main types.  Regular (or conventional) boiler systems heat the water and store it in a cylinder.  Combination (combi) boilers heat the water on demand without the need for a cylinder. A third type, system boilers, are typically used in large houses with a substantial hot water demand.

Regular boiler systems take up quite a lot of space, but provide the highest hot water flow rate. However, they do lose some heat from hot water stored in the cylinder. They are generally a good choice for homes with more than one bathroom and a predictable hot water demand.

Combination boilers are the most popular choice as they are cheaper to install, more compact, and they cannot run out of hot water. They are less efficient than regular boilers when heating small quantities. They are suited to homes with limited space and no existing hot water tank, and those with a less predictable hot water demand. 

A new boiler is a big investment, and the technology can be complex, so check with a qualified installer what would be best for your home.

What if I don’t have gas?

Gas boilers are available that run on liquefied petroleum gas (LPG) from a tank, if there is outdoor space for one.  Oil-fired heating is a popular alternative, though heating oil prices can be volatile. With Government support schemes, low-carbon alternatives such as heat pumps or biomass boilers may present a cheaper option.

How much can I save?

A smaller, cheaper gas boiler may suffice in a well insulated home, so make sure you do that first.  New boiler prices range from approximately £500 to £2,500. Installation costs vary, so getting at least three quotes is recommended.

Your annual savings will depend on how inefficient your old boiler was. As an example, replacing a G-rated gas boiler with an A-rated condensing boiler could save up to £325 in a detached house, or £200 in an average semi-detached house.  An £1,800 gas boiler bought to replace a 60% efficiency boiler will pay for itself in seven and a half years.

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