What is boiler efficiency?
A boiler’s energy efficiency is the percentage of useful heat you get from it in relation to the amount of fuel gas that was put in. For example, a boiler is said to be 90% efficient if its heat loss is 10% of the fuel that was input. A boiler can never be 100% efficient as there is always some heat escaping through the flue along with the products of combustion.
How to find out your boiler’s energy efficiency
Look for the energy efficiency label on the boiler
New boilers will have this label either attached to the boiler casing or enclosed with the User Manual.
Age of the boiler
This is usually a good indicator of how efficient your boiler is likely to be. Like most appliances, the older the boiler, the less efficient components become.
Type of boiler
Do you have a condensing boiler? Condensing boilers recover more energy from the water vapour produced and use this to heat more water. Boilers fitted after 2005 will be condensing. Before this date, non condensing boilers are likely to be a lot less efficient.
Search the boiler database
If you have an older boiler and cannot find the efficiency label, you should be able to search on the Building Energy Performance products database. You will need to know the make, model and heat output in kW of your boiler. Search the database here
How is boiler efficiency measured?
Boiler ratings are a measure of thermal efficiency which is the rate at which the heat exchanger converts the energy into usable heat. Energy Output/Energy Input X 100. The letter ratings from A to G that you see on appliances are based on this percentage. The higher the percentage, the more efficient it is and is given a high rating.
The ErP, or Energy-related Products label is used for modern appliances including boilers and gives consumers an easy and user-friendly comparison of energy efficiency levels so they can make informed choices when purchasing. The labelling starts at A++ which is the most efficient, down to G – the least efficient. At 90%-93%, modern condensing boilers are A-rated.
The higher the rating on the energy scale, the more efficient the appliance is and the less energy it will consume. It is also an indication of how much that appliance will cost to run. Older boilers are less likely to be energy efficient.
What is the most efficient type of boiler?
A combi boiler heats water directly from the mains when you turn on the tap. They are both cost effective and energy efficient as the water is heated instantly rather than being heated and then stored in a cylinder.
A system boiler requires a cylinder for storing hot water and there will be some heat loss. But if they are installed alongside solar thermal systems, they can be a very energy efficient option.
A regular boiler heats up the water in a more efficient way than a combi but as the hot water is stored, there is a heat loss here which makes it less efficient.
Keeping an old inefficient boiler running costs more in annual energy bills than buying a new A rated boiler. Sometimes it’s sensible to buy a replacement boiler sooner rather than later. You can see how much a new boiler will cost by clicking on the banner below.
*The information in this article should be used for general guidance only and not as financial or health advice. Full details are on the link in the footer to our disclaimer page. Always discuss your requirements with a competent and suitably qualified professional before undertaking any work.
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