Boilers: Boiler maintenance tips Boiler efficiency
If you have gas central heating, your boiler will account for around 60% of your home's CO2 emissions, according to the Energy Saving Trust. This makes boiler efficiency a key priority if you're looking to cut your carbon footprint and your energy bills.
An efficient boiler will cut your heating costs
How Which? tests boiler efficiency
Boiler efficiency is a key part of our independent boiler tests, which meet European standards. We check each boiler to see how much of the gas it burns is converted into heat. This measures the boiler's efficiency.
Our Best Buy boilers all perform well for energy efficiency, and should help to cut your heating costs.
Sedbuk: how boilers are rated for efficiency
Sedbuk, which stands for Seasonal Efficiency of Domestic Boilers in the UK, is a system used to classify and compare boilers on how efficient they are at converting fuel into heat. Traditionally, Sedbuk ratings were shown on labels as a letter A-G, but these letter labels have been withdrawn to avoid confusion with the European energy labels, which use similar ratings but are based on different principles. As a result, there are currently two different types of Sebuk ratings you may see on labels, reflecting the old and new types of Sedbuk ratings.
- Sedbuk 2005 - this older system of Sebuk ratings rates boiler efficiency from A to G rating, with A-rated boilers being more than 90% efficient.
- Sedbuk 2009 - this newer system of ratings shows boiler efficiency as a percentage, rather than A-G.
All new boilers should be rated using Sedbuk 2009, but you may still see older models which were tested under the old Sebuk 2005 system. You can check how the different types of ratings relate to each other using our chart on our Boiler FAQs page.
Under the new Sedbuk 2009 system a Sedbuk 2005 90% efficient A-rated gas, oil or LGP boilers boiler works out as 88% efficient. The 2% difference between Sedbuk 2005 and 2009 is mainly down to differences in efficiencies between using a boiler for space heating in the winter months and only using it for water heating in the summer.
How boiler efficiency differs between models
The age and type of boiler you have will affect how efficient it is. The efficiency of a boiler is normally expressed as a percentage.
The table below illustrates how a modern condensing model could cut the cost of heating your home, whatever size house you've got.
(A boiler that's 15 years old or more is classed as 'old' in these calculations. A lightweight boiler can be attached to a wall; a heavyweight boiler is floor standing.)
| Annual fuel costs with different boiler types (source: Sedbuk) | ||||||
|---|---|---|---|---|---|---|
| Boiler type | Efficiency | Flat | Bungalow | Terraced | Semi-detached | Detached |
| Old gas heavy weight | 55% | £308 | £393 | £408 | £458 | £634 |
| Old gas light weight | 65% | £266 | £338 | £350 | £393 | £542 |
| New non-condensing | 78% | £227 | £287 | £298 | £333 | £457 |
| New condensing | 88% | £205 | £258 | £268 | £299 | £409 |
Condensing boilers
A high efficiency condensing boiler is a good choice if you're looking for a greener and more efficient boiler. Condensing boilers make better use of the heat they generate from burning fuels such as gas or oil.
With a conventional boiler, some heat is wasted in the form of hot gases released from the flue. A condensing boiler captures some of the heat from these gases and uses it to heat water returning from your central heating system. It therefore requires less heat from the burner and is more efficient.
You can find more information on condensing boilers in our boiler review.
Cut heating costs by turning your thermostat down
Improving heating and boiler efficiency
Being more efficient with your boiler doesn't just stop at the type of boiler you choose - there are also easy ways to cut your heating bills and optimise boiler efficiency.
Use a programmer
Heating programmers save you the hassle of having to manually switch the heating on and off and will help you to minimise unnecessary use. You can predetermine the times your heating is on in advance, set different programmes for different days of the week and set your heating system before you go away.
Room thermostats
Installing a programmable room thermostat in your home allows you to easily and accurately manage the temperature of your home. Wireless thermostats are now available, which makes the location of your thermostat more flexible. Position your thermostat away from electric fires, televisions or lamps, which could stop it from working properly.
Thermostatic radiator valves
Managing your radiators will help your central heating system to heat your home more efficiently and only in the areas of your home that require warmth. Thermostatic valves allow you to easily adjust the temperature of individual radiators and turn radiators off or on according to whether you're using a room or not.
Turn it down
Turning your central heating down by a degree can cut your heating bills by up to 10%.
Our guide to cutting your energy costs has more practical energy efficiency tips for you to adopt at home.
More on boilers and saving money...
- Check our boiler servicing contract reviews
- 10 tips to help cut your heating bill
- Find the best boiler with our boiler reviews
