Boilers: Boiler energy efficiency
The cost of heating your home, particularly during the colder winter months, makes up a large proportion of household running costs.
You can keep heating costs down by making smart heating choices – from choosing the most energy and cost-efficient heating appliances, right down to draught proofing your letterbox – to keep your home cosy.
Lower heating costs: heating products
Gas prices are rising, so efficiency is crucial
The age and type of boiler you have affects how efficient it is. A modern condensing boiler is the most efficient boiler on the market – find out more in our condensing boilers explained page.
According to the Energy Saving Trust, if everyone in the UK with gas or oil central heating installed a high efficiency condensing boiler with full sets of heating controls, we would save enough energy to heat nearly 1.9 million homes for a whole year and save around 6.7 million tonnes of CO2.
The efficiency of a boiler is normally expressed as a percentage. Since October 2010 only boilers that are 88% or more efficient can be installed in homes and most of the boilers you can buy now are between 88% and 89.7% efficient.
It's worth noting that you wouldn't expect to see a difference in your gas bills if you choose one that was 98.7% efficient over an 88% efficient one. The big saving comes from making a leap from an old inefficient boiler to a new one.
How much could you save?
Based on a saving of 25% gas usage, the Energy Saving Trust estimates the average saving per household to be £225, but this would depend on you spending £900 per year on your gas bill right now.
The table below illustrates just how much a modern condensing boiler could cut your gas bills by, depending on the size of your house (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.)
However, these figures are based on a gas unit price of just 1.63 pence per kW, in 2010 the average price of gas was twice that value, so your savings could be higher.
| 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 |
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.
Using heating controls effectively
Cut heating costs by turning your thermostat down
Heating controls let you take charge of when, where and at which temperature your heating is operating. It’s a good way of managing your heating costs, as you can ensure that your heating is only on in the rooms and at the times you want it to be. There are four main types:
- timer – turns your boiler on or off at set times.
- room thermostat – measures how warm your room is and adjusts the boiler operation accordingly. Wireless thermostats are now available, which makes the location of your thermostat more flexible.
- programmer – a more sophisticated version of a timer, you can set different heating patterns for different days of the week and sometimes alter the pattern - for a party or holiday for instance.
- thermostatic radiator valves – these 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.
Heating controls also allow you to a room temperature of your choice. A temperature of 18°C for your bedroom and 21°C for your living room should suffice, unless you have a small baby or an elderly or sick person in your home.
Set the temperature on your hot water cylinder to 60ºC to avoid overheating your hot water supply.
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.
Positioning your thermostat
Installing a programmable room thermostat in your home allows you to easily and accurately manage the temperature of your home.
Programmable thermostats, room thermostats and thermostatic radiator valves all need a free flow of air to sense the temperature accurately. They must not be covered by curtains or blocked by furniture. Nearby electric fires, televisions or lamps could also stop them from working properly.
Turning down the thermostat on your heating could slash up to 10% off your heating costs.
Radiator efficiency
Keep your radiators clear
‘Radiators’ actually work by convection – cold air enters at the bottom, is drawn through the radiator and hot air leaves through the top. You can reduce your heating costs by ensuring each radiator in your home is able to properly circulate heat.
Blocking convection reduces the effectiveness of your heating, so take the following free steps to make them more effective:
- pull furniture away from radiators
- don't use radiator cabinets to disguise
- don't cover your radiators with curtains.
Lower heating costs: improve your habits
Keep warm with an extra layer of clothing
Of course, wasting energy unnecessarily on heating can be down to our bad habits as much as inefficient products or lack of home insulation. Small changes to your daily routine can keep you and your property warm without turning up the thermostat. You'll reduce your heating costs and cut your home's carbon footprint.
- curtains – use the natural light and warmth of the sun to keep your home warm during the day – then close your curtains in the evening to keep that free heat inside, and to protect your room from draughty windows.
- ventilation – letting air into your home will keep your house fresh, but try to open windows to air rooms when the sun is on them, then keep windows and doors closed when the heating is on.
- room by room – turn the radiator down or even off in rooms that aren’t used regularly, but check for signs of damp or condensation regularly.
- add a layer – make a warm jumper, not your central heating, your first resort when the mercury plunges.
Lower heating costs: low cost changes
Draught proof and save £10-£15 a year
Finally, reduce your heating bills with some simple and cheap energy saving measures:
Draught-proof doors
Invest in some low-cost measures to insulate doors around your home and reduce heating costs.
- Add a self-adhesive foam or rubber seal around the door cavity
- Add a threshold strip to the bottom of the door with a brush to cover any gaps
- Draught-proof your letterbox with a seal around or under the flap, and a brush inside
- Protect keyholes with a cover
Heat-reflective foil
Fit this behind radiators on outside walls with the shiny side facing into the room. This reflects heat from the surface of the radiator into the room and away from the wall.
Seal draughty gaps
Fill any gaps between skirting boards and the floor. This can be done with wood moulding or flexible silicon sealant.
Loft hatch insulation
Insulate the loft hatch with a strip of foam or rubber seal.
More on boilers and cutting heating costs...
- Cut your bills with our energy saving tips
- Read our guide to loft insulation
- Find the best boiler for your home with our reviews
