Modern boilers are more efficient for several reasons, but their main advantage is that they are all condensing boilers. All well-maintained boilers burn their fuel very efficiently, but they inevitably lose some heat in the hot gases that escape up the flue. A condensing boiler has a larger heat exchanger, so it recovers more heat, sends cooler gases up the flue and is more efficient.
Sometimes the flue gases get so cool that the water vapour in the gas condenses out, hence the name, and even more energy is recovered from the condensing vapour.
If it is time to change your boiler, you need to decide what type of boiler is right for you. Here are some things to consider:
If you have mains gas, a gas boiler is likely to be the cheapest heating option. Our average fuel prices as of April 2018 show gas to be the cheapest heating fuel per kWh, compared to oil, economy 7, LPG and house coal.
Alternatively you may want to get a gas connection to your home. The company that owns and operates the gas network in your area may be able to help with the cost of getting a new connection, and it may even be fully funded. Contact Energy Networks Association for further information.
Most old gas and oil boilers are regular boilers that have a separate hot water cylinder to store hot water, rather than providing it directly from the boiler. When you replace your boiler you can buy a new regular boiler, and keep your hot water cylinder, or buy a combi boiler that doesn't need a cylinder.
A regular boiler is more efficient than a combi at producing hot water in the first place, but then some heat is lost from the hot water cylinder, so a combi may be more efficient overall. Which is better for you will depend on different things:
Large families using lots of hot water are likely to be better off with a regular boiler, whereas smaller households using less may be better off with a combi boiler.
Combi boilers don’t need hot water cylinders, and therefore require less space in your home.
If you’re thinking of installing solar water heating, it’s worth noting that many combi boilers are not compatible with this heating system or cannot use it so effectively.
There is a wide range of heating controls available that will help your heating system work more efficiently and help keep your bills down. Have a look at our Thermostats and Controls page to see what might be appropriate for your system.
Some of the heat generated by your boiler escapes through the flue. Passive flue gas heat recovery systems capture some of this lost energy and use it to heat your water, making your heating system more efficient and saving you money. They are only available for combi boilers as they provide heat to the cold water supply that is feeding the hot water output.
Some models include some heat storage, which increase the savings but usually also increases the installation cost.
Some new boilers are made with flue gas heat recovery already incorporated, so there is no need to buy a separate heat recovery device.
New hot water cylinders are factory insulated to help keep your hot water at the right temperature for longer. They play an important role in supplying you with readily available hot water, so it’s important that they are fully insulated to prevent heat escaping.
If you have an old cylinder you could save around £20 a year by topping up the insulation to 80mm. Alternatively if you are replacing your cylinder, you can save energy by making sure that the cylinder is no bigger than you need it.
Corrosion deposits in an older central heating system can cause a substantial reduction in the effectiveness of the radiators, and the system as a whole. The build-up of scale in heating circuits and on boiler components can cause a reduction in efficiency too.
Using an effective chemical inhibitor can decrease the corrosion rate and prevent the build-up of sludge and scale, thus preventing deterioration and helping to maintain efficiency.
* Information taken from Energy Saving Trust