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Understanding your boiler

Heating and hot water account for more than half of a typical household’s annual energy bills. We’ve got some facts and tips to help you keep costs to a minimum and get the best out of your boiler:

Combi or regular?

Combi (combination) boilers heat water on demand and do not require a separate hot water tank. Regular boilers store hot water until it is required. The cylinder or tank is heated at set times using a programmer.

Which is better?

Regular boilers are more efficient when it comes to heating hot water in the first place, but while the water is being stored in the tank some of that heat is lost. This means that combi boilers may be more efficient overall.

The best kind of boiler is an efficient one!

Replacing an old G-rated boiler with an A-rated system with a full set of heating controls could save you around £415 a year*. Even just installing and using a full set of heating controls can save around £140 a year.

*Assumes that you already have a programme and room thermostat                                                                                                                                           

Top tips

Heating little things that make a difference:


Fit radiator controls and use them to control heat in every room in the house – for example, keep heat on a low setting in rooms that aren’t used much.


Use your timer to manage when you need heat – for example don’t set heating to be on while you’re out of the house or through the night while you’re in bed.


Use a room thermostat and keep the temperature at a comfortable level; we suggest between 18-21 degrees.


If you have a hot water tank, keep the temperature set to a minimum of 60 degrees. For combi boilers, you can set the water temperature to a lower setting to save energy.


Are your radiators working efficiently? ‘Bleeding’ them can remove trapped air and keep them in good working order.


Make sure you get your boiler serviced regularly to ensure it’s safe and working at maximum efficiency.

Do you have electric storage heaters?

If so, upgrading them to modern slim line heaters or high heat retention storage heaters could save between £330 and £970 a year on electricity bills.

Download our Understanding your boiler PDF.

Savings based on a typical three-bedroom semi-detached gas heated house, with an 88% efficient gas boiler and average gas tariff of 8p/kWh and electricity tariff of 30p/kWh. Correct as of July 2023.

Last updated: 6 September 2023