There are three main types of gas boilers, these are:

Condensing boilers

These are the most efficient sort, typically converting 88 per cent of fuel into heat compared with the 76 per cent that standard boilers can manage. That means you could save at least 12 per cent on your fuel bills, or even more if you have an older boiler.

Combination (combi) boilers

These are popular in flats and small houses where space is limited. As their name suggests, combi boilers do two jobs in one, acting as a central heating boiler and a hot water cylinder. Because they are compact they can be wall-mounted in the kitchen. This kind of boiler can be more economical as you only heat the water you use. However, there is a short delay between turning on the tap and the water running hot. Since there's no separate hot water cylinder, you'll have a bit more space in your home as you won't need an airing cupboard.

Non-condensing boilers

If a condensing boiler isn't right for you, the next best thing is a modern fan-assisted boiler. Compared with old-fashioned boilers, these models are lighter, warm up and cool down more quickly and therefore waste less heat. All of which can add up to a saving of 20p in the pound compared with boilers over 15 years old.

From the 1 April 2005 all gas boilers installed or replaced must be condensing boilers rated SEDBUK A or B (an efficiency of 86 per cent or more).

A controlled gas central heating system will typically have:

  • A time programmer and room thermostat, or a combined programmable room thermostat instead of separate programmer and room thermostat.
  • A cylinder thermostat
  • Thermostatic radiator valves (TRVs)

What is a programmer/timer?

A programmer or timer allows you to set times for your heating and hot water to come on and go off to suit your lifestyle. Once set, the programmer automatically controls the times at which your central heating system switches on and off. There are generally two types of programmer/timer, a manual clock with tabs to set the timing periods and electronic ones. Make sure that the programmer / timer is set to the correct time of day. If you have a combination (combi) boiler then you will only set the heating periods for the radiators as hot water is heated instantly when the hot water taps are opened.

It is best to set your heating to come on about half an hour before you want your home warm, and to go off about half an hour before you go out or go to bed. Ideally you should run the system in two periods and for no more than nine hours per day in total.

What is a room thermostat?

A room thermostat constantly measures and controls the air temperature of your home's main living spaces and can be set to whatever temperature suits you best. They are usually mounted on a wall in the hallway, living room, stairs or landing areas and will have a dial with a range of temperatures on it. You can set this dial to the temperature you want your home to be.

Depending on you and your situation, a room thermostat should be set as follows:

  • If you're a pensioner or infirm then your room thermostat should be set at 21°-23°C (70°-73°F)
  • Otherwise 18°-21°C (66°-70°F) is fine for healthy adults.

When the temperature falls below the setting, the thermostat switches on the central heating; once the air reaches the set temperature, the thermostat switches the heating off.

Please note that the timer or programmer needs to be switched on for the thermostat to work.

What is a programmable room thermostat?

A programmable room thermostat lets you choose the times you want your home to be heated and the temperature you want it to reach while it is on. In other words, it allows you to heat rooms or the whole house to different temperatures in your home at appropriate times of the day and week.

What are thermostatic radiator valves (TRVs)?

TRVs sense the air temperature around them and regulate the flow of hot water entering the radiators to keep a set temperature in a room. Again, they can help you save money and energy - by allowing temperatures in some rooms than in others, and to turn off the heating in rooms that aren't used.

In the majority of cases TRVs can not turn off the boiler when the whole house has reached the right temperature. To do that, you will need a room thermostat as well. Radiators in the space containing the room thermostat should not normally have TRVs. But if they do, you should keep the TRVs on their highest possible settings, and set the room thermostat to the required temperature instead. By installing TRVs, you could save around £10 a year and around 45kg of CO2 a year.

If your boiler is not working

Carry out the following simple checks.

  • Room thermostat (if fitted)- If this is turned down or the property is sufficiently warm the heating may not come on.
  • Thermostatic Radiator Valves (if fitted) - If all the valves have been turned to the * symbol they will not allow the radiators to become hot (except the radiator without one which should be hot).
  • Timer/programmer - Has this been set correctly? Time of day (24hr clock), the on off times of the radiators, and the hot water heating if a non combination boiler (combi).
  • Has there been a power cut? - When the power is off most Central Heating boilers will not work. If the electricity supply is off or has been off for a lengthy period of time the timer/ programmer clock may need to be reset using the 24hr clock.
  • Has the fused spur which is located by the boiler been switched off? If it has then the boiler will not work.
  • Do you have enough credit in the gas and/or electricity meter? If you have run out of credit and have used the emergency credit in either meter then your heating will not work. Has the gas supply been cut off?

Installing a condensing boiler along with a full set of heating controls could save as much as 40 per cent of your heating fuel bill: around £275 a year.