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How heating and hot water controls can reduce fuel bills

The right controls will let you set your heating and hot water to come on and switch off when you need them, heat the areas of your home you want, and decide how warm you want each area to be. Whatever the age of your boiler, fitting a boiler thermostat, a timer or programmer, a room thermostat and thermostatic radiator valves (TRVs) can help you save money on your fuel bills.  Correct boiler controls can also help to ensure that your system meets the requirements of Part L of the Building Regulations.

Water storage cylinder

If you have a heat only or system boiler, your hot water is stored in a cylinder.  Once the water has reached the temperature you have set, a cylinder thermostat will turn off the heat supply from the boiler.  You should set the cylinder thermostat at between 60ºC and 65ºC, which is hot enough to kill off harmful bacteria in the water, but is also hot enough to scald. For extra safety, consider installing a thermostatic mixing valve which will automatically ensure that the hot water you draw off at the tap is at a safe temperature.

If your hot water cylinder or tank is well enough insulated, you may find that the morning's hot water stays hot enough to use in the evenings.

What you can save:
• A hot water cylinder thermostat can save £30 and 130kg carbon dioxide a year.
• Fit a hot water tank insulation jacket: £45 and 170kg carbon dioxide a year
(Source: Energy Saving Trust)

Room thermostats

A room thermostat will stop your home getting warmer than it needs to be: it will turn the heating on until the room reaches the temperature you have set, and then switch it off until the temperature drops.
Typically your room thermostat should be set around 18°C and 21°C. Try turning your thermostat down a degree or two and seeing if you are still warm enough - you could save even more on your fuel bills. You don't need to turn your thermostat up when it is colder outside: the house will heat up to the set temperature whatever the weather. It may take a little longer on colder days, so you might want to set your heating to come on earlier in the winter.

What you can save:
• Install a room thermostat and save £70 and 280kg carbon dioxide a year (source: Energy Saving Trust)

Programmer or time control

Programmers allow you to set 'on' and 'off' time periods. Most models will let you set the central heating and domestic hot water to go on and off at different times.
If you insulate your home, it will warm up more quickly and cool down more slowly, so you'll save money on heating.


Heating the whole house at once is like controlling all your lights from one switch. Zoning lets you heat specific areas when you use them, which can save you money on your fuel bills.

Zoning allows you to divide your home into separate areas, so you can heat areas depending on when and where you spend time in your home. For example, you could heat your living rooms during the day and only heat the bedrooms in the evening, so you are not using fuel to heat the rooms you don't use so often.

Thermostatic radiator valves (TRVs)

Thermostatic radiator valves reduce the flow of water through the radiator they are fitted to when the temperature goes above a certain setting. Set them to the level you want for the room: a lower setting uses less energy and so will save you money.

Boiler interlock

This is not a control but a system of wiring that turns the boiler off when neither the room thermostat nor the cylinder thermostat needs it. Without this the boiler can continue to 'cycle', wasting energy.

Boiler thermostat

Your boiler thermostat sets the temperature of the water that will be pumped from the boiler through the radiators to heat your home. The higher this is set, the quicker the system will heat your home. If it is not set high enough, when it is very cold outside your home may not reach your desired temperature.If you have a room thermostat and a boiler interlock, you can set the boiler thermostat quite high and the room controls will regulate the room temperature for you.
Your boiler control thermostat should always be set to a higher temperature than the cylinder thermostat, if you have one.

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