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Switching heating off when it's not needed

Within our test schedule we’ve tackled an age-old question; is it better to turn your heating off when it's not needed rather than to leave it running at a lower temperature?

The answer to the question turned out to be yes – it is cheaper to switch the heating on and off; but not by much.

The idea behind leaving the system on all day is that it takes more energy to heat the structure of the building up again after it’s cooled down. A boiler will certainly burn more gas to heat a building from cold, but this seems to be not so much that longer running times are better.

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We ran two tests as a comparison, using a programmable room thermostat. In test 1, the heating system was set to maintain 21 degrees C in the living room with the following time profile:


-    On at 06:30
-    Off at 09:00
-    On at 15:30
-    Off at 23:00

 

In test 2, The programmable room thermostat was set to maintain 21 degrees C in the living room during ‘on’ periods and a setback temperature of 16 degrees C during other periods. The heating system was therefore set to operate on the following time profile:


-    16C at 00:00
-    21C at 06:30
-    16C at 09:00
-    21C at 15:30
-    16C at 23:00

Running the heating system for 24 hours with the test 1 profile used 68.3 kWh of gas, while test 2 used 70.2 kWh, showing that maintaining a setback temperature used 2.7% more energy. This is only a small increase but would still cost about £33 per year so you may see this as a saving worth making. However, if there are vulnerable people in the home then the benefits of maintaining a setback temperature overnight may be worthwhile.


As with all these tests you do need to consider that they relate to a specific set of circumstances and should only be seen as a general rule of how to use your heating system.

 

In case you were wondering, we also looked at data to see what might happen if you left your heating system permanently on to maintain 21 degrees C for 24 hours – this indicated gas usage of around 70% more than the type of profile in test 1, so it’s definitely not cheaper to just leave your heating on all the time!

Other ways of reducing energy use:
Adjusting time and temperature settings
Lowering temperatures around your home
Running your heating for longer, rather than short bursts


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