How to Set Your Heating Thermostat Correctly: Temperatures and Savings

The heating thermostat is one of the simplest levers for reducing your energy bill, but it is often badly set: too hot in the occupied rooms, not lowered enough at night, or installed somewhere that skews the reading. Yet a few well-thought-out settings are enough to combine comfort and frugality. Here are the reference temperatures, the good practices and the pitfalls to avoid to get the best from your thermostat, whether it is wired, smart or simply mechanical.

The recommended temperatures room by room

• Living rooms (lounge, sitting room): 19 °C, the reference temperature recommended in France
• Bedrooms: 16 to 17 °C, a cooler temperature actually promotes sleep
• Bathroom: 21 to 22 °C only while in use, otherwise keep it around 17 °C
• Kitchen: 18 °C is enough, cooking already brings heat
• Unoccupied rooms (hallways, storerooms): 16 °C or frost-protection mode during prolonged absence

How much do you save by lowering the heating?

The order of magnitude often quoted by energy organisations is around 7 % saved on the heating bill for every degree the temperature is lowered. It is an average estimate: the real figure depends on the quality of the insulation, the size of the home and the type of heating. Going from 21 °C to 19 °C in the living rooms can therefore represent savings of around 10 to 15 % on the heating share, without feeling a loss of comfort once the adaptation period is over. Note, however: these orders of magnitude assume reasonable temperatures, not freezing rooms that would push you to use an energy-hungry space heater.

Programming the temperature reductions

A good setting is not limited to a fixed target: it alternates comfort periods and eco periods. At night, a reduction to 16-17 °C for 8 hours is generally advised. During the day, if the home is empty for more than a few hours, programme a reduction to 16-17 °C in eco mode. With a programmable thermostat, the heating comes back on automatically 30 to 60 minutes before your alarm or your return, depending on the inertia of the building. For absences of several days, favour the frost-protection mode (about 8 °C): coming back to a house at 8 °C is bearable, and the warm-up is faster than after a total shut-off which has also let the walls cool down.

The right settings on a smart thermostat

• Activate the occupancy or motion detection if your model has it: it avoids heating an empty house
• Use the optimisation (learning) function which remembers how long the home takes to heat up
• Set the target room by room if you have thermostatic radiator valves as a complement
• Check that the sensor is not influenced by a radiator, a window or a heat source
• Remember to programme weekend scenarios if your occupancy times change at the end of the week

Thermostat and humidity: finding the right balance

A poorly ventilated house accumulates humidity, which gives a feeling of cold that pushes you to turn up the heating. Air each room for 5 to 10 minutes a day, even in winter, to renew the air without letting the walls cool down. In the bathroom, switch on the extractor fan and dry the room after the shower. A comfortable felt temperature also depends on the humidity: between 45 and 60 % relative humidity, you feel good at 19 °C, whereas with air that is too dry or too damp, the same temperature feels unpleasant.

The mistakes to avoid

• Placing the thermostat near a window, a radiator or the television: the reading is skewed
• Completely switching off the heating during a winter absence: risk of the pipes freezing
• Bumping the target up suddenly to heat faster: the boiler does not go any faster, it just consumes more
• Setting the thermostat to 23 °C hoping to dry out a damp home faster
• Ignoring the thermostatic radiator valves: they usefully complement the main thermostat in little-used rooms

Setting your heating thermostat correctly ultimately comes down to three moves: choosing temperatures suited to each room, programming reductions at night and during absence, and making sure the sensor measures the room temperature correctly. These settings, combined with good ventilation and careful insulation, translate into real savings on the bill, without degrading comfort. If your thermostat is old or awkward to use, replacing it with a programmable model remains one of the most profitable investments in the home.