Reversible air conditioner in winter: setting it up for heating, or putting it to rest properly
The ClimatisateurPro team
8 Nov 2026 - 04 min read
When the cold arrives, owners of a reversible air conditioner ask themselves two questions: should it be used for heating, and if so how, or is it better to leave it idle until spring? Both choices make sense. What matters is doing either one properly, so that the unit gets through the winter undamaged and restarts without any unpleasant surprise.
A reversible air conditioner is an air-to-air heat pump
In heating mode, the unit reverses its operation: it captures heat present in the outdoor air, even when cold, and releases it indoors. It uses electricity to move that heat, not to produce it, which is why it delivers more heating energy than it consumes. This seasonal performance is shown by the SCOP on the energy label.
Efficiency falls as the outdoor temperature drops. Each model has a heating operating range, stated in its manual. In Île-de-France, where winters are generally mild, most recent units heat without difficulty for most of the season.
Option 1: heating with your air conditioner
The setpoint
Article R. 241-26 of the French Energy Code sets 19 °C as the upper limit for the average heating temperature in a home. ADEME recommends the same value in living areas, and a lower temperature in bedrooms. Set the remote control accordingly, bearing in mind that the displayed value is measured at the indoor unit, often mounted high up, where warm air collects.
Good habits
- Point the louvres downwards: warm air naturally rises, so it needs to be sent towards the floor. This is the opposite of the summer setting.
- Avoid frequent stops and starts: a heat pump works better at a steady pace. At night or during a short absence, lower the setpoint rather than switching off.
- Use frost-protection mode if your model has one (often around 8 or 10 °C) for an absence of several days, rather than letting the home cool down completely.
- Schedule heating periods if the unit or its app allows. A smart thermostat compatible with your model can help, provided you check compatibility before buying.
What is normal
In cold, damp weather, the outdoor unit's coil can frost over. The unit then starts a defrost cycle: the indoor unit stops blowing for a few minutes, and the outdoor unit may give off steam and water. This is designed in by the manufacturer and is not a sign of a fault.
Air heated by an air conditioner can feel dry. An indoor thermometer and hygrometer tells you whether humidity is really dropping too low; airing the room for a few minutes every day remains essential anyway.
Servicing continues in winter
Filters also get dirty in heating mode: keep washing them every two to four weeks. A sour smell when heating is first switched on usually indicates deposits on the coil; we explain what a clean with disinfection changes in our article on allergies, dust and air conditioner cleaning.
Looking after the outdoor unit
In heating mode, the outdoor unit produces water, especially during defrosting. A few precautions:
- keep drainage clear under the unit: no piled-up dead leaves, no overflowing tray;
- stop water freezing on a walkway: if the unit sits above a path or a busy balcony, mention it during servicing so that drainage can be looked at;
- clear snow blocking the fins, by hand or with a brush, never with a sharp tool or hot water;
- never cover a running unit: it needs its full heat-exchange surface.
Option 2: putting your air conditioner to rest for winter
If you have another heating system and do not plan to use the unit, a few steps are enough:
- Dry the indoor unit: on a dry day, run it on fan only for one or two hours, so that the coil and tray do not stay damp for months.
- Clean the filters, let them dry completely, then refit them.
- Close the louvres by switching the unit off with the remote control.
- Follow the manual for the power supply. Some manufacturers recommend leaving the unit powered, notably to keep the compressor warm; others allow switching off at the breaker. If you switch off, many manuals ask you to restore power several hours before restarting.
- Remove the batteries from the remote control so they do not leak.
- Clear the outdoor unit and its surroundings.
An outdoor unit protective cover can protect the top of the unit from leaves and bad weather during a long shutdown. Choose one that covers the top while letting air circulate, to avoid condensation, and always remove it before switching back on.
In spring: restarting in good conditions
Before first using cooling, check that the outdoor unit is clear, put batteries back in the remote control and allow the power-up time stated in the manual. Annual servicing is ideally done before the hot season: late winter and early spring offer more choice of slots than midsummer.
Our active vigilance saves you from having to remember: we get back in touch before the season, and before a leak-check due date if your installation is subject to one.
When to call a technician
Some signs are not a matter of settings:
- the unit blows cold air in heating mode, beyond a defrost cycle;
- the outdoor unit stays encased in ice that does not melt between cycles;
- an error code appears or the unit repeatedly shuts itself down for safety;
- water runs from the indoor unit.
In these cases, our air conditioning repair service generally comes out within 24 to 72 hours depending on the season, and no repair goes ahead without your written approval of a quote. For routine servicing in your home or your business, the price is shown in advance (€130 including VAT for one indoor and one outdoor unit, with no travel charge in Île-de-France) and you choose your slot on the booking page.
Entrust your air conditioner to an attentive technician
