7 rules for using your air conditioner efficiently in winter
- Set temperature 20-22 °C: every degree you raise increases consumption. Setting it to 30 °C does not heat the room faster; it only makes the unit run at full power for longer.
- Keep it steady: an inverter air conditioner runs at low speed once it reaches the set value. Instead of turning it off for short outings, lower it by 2-3 degrees.
- Point the louvers downward: hot air rises; air blown downward heats the room more evenly.
- Leave the fan on auto: the unit adjusts the fan itself so that it does not blow cold air.
- Clean the filters every two to three weeks: a clogged filter noticeably reduces heating capacity.
- Keep the front of the outdoor unit clear: snow, leaves and covers block airflow. If the unit gets buried in snow, a raised bracket is needed.
- Keep doors and windows closed, close the curtains at night: heat lost through the glass increases the load on the air conditioner.
Air conditioner not heating: possible causes
| Symptom | Likely cause | What to do? |
|---|---|---|
| No air for a few minutes at startup | Normal: the fan waits so as not to blow cold air until the indoor unit coil warms up | Wait 3-5 minutes |
| Hot air cuts out from time to time while running, indoor unit light blinks | Defrost (ice melting) cycle | Normal; heating returns after 5-10 minutes |
| Air is lukewarm | Dirty filter, dirty coil, wrong mode (auto/dry) or low set value | Check the mode and the filter |
| No hot air at all, outdoor unit is running | Low refrigerant, 4-way valve fault, sensor fault | Call for service |
| Outdoor unit does not run at all, there is a code on the display | Electrical, board or communication fault | Note the code and pass it on to service: air conditioner error codes |
| Not enough on very cold days | The unit's capacity drops at low temperatures, or it was sized too small for the room | Capacity check; supplementary heating if needed |
Why does the outdoor unit ice up, and what is defrost?
In heating mode, the coil in the outdoor unit is colder than the outside air; moisture in the air condenses on the coil and freezes when the air is around 0-5 °C. The air conditioner detects this with its sensors and reverses the cycle for a few minutes to warm the coil; this is called defrost . During this time, steam and water coming from the outdoor unit and the indoor unit stopping its airflow are normal.
The following, however, are not normal: the outdoor unit turning into a solid block of ice, defrost never ending or repeating too often, melt water freezing under the unit and reaching the coil. These point to a sensor, refrigerant amount or drainage problem. Make sure the melt water under the outdoor unit is drained to a safe place; icing on walkways in particular is dangerous.
Is heating with an air conditioner economical?
On mild and cool days, a good inverter air conditioner often produces its heat more cheaply than natural gas; the advantage shrinks as the outdoor temperature falls below zero. We explained step by step how the calculation changes with the tiered natural gas tariff in our article is heating with an air conditioner cheaper than natural gas. For a comparison with an electric heater, see our article electric heater or air conditioner.
Is your air conditioner heating efficiently in winter?
Tell us the model, the room size and the problem you are having; for maintenance or a fault, we will get back to you the same day.
Pre-winter maintenance
Dust that builds up over the summer also reduces heating efficiency in winter. Filter cleaning, indoor unit coil and fan cleaning, an outdoor unit check and refrigerant pressure measurement in the fall get your air conditioner ready for winter. Details: air conditioner maintenance and air conditioner gas charging.
Frequently asked questions
What temperature should an air conditioner be set to for heating?
For most people, 20-22 °C is comfortable. A higher set value increases consumption and does not heat the room faster.
Why does the air conditioner stop from time to time while heating?
It is most likely in defrost: it pauses heating for a few minutes to melt the ice on the outdoor unit. This is normal.
Does an air conditioner heat at below-zero temperatures?
Most inverter air conditioners work at below-zero temperatures, but their capacity and efficiency drop. Models made for cold climates work efficiently at even lower temperatures.
Should I put a cover over the outdoor unit?
Do not block the air intake and outlet of a running unit. To protect it from snow, you can use only a canopy that is open on the sides and does not cut off airflow.