Air conditioner as heating: when does it pay off?
A modern air conditioner does not only cool; chosen well, it can also be an inexpensive source of heat. It has limitations you should know about, though.
How an air conditioner heats
An air-to-air air conditioner is essentially a heat pump. It moves heat from the outdoor air into the room and uses electricity to do so. That is why it delivers several kWh of heat from 1 kWh of electricity. The calculator uses the same assumption for it as for a heat pump: a COP of 4.5.
What heating with an air conditioner costs
With the calculator's default values, 1 kWh of heat from an air conditioner costs about €0.044/kWh, and the yearly cost for a heat need of 15,000 kWh is €667. Gas heating costs €1,708 in the same example.
| System | Assumption | Default price | Price of 1 kWh of heat | Per year at 15,000 kWh |
|---|---|---|---|---|
| Air conditioning | COP (coefficient of performance) 4.5 | €0.20/kWh | €0.044 | €667 |
| Heat pump | COP (coefficient of performance) 4.5 | €0.20/kWh | €0.044 | €667 |
| Gas | calorific value 10.5 kWh/m³ at 92% condensing boiler efficiency | €1.10/m³ | €0.114 | €1,708 |
| Direct electric heater | 98% conversion efficiency to heat | €0.20/kWh | €0.204 | €3,061 |
Limitations to be aware of
- Output drops in frost. At very low outdoor temperatures, both output and COP fall, and every model has a minimum temperature at which it can still heat.
- An air conditioner warms the air, not the walls and floor. The feeling of warmth differs from radiant heating.
- Most units cannot heat domestic hot water.
- The indoor unit is audible and the outdoor unit is noisy, which matters when deciding where to put them.
- A house with a complex layout or many rooms needs more indoor units, which raises the purchase price.
Who an air conditioner as heating suits
It works best in flats and smaller houses, as a supplementary source in the shoulder seasons (spring and autumn), or where only electricity is available and you don't want to build a water-based heating system. As the only source of heat in a large house during hard frost, it is usually less suitable.
What to look at when choosing a model
- SCOP (seasonal coefficient of performance): the higher it is, the lower the consumption when heating.
- The minimum temperature at which the unit can still heat.
- A heated base pan on the outdoor unit, which protects against condensate freezing.
- The noise level of the indoor unit.
We compare these parameters in our table of air conditioners.
The numbers in the tables and examples are based on the calculator's default values (rough average prices for Slovakia). Real costs differ with your prices, equipment and house.
Frequently asked questions
Can you heat with an air conditioner alone?
In small, well-insulated spaces, yes. In a larger house it is usually combined with another heat source during hard frost, because the output of an air conditioner drops in the cold.
Is an air conditioner cheaper than a heat pump?
It is usually cheaper to buy. Running costs come out the same in the calculator, because it uses the same COP of 4.5. Most units, however, cannot heat hot water and they heat the air rather than a water-based system.
What does SCOP mean?
SCOP is the seasonal coefficient of performance, the average efficiency over the whole heating season. The higher it is, the less electricity an air conditioner uses for the same heat.