Short answer: at 0.15 €/kWh an inverter air conditioner heats more cheaply than a wood stove if a stacked cubic metre of firewood costs more than 36–44 €. Below that price the stove wins. For a 25 m² room in Varna, a season with an air conditioner comes to about 82 € of electricity, and with wood at 60 € per cubic metre to between 110 and 136 €.
The question usually comes from people who already light a stove in the living room and are thinking of adding an air conditioner. Or from owners of an old house where the stove has stood for years. The sums are the same, and if the stove and chimney are already there, you pay nothing new for them.
How we compare the two bills
We take two cases, the same as in our other heating calculations: a 25 m² room needing about 2 500 kWh of heat per season and an insulated 120 m² house needing 9 900 kWh. Electricity costs 0.15 €/kWh. The inverter air conditioner has an SCOP of 4.6, so it gives about 4.6 kWh of heat for every 1 kWh of electricity.
For firewood we use figures from the UK agency Forest Research: air-dry logs at 20 % moisture give 1 400–2 000 kWh per stacked cubic metre. We take an average of 1 700 kWh. Regulation (EU) 2015/1185 requires a new closed wood stove to reach a seasonal efficiency of at least 65 %. Better models reach about 80 %, so we calculate both.
The price of firewood is the least certain part. In listings for Varna and the surrounding area in October 2026, firewood is offered at between 30 and 72 €, and the ads often do not say whether the price is per stacked cubic metre, for metre-long logs or for split wood. We calculate three levels: 40, 60 and 80 € per stacked cubic metre.
A 25 m² room: the seasonal bill
| Option | Fuel per season | Cost |
|---|---|---|
| Air conditioner, SCOP 4.6 | 543 kWh of electricity | 82 € |
| Stove 65 %, wood at 40 € | 2.3 stacked m³ | 90 € |
| Stove 65 %, wood at 60 € | 2.3 stacked m³ | 136 € |
| Stove 65 %, wood at 80 € | 2.3 stacked m³ | 181 € |
| Stove 80 %, wood at 40 € | 1.8 stacked m³ | 74 € |
| Stove 80 %, wood at 60 € | 1.8 stacked m³ | 110 € |
| Stove 80 %, wood at 80 € | 1.8 stacked m³ | 147 € |
With cheap wood and a good stove the two bills are almost equal. The wood even wins: 74 € against 82 €. At 60–80 € per cubic metre the air conditioner comes out 28–99 € cheaper per season, and that is for one room only.
A 120 m² house
| Option | Fuel per season | Cost |
|---|---|---|
| Air conditioners in the rooms, SCOP 4.6 | 2 152 kWh of electricity | 323 € |
| Stove 65 %, wood at 40 / 60 / 80 € | 9.0 stacked m³ | 358 / 538 / 717 € |
| Stove 80 %, wood at 40 / 60 / 80 € | 7.3 stacked m³ | 291 / 437 / 582 € |
For a whole house the gap grows: at 60 € per cubic metre the wood costs 437–538 € per season against 323 € of electricity. A single stove also rarely heats 120 m² evenly. The room with the stove is hot, the bedrooms stay cool. We have set out the whole-house model in detail in how much electricity a heat pump uses, where air conditioners are included too.
The wood price at which the stove wins
One kWh of heat from the air conditioner costs 0.15 : 4.6 ≈ 0.033 €. One kWh from the stove is the price of a cubic metre divided by 1 700 kWh and by the efficiency. The two are equal at about 36 € per stacked cubic metre if the stove is 65 % efficient, and at about 44 € if it is 80 %.
The threshold depends on the wood. With heavy, well-dried wood (about 2 000 kWh per cubic metre) it rises to 42–52 €, with light or poorly dried wood it falls to 30–37 €. It also rises with dearer electricity: at 0.20 €/kWh it is about 48–59 €.
What the price per cubic metre leaves out
The tables count fuel only. A stove also brings work: you cut and split the wood, carry it to the stove, light it every day and clear out the ash. If you would rather not do this yourself, you pay separately for cutting and splitting.
You also need a dry place to store it. Wet wood gives less heat, because part of its energy goes into evaporating the water, and then the figures above no longer hold. Add chimney cleaning as well. With an air conditioner what remains is maintenance, usually once a year.
When a wood stove makes sense
If you have your own wood or buy it below 36–44 € per cubic metre, the stove is cheaper on fuel. It is also useful as a back-up during power cuts, because an air conditioner does not work without electricity.
The two work well together. The air conditioner handles everyday heating, and the stove is lit on the coldest evenings. You need less wood per season, and handling it becomes a rare job.
An air conditioner for heating one room: capacity and price
For 15–25 m² a 9000 BTU air conditioner is enough, for 25–35 m² a 12000 BTU one. In the catalogue, 9000 BTU models start from 300 €, and 12000 BTU ones from 315 €. Standard installation in Varna of a unit up to 14 000 BTU bought from us costs 150 € (up to 3 m of piping).
If the air conditioner with installation costs you 450 € (a 300 € model plus 150 € standard installation) and replaces a stove burning wood at 60–80 €, it pays for itself from the fuel savings in 5–16 seasons. The payback is shorter if the wood is expensive and the stove is old. For heating, check two figures in the data sheet: the SCOP and the lowest outdoor temperature at which the unit still heats. There is more in air conditioner for heating and in the SCOP ranking. If you are comparing with a convector or an oil radiator, the sums are in cheap electric heating, and for a house with a boiler in heat pump or pellets.
Frequently asked questions
Which is cheaper for heating: an air conditioner or a wood stove?
At 0.15 €/kWh the air conditioner is cheaper if a stacked cubic metre of firewood costs more than 36–44 €. For a 25 m² room a season with an air conditioner is about 82 € of electricity, and with wood at 60 € per cubic metre 110–136 €.
How much wood does one room need for the winter?
A 25 m² room needing about 2 500 kWh of heat per season takes 1.8–2.3 stacked cubic metres of dry wood, depending on the stove’s efficiency.
How much electricity does an air conditioner use heating a room all winter?
About 543 kWh for 25 m² at SCOP 4.6, which is about 82 € at 0.15 €/kWh. For other floor areas see how much electricity an air conditioner uses.
Does an air conditioner heat in sub-zero temperatures in Varna?
Yes. Winters in Varna rarely drop below 0…−7 °C, and the inverter models in the catalogue heat down to −15 °C, some down to −25 °C.
Can an air conditioner and a stove work together?
Yes. The air conditioner keeps the temperature every day, and the stove is lit in the hardest frost. You burn less wood per season and light the stove less often.
