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Chimney stove performance in the check - What do kilowatt figures mean?

If you want to buy a wood-burning stove, you can choose from a wide range of models and different kilowatts, and questions are often asked such as:

  • How many kW does my stove need?
  • Can I heat my house with a wood-burning stove?
  • What does kW mean? What is the heating power?

The specification of kilowatts (kW) for a stove describes the heating output of a model. This value must be known roughly in order to be able to use the device efficiently after installation. Too little kW would mean that the desired comfortable room temperature is not reached or only slowly. A stove with too high a heat output would quickly overheat the room climate. However, performance may vary depending on the conditions. For example, in a poorly insulated house, some of the power is lost through thermal bridges.

In this article we want to inform you about what the kilowatts mean exactly and how this information is measured. You will also find other factors that play an important role when buying a wood-burning stove and how wood-burning stoves with different numbers of kilowatts differ in this article.

What can a stove do?

When choosing a stove, the kilowatt specification is important, but not the only selection criterion. What performance your stove should have is a question that arises before buying a stove. In order for this question to be answered, it is important to deal with the background. Particularly relevant for this: What are watts and why is power or nominal heat output called?

The technical terms for stove performance

The calorific value in Kilowatt hours

Kilowatt is the parameter that indicates the power of the furnace. The corresponding number kWh indicates the calorific value that can be achieved by the stove in one hour when using a certain fuel. The condition for the maximum achievable kilowatts is a heating environment in which there are no thermal bridges and no water vapor condenses in the exhaust gas. Basically, the calorific value is slightly lower in practice than the kilowatt indication on the device.

Calorific value also in kWh

In order to determine the value for the gross calorific value, it is determined under laboratory conditions, how much energy is gained from burning a certain fuel. For this figure, energy escaping via flue gases is also taken into account.

Nominal heat output

This performance information is used to compare the performance of wood-burning stoves of different designs. During the TÜV test, the stove model was fired with exactly one kilogram of logs for a nominal output of four kilowatts. The stove in question can achieve at least this nominal heat output with exactly this amount of fuel burned. In practice, it is possible to throw in more wood or more pellets and thus achieve a temporarily higher output.

Performance range

The information on the power range summarizes the minimum and maximum achievable heating power. In between, the actual kilowatt output depends on the amount of wood, its strength and basic structure. Frequent reloading or just burning change the values.

Further selection criteria for the optimal stove

The optimum selection of a stove is not yet possible based on the kilowatt information alone. Rather, these criteria must also be taken into account:

1. Sheet iron, cast iron or soapstone - the material of the stove

Sheet iron hasn't been in use for too long as an exterior material for wood-burning stoves. However, it is practical because it heats up quickly, emits the heat quickly and cools down again quickly after the fire is over. Iron sheet can also be shaped particularly well in modern designs and the surface can be refined to be velvety or smooth. Traditionally, indestructible stoves also consist of cast iron. This material can withstand a lot of heat and has a strong storage capacity. A cast iron stove only heats up slowly, but it still warms up long after it was last fired. Anyone who would like to get the best out of heating power from a one-time firing of their wood-burning stove can use the material Soapstone choose. Soapstone is extremely decorative in any room environment. In addition, the heat of the fire from the stove does not get directly into the air, but is intensively stored in the soapstone and released from it continuously over several hours.

2. The immediate vicinity of the furnace

The stove can be set up directly on a tiled floor. If, on the other hand, the floor is made of combustible materials, a floor plate must be placed under the stove. For proper fire protection (spark protection), this protective plate covers the floor at least 50 cm in front of and 30 cm to the side of the combustion chamber opening. To protect against radiation from combustible materials in the area of ​​the combustion chamber pane, at least 80 cm - better 100 cm - must be observed. The distances to the side and to the rear differ from model to model and are usually between 5 and 60 cm. However, only always to combustible material. If in doubt, the district chimney sweep should specify the specifications on site.

3. The connection to air connections (chimney)

No wood-burning stove may be operated without an existing vent. An intact chimney must therefore be able to be connected to the model via the smoke pipe without any problems. Standard dimensions for flue pipes are often 150 millimeters in diameter. If there is no chimney in the vicinity, it must first be converted accordingly. Modern conversion options are offered with prefabricated modules made of insulation, pipe and outer shell. Stainless steel external chimneys also offer a perfect solution here.

Advantages and disadvantages of low or high kilowatts of power

A stove with a low kilowatt output is ideal for small rooms and only occasional use. If longer heat storage is desired, it should consist of a storable body. If more emphasis is placed on the cozy crackle and the sight of the flames, a model with a large viewing window and a body made of sheet iron is sufficient. As soon as several rooms are to be heated, a higher heating output is necessary. A water-bearing stove can be useful for this purpose. It uses every watt of heat particularly efficiently. If the kilowatt output of the stove is too high, an uncomfortable room climate will quickly develop. This has to be improved by ventilation, which means that a lot of energy is lost again.

The comparison: stoves of the same model series with different performance

In order to address the differences precisely, we would like to place two chimneys in the same row opposite each other. We have decided here to compare the SCAN 83-4 Maxi stove with 5 kilowatts and the SCAN 85-1 stove with a low base and top with 8 kilowatts.

The stove SCAN 83-4 Maxi (5kW)

The Scan 83-4 Maxi stove with a specified Output of 5 kW is ideal for heating rooms 50 to 260 sqm. Depending on the type and intensity of the lighting, a power range between two and seven kW can be used. The heat is emitted very evenly via the soapstone cover plate and several heat storage stones for up to 12 hours after the last wood was laid.

The SCAN 85-1 stove with low base and top (8 kW)

In contrast to the above model with 5 kW, the SCAN 85-1 stove with its 8 kW power only from a room size of 75 to 380 sqm recommendable. The average heating output varies between three and ten kW, depending on the type and quantity of the firewood. It should be noted that due to the high output, a greater safety distance to walls, furniture and combustible equipment in the vicinity of the stove must be maintained compared to the SCAN 83-4 model.

The kilowatt conclusion

The specified output in kW for wood-burning stoves is an average value that is determined under laboratory conditions. In practice, various factors determine how much of the possible heating output can be used. A stove with a minimum output times ten of the existing room size is ideal. Visit our shop and filterNominal heat outputto find the right stove for you: