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Condensing heating: advantages, disadvantages and costs
Condensing heating: advantages, disadvantages and costs

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Gas, oil or pellets? Condensing heating systems promise high savings. You should know this before installation regarding the costs as well as the advantages and disadvantages of heating technology.

Table of contents Table of contents condensing heating: advantages, disadvantages and costs at a glance

  • How does condensing heating work?
  • What types of condensing heating systems are there?
  • Calorific value or calorific value: which is more important?
  • What are the requirements for installation?
  • Advantages of condensing heating
  • Disadvantages of condensing heating
  • What does condensing heating cost?
  • What funding is there?

Table of contents Table of contents condensing heating: advantages, disadvantages and costs at a glance

  • How does condensing heating work?
  • What types of condensing heating systems are there?
  • Calorific value or calorific value: which is more important?
  • What are the requirements for installation?
  • Advantages of condensing heating
  • Disadvantages of condensing heating
  • What does condensing heating cost?
  • What funding is there?

Modern, energy-efficient condensing heating can save you up to 15 percent on heating costs. You can even reduce your carbon footprint by 50 percent and more. But many still shy away from replacing and expanding their old heating technology. Why? The answer is probably the comparatively high cost of purchasing and installing a condensing heating system. Experts generally recommend a more modern boiler after 15 years at the latest. Anyone renovating or planning a new installation will usually not be able to avoid a modern heating system anyway. For some years now, manufacturers have only been able to sell models that are not less than 86 percent efficient. The only exception are older stocks.

How does condensing heating work?

Older heating systems work exclusively with the energy that is generated when the fuel is burned. You literally shoot a lot of energy out of the chimney. After all, the combustion of oil, gas or wood produces, among other things, water vapor, carbon dioxide, but also carbon monoxide, nitrogen oxides or sulfur dioxide. All of this is conducted outdoors - without any further benefit. Modern condensing heating has a completely different approach. It focuses on the recycling of exhaust gases. The temperature of the exhaust gases is lowered so that the hot steam condenses. Heat is generated, which in turn can be used by the heating system. The exhaust gases can be cooled, for example, by heating water that has already cooled down in the return to the boiler.

What types of condensing heating systems are there?

When choosing the right condensing heating system, you have the choice between oil, gas and pellets. Regardless of the fuel, condensing heating always works on the same principle: it uses the additional energy hidden in the exhaust gases and can therefore work far more efficiently than conventional heating systems. As a rule, all three systems can be combined well with renewable energies. And: They burn almost losslessly at around 98 percent. However, you should note that each condensing heater has a different maximum output. You should also note the standstill losses specified by the manufacturer.

1. Gas condensing heating

About half of Germans rely on gas heating. However, a connection to a gas network is required for this. Even if you do not use the heating, there are costs in the form of basic fees. You are also bound to a provider and their prices. In some regions there are suppliers of bio gas, which partly consists of renewable raw materials.

2. Oil condensing heating

Oil heaters are also popular in Germany because they have proven themselves for a long time. The advantages: You only buy oil when you need it or when the price is cheap. However, you must store the oil in an oil tank. And that takes up space. However, modern systems are somewhat more compact than the large old boilers. There is also the option of using bio heating oil.

3. Pellet heating

Condensing boilers that use pellets are considered to be particularly environmentally friendly. The wood that you burn here in the form of small sticks breaks down as much CO2 when it grows as it releases later when it burns. The CO2 balance is particularly good here. In addition, 90 percent of the pellets consist of wood waste from the manufacturing industry. As with oil, this heating technology requires additional space for storing the fuel. In addition, maintenance and cleaning for pellet heating systems are more complex than for other systems - for example due to the ash that is created. There is also more fine dust than when burning oil or gas. Pellet heaters are comparatively expensive. That should be one of the reasons why they are not yet as widespread as other types of condensing heating.

Pellets
Pellets

Pellet heating has a particularly good environmental balance.

Photo: iStock / Irina Vodneva

Calorific value or calorific value: which is more important?

If you are looking for the ideal condensing heating system for you, you will find various information about the condensing value and the calorific value. The degree of utilization is sometimes given as over 100 percent. This is of course a handball trick. Because boilers cannot burn more energy than is supplied to them. The calorific value and the calorific value are often used synonymously. That is also not correct. The calorific value is the thermal energy that is generated when a fuel is burned. With older heating technologies this can be less than 70 percent. So around 30 percent of the energy is not used here. With more modern systems, usage can reach 90 percent. But you also do without energy here. Now the calorific value comes into play. This corresponds to the calorific value plus the heat of condensation that arises with condensing heating. This gives you 98 percent energy efficiency. However, some manufacturers assume the maximum use for the calorific value. The heat of condensation is counted here as a plus, so that values ​​of over 100 percent arise.

What are the requirements for installation?

Before you decide on a new condensing heating system, you must first calculate the heat requirement. It is not uncommon for homeowners to pay unnecessarily a lot because their boiler is oversized. In this case, the consumption was mostly only estimated. This means, for example, that you pay more basic fees to some gas suppliers, as these depend on the installed capacity. Installers or energy consultants who are subsidized by the state help to choose the right size. When installing condensing heating, you must always observe the following:

  • A waste water connection must be available in order to discharge the condensation water into the sewage system. Usually this is not a problem.
  • The acidic condensate must be neutralized if the sewage pipes are not acid-resistant.
  • The chimney must be resistant to acid and moisture. Usually this can be done with a flue pipe made of stainless steel or plastic.
  • A fan is often required to remove the exhaust gases, since the lower exhaust gas temperatures reduce the chimney effect in the case of condensing heating.
  • Hydraulic balancing is required for grants.
Öltank
Öltank

The oil for an oil condensing heating system should be stored in a safe heating oil tank.

Photo: iStock / Vladdeep

Advantages of condensing heating

  • Depending on the project, model and use, energy savings of up to 30 percent are possible.
  • Condensing heating enables efficient use of energy.
  • There are fewer pollutant emissions.
  • There are space-saving models.
  • The installation of condensing heating systems is usually also possible without problems in older houses.
  • Condensing heating is subsidized by the state.
  • The heating can be combined with renewable energies.

Disadvantages of condensing heating

  • Condensing heating systems are more expensive than other heating systems.
  • Combustion gases and the resulting condensate are acidic, so that suitable waste water pipes and exhaust pipes must be available.
  • Additional work on the chimney is often necessary.

What does condensing heating cost?

Condensing heating systems are more expensive to buy than conventional heating systems. The costs depend on the size, performance and fuel of the boiler. There are also installation costs of an average of 2, 000 to 3, 000 euros. However, there may also be costs for chimney renovation, gas or sewage connections, hot water storage tanks and hydraulic balancing. Combine your condensing heating with renewable energies, the costs increase again. A price comparison:

  • Oil condensing heating: around 6, 000 to 9, 000 euros
  • Gas condensing heating: around 5, 000 to 10, 000 euros
  • Pellet condensing heating: around 15, 000 to 20, 000 euros
  • Average total costs: 10, 000 to 15, 000 euros

What funding is there?

Both the Kreditanstalt für Wiederaufbau (KfW) and the Federal Office of Economics and Export Control (BAFA) offer grants for condensing heating. It is important that you apply for funding before signing a contract with an installer. KfW supports gas heating and oil heating with the 420 program in the amount of 15 percent up to a maximum amount of 7, 500 euros. Pellet heating systems are funded by the BAFA with around 3, 000 to 5, 000 euros.

Anja Schmidt

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