Renewing a heating system – why, when and how?

According to a 2019 study by the Federal Association for Energy and Water Management (BDEW), one in four heating systems in Germany is considered outdated. The fear of high costs and the effort required for conversion discourages users from renewing their heating systems. In many cases, however, this is urgently needed, whether due to the age of the system or an insufficient energy balance. Those who hesitate often experience exactly what they had wanted to avoid – high heating costs and bills for the repair and replacement of defective parts or the replacement of the heating system through necessity. This guide provides an overview of how this can be prevented. Find out about the right time to replace a heating system, the planning effort required and the costs.

Heating system renewal – starting where it makes a difference

According to the North Rhine-Westphalia Energy Agency and others, heating and domestic hot water account for an average of 70 percent of household energy costs. Consequently, renewing a heating system can pay for itself after a short time, even if it is a financial challenge. State subsidies can help to make the measure cost effective. To be eligible for these, renewable energies need to be included. This is because the state supports precisely those heating systems that allow heating with renewable energies. Over time, these not only benefit your wallet, but also the environment.

When should I renew my heating system?

You don't have to wait for the perfect moment to renew your heating system – spring, summer and autumn are all equally suitable. The obvious benefit of replacing a heating system outside of the heating season is that there is more time for improvements; measures can be completed before the colder months arrive. But a heating system replacement is also possible in the winter months, and can usually be done within one to three days. Aside from these factors, it is mostly a matter of keeping an eye on one's own cost drivers and checking in advance where the weak points of the old heating system are.

In the following cases, a replacement is worthwhile:

• Boilers aged around 25 years or more
• Old boilers that have not yet broken down but are already 20 years old (installed in the 2000s)
• Oversized boilers that take up a lot of space in the boiler room and run at permanently high boiler water temperatures
• If a flue gas inspector finds fault with the flue gas values during an annual inspection (e.g. flue gas loss of more than 11 percent)
• 30-year-old constant temperature boilers are subject to mandatory replacement in accordance with the German Building Energy Law (GEG)

The right technology for renewing a heating system

Before the workmen can get started, you need to choose the right heating system. To determine which system is suitable for your renewal, you can carry out our free energy saving check in advance. In addition to the subsidies, the basic factors are the energy status of the building, its age and the space available in the boiler room.

Have an oil boiler and want a change? A pellet heating system might be worth considering. The space for the former oil tank can then be used for the pellet store. Another advantage is that replacing an oil boiler with a new hybrid system is subsidised by up to 45 percent in some cases. Planning to install a modern gas heating system? You should consider the funding guidelines of the climate protection package. These state that gas, as a fossil fuel, is only subsidised if renewable energies are integrated.

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What needs to be considered when carrying out a heating system replacement?

Once the right heating system installer has been found and the planning is completed, it's time to start the work. Renewing a heating system means having workmen in the house sooner or later, and for many owners this can temporarily limit personal comfort in their own home. But the advantages should be considered as well, as such measures have an obvious benefit and help to save energy and costs in the long term. In addition, the duration of the work always depends on the heating system chosen.

Indispensable measure: hydronic balancing

Hydronic balancing must be carried out as part of the replacement work. This measure is important so that the new Viessmann heating system can fully exploit its savings potential. In addition, balancing is usually a prerequisite for state subsidies. Hydronic balancing of all radiators ensures that the heating surfaces are supplied with heat evenly and that the output corresponds to the respective radiators and the heating system. Hydronic balancing is only carried out by a contractor, who will set the flow rate precisely at the thermostatic valve. In many cases, valves also need to be replaced.

Compare costs – renewing a heating system is actually worthwhile

Once all the measures have been completed and the heating system and radiators have been carefully adjusted, you can finally see how your new boiler compares to the old one. Whether you will actually save as much fuel and as much on your heating costs as you had planned before the renewal is not something that can be answered in general terms. Individual heating behaviour and the average temperatures in the year in question play a role, and we don't have much influence over the latter. However, every individual can respond to external factors with cost-conscious heating behaviour. A renewed and properly adjusted heating system makes this an effective approach. In the end, it is always worth taking the courageous step of renewing your heating system.