Project: From gas to gas hybrid

Modernising heating systems in older buildings

Single-family house modernisation

  • You live in a detached house from the 1980s and would like to modernise the heating system. They already had the current low-temperature boiler replaced in the 1990s - but it is now at the end of its service life again.

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  • The modernisation should cost as little as possible and be realisable in a short time.

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New hybrid gas boiler

Klaus and Gabi want to modernise the heating system inexpensively and basically want to stay with gas as a fuel. They are considering combining gas with solar heat. Read on to find out what products the couple chose in the end.

Klaus and Gabi are planning their new heating system

The couple will retire in the near future and want to upgrade their home judiciously and simply. The first job is to replace the heating system. Their small house was built at the beginning of the 1980s and is accordingly poorly insulated.


Serious investment would be needed to prepare the house for using exclusively renewable heat. Until now, Klaus and Gabi have heated their house using gas, and they wish to continue doing so.

Challenges of the modernisation project

As they already have a gas connection that was used for the old heating system, they wish to keep using it. However, they must first have their chimney inspected to check whether it is suitable for modern gas condensing technology. Furthermore, they will have to decide whether to combine the new gas boiler with a solar thermal system.

Woman with bill in hand and calculator

Reasons for choosing the new solution

The cutting-edge gas condensing boiler can replace the old low-temperature boiler without any trouble. The only change required is that a new exhaust pipe has to be fitted in the chimney. There is no need for an LPG tank as the house is connected to the gas mains.


01. Quick and inexpensive conversion

The old boiler can be replaced quickly and easily because the new model can use all the existing connections. The new boiler is comparatively light and compact in size, which makes it easy to position. It is also low in price compared to other types of heating. The new boiler guarantees that no major repairs or further replacement will be required during the coming years.


02. Heating efficiently and ecologically

Condensing technology is much more efficient than earlier non-condensing technology. This saves fuel and lowers heating costs.

Combining it with solar thermal technology, which in this case could handle DHW heating for the household, saves yet more money. Furthermore, a hybrid system emits far less CO2 overall than if the gas condensing boiler alone was running the heating system and DHW heating.

Couple looking at smartphone

03. No problems concerning installation space

Klaus and Gabi need a buffer cylinder to allow them to use the heat generator efficiently. Both appliances fit in the existing boiler room without any trouble.

Klaus and Gabi find their product combination

The couple trust their heating contractor of many years and, following his advice, decide on a combined system including solar thermal technology. After all, the south-facing roof of the house has enough space for a couple of modules. Their expert mainly uses products made by WOLF, a partner of many years. On this basis, Klaus and Gabi select the following appliances:

WOLF Gas boiler TGB-2

TGB-2-20 gas condensing boiler

This model boasts energy efficiency class A and is one of the top products in its category. Furthermore, it is quiet, compact and takes up very little space.

WOLF flat-plate collectors F3-1 and CFK-1

F3-1 flat-plate collector

Klaus and Gabi choose these popular collectors for running their solar heating system.

WOLF combi storage tank

BSH high hygiene cylinder

Both systems are linked via a buffer cylinder. The high hygiene cylinder is perfect for the task. 

Ideal solution for Klaus and Gabi

The couple are pleased to have found a solution for their new heating system with the help of their heating contractor. The new system was inexpensive and quick to install. The new boiler is much more efficient than the old appliance. It saves fuel and, consequently, cuts heating costs. Furthermore, it emits less harmful CO2.


All these effects are intensified still further by the proposed combination with a solar thermal system. This uses free solar heat to heat the domestic hot water, which lightens the load of the heating boiler. The result: even lower fuel consumption and fewer emissions.

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