Vaillant geoTHERM Review - Geothermal Heat Pumps

Vaillant geoTHERM is the ground source heat pump that utilizes ground (geothermal) energy to heat water and home space during the winter or provides cooling in the summer. Its advantages over other types of water heaters are that geoTHERM uses the natural and free energy for heating, does not require the fuel storage, it is not affected by the fuel price increases and there is no impact on the environment, but the installation of the whole system might be complicated. Other benefits include the 10-year warranty on the compressor, advanced electronics for the accurate and efficient operation, monitoring and diagnostics and frequent incentives from the government and utility companies.

The Vaillant geoTHERM heat pump is bigger than the gas or electric counterparts; maximum dimension is approximately 1200x760x900 mm and maximum weight is 340 kg, for the geoTHERM exclusive model. The warranty is short, 3 years on the heat pump, but 10 years on the compressor.

Types, pros and cons

Vaillant geoTHERM heat pump

Vaillant offers two types of the heat pumps; one with the ground collector that is installed below the ground surface and heat pumps with the geothermal probe, also installed in the ground.

Both types have pros and cons, but the main difference is that the heat pump with the ground collector is cheaper than the one with the geothermal probe, but requires more space for installation and is less efficient.

The ground-energy heat pumps can operate efficiently all year round because the ground temperature is stable all the time. The indoor heat pump installation is easy, while the outside part can be complicated and does not require any extra space for the fuel storage.


The Vaillant geothermal heat pump uses a water or brine as the heat transfer medium. The operating console is simply designed and conveniently located at the front of the unit, and it utilizes the advanced electronics, LCD display and two dials which are used for programming.

The heating system is protected from freezing temperatures; when the outside temperature drops below its minimum setup value, the controller turns on the system and if the temperature in the hot water cylinder is below 10 C it gets heated to increase the temperature. Other sensors protect the system from water loss, pump and valve seizing, phase monitoring, protection against loss of brine... For the added comfort and increased reliability during the winter months, the heat pumps are also supplemented by the electric energy coming from the built-in heating element so hot water is available even when the heat pump gives an extremely low efficiency.

The geoTHERM heat pumps come in several sizes or power outputs

Depending on the size of the house that has to be heated, Vaillant offers several types and sizes. The geoTHERM heat pumps come with the heating power output range from 6 kW to 46 kW, grouped in the standard and exclusive categories.

geoTHERM exclusive

The geoTHERM exclusive series is similar to the standard type with an addition of the integrated 175 l hot water cylinder made of the durable stainless steel, the 4kW electric heater and additional cooling function for use in the summertime. Such a design allows users to get hot water fast and with the lower energy loss. The exclusive series is represented by three models; 6 kW, 8 kW and 10 kW model, all using either water (VWW models) or brine (VWS models), as the heating medium.

geoTHERM standard

The standard type of the geoTHERM series comes with the heating power output range from 6 kW to 46 kW as a single unit, or up to 92 kW when combined into the cascades. The heat pumps from the standard group are smaller because these do not have the integrated hot water cylinder as the Exclusive series and the heating element comes with the 6 kW as the backup. Heat pumps from the Standard group can be equipped with the external heating exchanger if the passive cooling is needed.


The geoTHERM heat pumps are used in residential homes or commercial buildings, so when connected to the hot water cylinder they can be used in domestic hot water production or for the radiator and underfloor heating. The heat pumps can also be combined with the solar water heating systems where the solar hot water cylinder geoSTOR will replace the integrated cylinder and therefore use both solar and ground energy for water heating.

A simple connection allows easy heat pump installation either in new homes or if upgrading or changing the existing system. The complicated part is the ground side work. Once installed, the heat pump provides efficient and reliable operation continuously. And the work can be monitored remotely while the advanced diagnostics allow easy diagnostics and troubleshooting.

The Vaillant geoTHERM heat pumps can be used all year round even if the surrounding air temperature is lower and the ground temperature is close to zero degrees. The reason is that the ground still contains useful energy, and if the surrounding temperature approaches required one inside the room, the savings are much greater.

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