The Aletschspa in Switzerland is a modern spa and wellness centre located in Naters, Switzerland in the heart of a UNESCO world natural heritage site. Aletschspa is built with the aim of adding value to the hotel through high standards of construction and design. The combination of energy savings and increased comfort enjoyed by guests will result in a faster return on investment.

The Hotel Spa is heated by two inverter-driven ground-source heat pumps of around 10 °C with demand on average of 100 kW. Cooling (air-conditioning) is provided by passive cooling, and domestic hot water is provided by a compact heat transfer station.

The heating system covers floor heating as well as pool and floatation pool heating. The heated area is 1 500 m2. As a renewable solution, two Thermia Mega ground-source heat pumps are used with a capacity of 14-59 kW which are driven by inverters.

Cooling (air-conditioning) is provided by passive cooling, which means that energy to cool the facilities comes from the groundwater. The installation features a cold buffer tank with a volume of 1 872 litres.

Domestic hot water is provided by a compact heat transfer station mounted on one of the tanks. The primary side uses returned (re-used) hot water to heat the clean domestic water. The advantage is that the inverter technology, heat transfer station, and hot gas technology combine to provide more hot water at a higher temperature. This removes the need for a hot water tank and eliminates potential problems with legionella bacteria as all hot water is produced ‘just in time’.

The heating system includes a hot buffer tank with a volume of 1 950 litres, known as 'combi' boiler. The upper part is heated by the hot gas supply line from the heat pump while the lower part is charged by the heating supply line. This buffer tank is designed to reach optimum layering across the whole tank. The upper part reaches over 70° C and the lower part between 40° C and 35° C, which is enough to serve the heating system. Two combi boilers were installed in the Aletschspa to increase volume.