A Geothermal Energy system was installed in a 140m² office building to provide heating, cooling and hot water. A gas boiler was replaced by a geothermal heat pump with a nominal heating capacity of 9KW and a COP of 4.3 at B0/35. The system was equipped with a 17 KW passive cooling unit and a 180-litre tank for hot water. The heating and cooling was via the existing underfloor heating system.