In the autumn of 2000, the British Engineering Council awarded an Environmental Engineering award to the groundsource heatpump project at Commerce way, Croydon Surrey. This largest UK groundsource project is a speculative built industrial building of about 3000 m² with both offices and warehouse facilities. The building, that is occupied by Ascom Hassler Ltd. (a Swiss based IT company), is expected to have an annual cooling load of 100 - 125 mWh and a heating load of 90 – 100 mWh. Peak loads under hot summer conditions are anticipated to reach up to 130 kW. During the normal life span of a building (25 years) the surplus of heat would lead to higher ground temperatures. This leads to less efficient heat pump operation and may result in insufficient capacity during cooling peak demands. As a solution a hybrid system, incorporating a dry-cooler, was developed. The principal idea was to use the dry-cooler to store cold in the wellfield during early spring, when the required summer peak load cool can be generated very efficiently and cheaply. The operation and efficiency of the wellfield, the installed heat pump system and dry-cooler is controlled and monitored under a Building Management System (BMS). The results of the first year of operation of the system are presented. Using the monitoring data an evaluation of the original design can be made.