This paper presents a simulation of a hybrid ground source heat pump system, performed using a new graphical user interface for HVACSIM+. Hybrid ground source heat pump systems incorporate both ground loop heat exchangers and supplemental heat rejecters, such as cooling towers, cooling ponds, or pavement heating systems. HVACSIM+ capabilities have recently been extended by the addition of ground loop heat exchanger models, water-to-water and water- to-air heat pump models, pavement heating system models, and heat rejection pond models. New component models are discussed and a hybrid ground source heat pump system with heated pavement as a supplemental cooler is simulated using the visual modeling tool. First, though, an introduction to a new graphical user interface for HVACSIM+ is given. The user interface that originally came with the program could not be characterized as user-friendly. The new graphical interface allows users to develop system models by hooking components together. Provisions for controlling the simulation, setting the component parameters, editing the boundary file and plotting the output are also included.