This paper presents an innovative building comprising a heat pump connected to a solar roof and a geothermal heat exchanger. This unit is able to invert its cycle and operate as an Organic Rankine Cycle (ORC). The solar roof is producing large amount of heat throughout the year. This allows covering the building annual heating needs and, furthermore, electricity is produced thanks to the surplus of heat in a so-called HP/ORC reversible unit. This paper focus on these three main points: sizing, experimentation and simulation of the reversible unit. First, an optimal sizing of the components and fluid R134a shows promising performance with a net electrical energy produced over one year reaching 4030 kWh. Following that, a prototype has been built and has proven the feasibility of the technology. Finally, a simulation code including the building, the ground heat exchanger, the thermal energy storage, the solar roof and the reversible HP/ORC unit is developed and allows to perform a sensivity analysis. Annual results show that this technology leads to a Positive Energy Building.