The Rooftop Building is equipped with a building energy system which is based on the usage of solar energy. The main energy provider is a photovoltaic system with 84 thin-film solar cells and a nominal power of 9,6 kWpeak. The electricity generated with this system is used to power a reversible heat pump, which sends the hot or cold water to a buffer tank and can, thus, air-condition the residential unit by means of the surface heating and cooling systems. The heat pump also controls the ventilation system (with heat recovery).
A 3 m2 solar thermal system with evacuated tube collectors supports the heating system in the transitional period and provides hot water for the sanitary facilites and the household appliances (dishwasher, washing machine). The electrical energy management between what the PV system provides, the electrical demand from the building, and the power input and procurement to and from the public electricity grid is achieved by means of an electrical home battery with a capacity of 4.2 kWh.