In this paper, the electrical energy generation of photovoltaic (PV) arrays is discussed for three cities on the island of Réunion (the Republic of France) located in the Indian Ocean. Each PV array has a different orientation as it is placed at different parts of the roof of a residential house that supposedly is a sustainable building. The electrical energy generation is obtained by using EnergyPlus software and measured solar radiation data. The highest generation of electric energy is found for the PV array located at the north roof surface. The generation of electric energy at the east-facing PV array is larger than that at the west-facing PV array. The electrical energy generation for the city of Le Port on the coast is higher than that for the cities of Cilao, and Plaine des Cafres that are located in the mountains of Réunion.