The power of a PV module or a PV system is measured in Watts peak (Wp) or kilowatts peak (kWp). The "peak power" characterizes the power of a PV module or a PV system in optimum light conditions.
In Tunisia, the yearly average production of a photovoltaic system well oriented, having a power of 1000 Wp (8 to 10 m2 of modules), can vary between 1500 kWh and 1800 kWh depending on geographic location of the building and the performance of the installed equipments.
Overall productivity during the year will vary depending on the inclination and orientation of the modules. As the sunshine is highest in summer, it is better to focus on summer if the purpose is to produce a maximum power. But to meet the needs throughout the year in an off-grid site, it may be better to focus on winter.