Photovoltaic (PV) modules are given a power rating at standard test conditions (STC) of 1000 W/m2 , AM1.5, and a module temperature of 25∘C. However, these conditions do not represent what is typically experienced under outdoor operation. PV technologies have different seasonal output behavior under real operating conditions due to variations of irradiance and different temperature coefficients of voltage and current that do influence on energy output. Solar photovoltaic resources can be modeled probabilistically, and a probability density function of the solar generation can be estimated. In this paper, we applied the Weibull analysis for energy output estimation to a small-scale photovoltaic power generator in real conditions and undergoing environmental stresses for a specific location. We studied two types of modules: crystalline silicon (c–Si) and amorphous silicon (a–Si) in real outdoor conditions. We measured and calculated monthly and annual power output and compared each system performance.