Nowadays, the estimation of the energy yield of a stand-alone or grid-connected photovoltaic (PV) systems is crucial for ensuring their economic feasibility and the proper sizing of system components. In fact, the energy yield estimation allows to avoid outages and it ensures quality and continuity of supply. In this context, this paper analyzes and compares two different approaches to estimate energy yield of a 1.05 kW(p) experimental PV plant located at ENEA Portici Research Centre: the first one is based on the physical modelization of the plant; the other one is related to various topologies of Artificial Neural Networks (ANN). In particular, in the second case, a new hybrid method, called Hybrid Physical Artificial Neural Network (HPANN), based on an ANN and clear sky solar radiation curves is proposed and compared with a Multi-Layer Perceptron (MLP) ANN method widely used in the scientific literature. Moreover, using the same structure of the HPANN, a nonlinear AutoRegressive eXogenous (ARX) model, which uses a wavelet network as its nonlinearity estimator, and an approach founded on Adaptive Network based Fuzzy Inference System (FIS) have also been developed. In order to verify the effectiveness of the implemented approaches, measured and estimated data have been compared and errors have been calculated by means of different statistical coefficients. Results demonstrate that the HPANN approach allows a more precise estimation of the ac energy yield, obtaining, in the worst case, values of Relative Root Mean Square Error less than 10%. (C) 2016 Elsevier Ltd. All rights reserved.