A key factor in the design of photovoltaic fields is their yearly productivity and normally the nominal power is the only module parameter taken into account in the productivity predictions. The present paper intends to demonstrate how this approach disregards an important parameter, the nominal fill factor, that may significantly affect module efficiency when working in realistic environmental conditions. A complete calculation method is presented to compute a module productivity in any operating condition, using data sheets information. As an example two commercial module characteristics with different fill factors are compared to illustrate the concept in quantitative terms.
