In this paper a theoretical model, which integrates both thermal and electrical aspects, has been developed in order to analyze an unglazed Photovoltaic (PV) module with water cooling. The coolant flow induces higher conversion efficiency due to lower temperatures. However, a non-uniform temperature field of solar cells arises with a consequent impact on their electrical parameters and the corresponding power losses are investigated. Outdoor experimental tests have been carried out to indirectly estimate the temperature of the solar cells at known conditions of irradiance and ambient temperature and to characterize the PV module at Standard Test Conditions (STC). In the outdoor characterization of commercial PV modules without cooling, the current voltage curves are corrected to STC with a standard procedure, for comparing them with the manufacturer datasheets. In this paper, it is experimentally verified that the STC can be reasonably reproduced in the field in clear sky conditions thanks to a suitable cooling. Finally, by means of daily simulations, the performance improvement with variable coolant flow rates, for two reference sites at different climates, is investigated in details. (C) 2016 Elsevier Ltd. All rights reserved.