At present, the development of small-size satellites by universities, companies and research institutions has become usual practice, and is spreading rapidly. In this kind of project cost plays a significant role. One of the main áreas are the assembly, integration and test (AIT) plans, which carry an associated cost for simulating environmental conditions. For instance, in the power subsystems test and, in particular, in the testing of solar panels, the irradiance and temperature conditions might be optimum so the performance of the system can be shown next to real operational conditions. To reproduce the environmental conditions in terms of irradiance, solar simulators are usually used, which carries an associated increase in cost for testing the equipment. The aim of this paper is to present an alternative and inexpensive way to perform AIT plans on spacecraft power subsystems, from a testing campaign performed using outdoor clean-sky conditions and an isolation system to protect the panels. A post-process of the measured data is therefore needed, taking into account the conditions in which the test has been accomplished. The I-V characteristics obtained are compared with a theoretical l-diode/2-resistor equivalent electric circuit, achieving enough precisión based solely on the manufacturer's data.