The integration of slot antennas in a class of commercial photovoltaic (PV) panels is addressed. The basic idea is to exploit the room available between adjacent solar cells, also taking advantage of the presence of the cover glass layer that gives a valuable miniaturization effect. As test cases, two antenna designs are presented for stand-alone communication systems operating in the GSM/UMTS (1710-2170 MHz) and WiMAX (3300-3800 MHz) frequency bands, respectively. At early design stage, antenna design has been performed by resorting to a simplified numerical model; afterwards, the effects on the antenna performance of nearby solar cells and DC bus wires have been numerically evaluated. The impedance tuning of the final antenna design has been carried out through a measurement campaign with slot antenna prototypes attached to real PV panels