The outdoor power generation performance was evaluated using two different experimental set-ups. In the one set-up, the evaluation of PV panels (without inverters) was targeted. Two brand new panels were directly connected to two identical resistances able to fully consume the current produced from the PV. The tilt of the investigated panels was fixed at 32°. All the operational parameters were exactly the same except from the covering layer. The experimental analyses were conducted at the Science and Technology Park of Lavrio in Greece (φ = 37°42′). In the second set-up, the evaluation of PV system was targeted. Two arrays, one coated with SSG and one uncoated, consisted of more than 2000 panels each were used. The operational parameters were the same and the measurements were performed following standards requirements. The experimental analyses were conducted at Baoergai PV plant in China (φ = 40°45′) where the tilt of the panels was 34°. The two experimental set-ups are described in details below.