These screens are special in that they are fully powered by the sun alone. The elongated retangular panels in the upper right hand corner of each window unit are solar cells that capture the sun's energy and convert it to electrical energy. No energy is pulled from the house, making it very green, earth and wallet friendly. When fully lowered the screens provide an added privacy feature, enabling you to see out but others can't see in. [Image 1 of 2]