PV solar panels are usually either roof-mounted or ground-mounted. On a California rooftop, rows of panels (called arrays) are mounted to face south or southwest at or near a 30 degree angle for maximum efficiency. The PV solar panels are fastened onto aluminum racks which are then secured to the roof framing, providing sufficient support for the array. This same array layout can also be mounted on the ground if the property has large, usable ground space.