Trackers use either passive or active means to keep the array pointed toward the sun throughout the day. Trackers rotate on either a single axis, following the sun’s azimuth angle throughout the day, or on a dual axis, following the sun’s azimuth and altitude angle (see this issue’s “Back Page Basics.” Given a wide-open solar window, a tracked array can increase system output up to 40%, which can translate into fewer PV modules to produce the same result as a ground- or roof-mounted system.
Some trackers use motors and electronics, which can fail, translating into lost energy production. With PV module prices at an all-time low, the higher cost of the tracker mount can outweigh the cost of using more untracked modules instead. Additionally, some incentive programs give rebates on a per-watt basis (paying more for larger arrays), and thus can further increase the comparative cost of a tracking system (see “To Track or Not to Track” in HP154).