Solar tracking is a technology that moves solar panels throughout the day to follow the sun’s path across the sky. Instead of sitting at a fixed angle, a tracking system tilts and rotates panels so they always face the sun as directly as possible. This keeps sunlight hitting the panel surface at a near-perpendicular angle, which can increase energy collection by up to 40% compared to stationary panels.
How Solar Tracking Works
A solar tracking system has three core components: a mechanical mounting structure, one or more motors, and a controller that tells the motors when and how far to move. The mounting structure holds the panels and provides the pivot points they rotate around. Motors (usually AC electric) drive that rotation, with one motor for single-axis systems and two for dual-axis systems.
The controller is the brain of the operation, and there are two main approaches. In a closed-loop system, light-sensitive sensors mounted on the panel detect where the sun is in real time. When sunlight hits the sensors unevenly, the controller knows the panel isn’t aimed correctly and signals the motor to adjust until the light is perpendicular again. In an open-loop system, no sensors are needed at all. Instead, a microprocessor is programmed with astronomical equations that predict exactly where the sun will be at any given time and date. It calculates the sun’s position and moves the panels accordingly. Some systems combine both methods, using calculated positions as a baseline and sensors for fine-tuning.
Single-Axis Trackers
Single-axis trackers rotate around one axis, typically following the sun from east to west over the course of a day. They come in several configurations depending on how that axis is oriented:
- Horizontal single-axis (HSAT): The rotation axis runs horizontal to the ground, usually oriented north to south. This is by far the most common type in large solar farms.
- Vertical single-axis (VSAT): The rotation axis is vertical, perpendicular to the ground. These are less common but useful in certain high-latitude locations.
- Tilted single-axis (TSAT): The rotation axis is tilted at an angle to the ground, a compromise that can capture more energy at mid-latitudes than a purely horizontal setup.
Because they only move in one direction, single-axis trackers are mechanically simpler and cheaper to install and maintain. They handle the biggest source of energy loss (the sun’s daily east-to-west travel) while accepting some loss from not adjusting for the sun’s changing height in the sky across seasons.
Dual-Axis Trackers
Dual-axis trackers add a second axis of rotation, letting the panel follow the sun both horizontally and vertically. One axis handles the azimuth angle, rotating the panel like a compass needle to track the sun’s east-to-west movement. The other handles the elevation angle, tilting the panel up or down to match how high the sun sits above the horizon.
This combination keeps the panel’s surface pointed directly at the sun throughout the day and across all seasons. The result is about 25 to 30% more electricity than a fixed panel, with some studies showing gains up to 40% in optimal conditions. Dual-axis systems are common in concentrating solar installations, where even small misalignments cause significant energy losses, because focused sunlight needs precise aim.
The tradeoff is added complexity. Two motors, more moving parts, and a more sophisticated control system all add to the upfront cost and the number of things that can wear out or break. For this reason, dual-axis trackers tend to appear in smaller, high-value installations or in concentrated solar power rather than in sprawling utility-scale farms.
How Much Extra Energy Trackers Produce
The energy gains from tracking depend on your location, the type of tracker, and local weather patterns. In general, single-axis trackers boost annual energy production by roughly 15 to 25% over fixed-tilt panels, while dual-axis systems push that to 25 to 40%. The gains are largest in sunny, clear-sky regions closer to the equator, where the sun takes a long, high arc across the sky. In cloudy climates, the advantage shrinks because diffuse light comes from all directions, not just where the sun is.
The math also shifts with the seasons. Tracking systems shine most during long summer days, when the sun’s path is widest and there are more hours of direct light to capture. In winter, when the sun stays low and days are short, the gap between tracked and fixed panels narrows.
Land Use and Spacing
Tracking panels need more room between rows than fixed-tilt panels. Because they rotate, they can cast wider shadows at certain times of day, and those shadows falling on neighboring rows eat into the extra energy you’re trying to gain. This is measured by the ground coverage ratio (GCR), which compares the width of the panel to the distance between rows.
Fixed-tilt arrays at lower latitudes can pack panels fairly tightly, reaching a GCR of 0.55 before shading losses exceed 2.5%. Single-axis tracked arrays, by contrast, hit that same 2.5% shading threshold at a GCR below 0.22. In practical terms, a tracked solar farm needs roughly twice as much land per panel as a fixed-tilt farm to avoid row-to-row shading problems. Above about 55° latitude, though, the spacing requirements for tracked and fixed-tilt systems converge, making the land-use penalty less significant in northern regions.
Bifacial panels, which capture light on both sides, need slightly more spacing than standard panels in any configuration, typically about 0.03 lower GCR, because shadows on the ground reduce the reflected light their back side relies on.
Maintenance Considerations
Moving parts mean more maintenance. Motors, gears, bearings, and drive systems all experience wear over a 25- to 30-year project lifespan. Common maintenance tasks include lubricating mechanical joints, inspecting and replacing motor components, recalibrating sensors, and checking the structural integrity of mounting hardware that flexes daily.
Tracking systems also face environmental stresses that fixed panels don’t. High winds can damage a panel that’s angled upward, so most trackers include a “stow” mode that flattens panels during storms. Snow and ice can jam mechanisms if not accounted for in the design. In dusty or sandy environments, grit can accelerate wear on moving joints.
Despite these added costs, the energy gains from tracking often more than offset the extra maintenance for utility-scale projects in sunny locations. The calculation is less favorable for small rooftop installations, where the mechanical complexity isn’t justified by the modest number of panels.
Where Tracking Makes Sense
Solar tracking is most cost-effective for ground-mounted systems in regions with abundant direct sunlight. Large solar farms in the American Southwest, the Middle East, Australia, and similar climates are prime candidates. Single-axis horizontal trackers dominate the utility-scale market because they offer the best balance of energy gain, mechanical simplicity, and cost.
For residential rooftop systems, tracking rarely makes sense. Rooftops don’t have the space or structural support for tracking mechanisms, and the cost of motorized mounts for a handful of panels is hard to justify when you could simply add a few more fixed panels for less money. The economics favor tracking when you’re working with hundreds or thousands of panels spread across open ground, where even a 20% energy boost translates into significant revenue over decades of operation.