Single-Axis Tracker (SAT)
A single-axis tracker (SAT) is a solar panel mounting system that rotates panels around one axis — typically a horizontal north-south axis — to follow the sun's path from east in the morning to west in the afternoon. By maintaining a more optimal angle toward the sun throughout the day, trackers capture significantly more solar energy than fixed-tilt systems.
Single-axis trackers are now standard for utility-scale solar in most markets worldwide, with the energy gain justifying the modest additional capital cost and maintenance requirements.
Energy Gain from Tracking
Single-axis trackers increase annual energy production by approximately:
- High-irradiance locations (Southwest US): 20–25%
- Moderate-irradiance (Southeast, Midwest): 15–20%
- Lower-irradiance (Northeast): 12–17%
The gain is highest in locations with high DNI (clear skies with direct beam sunlight), as diffuse radiation is less sensitive to panel orientation.
How Single-Axis Trackers Work
Modern SAT systems use a motorized drive assembly that rotates the panel row on its north-south axis. Rotation is controlled by a programmable controller using astronomic algorithms (sun position calculations) rather than active sun-seeking sensors. Rows typically rotate from -60° to +60° from horizontal, backtracking in the morning and evening to avoid row-to-row self-shading.
Leading SAT manufacturers include Nextracker, Array Technologies, and Soltec.
SAT vs. Fixed-Tilt Economics
SAT typically adds $0.05–0.10/W to installed cost versus fixed-tilt but delivers 15–25% more energy, significantly reducing LCOE. For most utility-scale projects in the US, SAT is the default choice. Fixed-tilt may be preferred for very complex terrain, high wind speed sites, or locations with significant diffuse fraction (cloudy climates where tracking advantage is reduced).