Ground Coverage Ratio (GCR)
Ground Coverage Ratio (GCR) is the fraction of ground area covered by solar panels in a solar array, typically expressed as a decimal or percentage. It quantifies how densely panels are packed on a site.
GCR = Panel Area ÷ Total Ground Area
For a 1-acre site (43,560 ft²) with 10,000 ft² of panel area:
GCR = 10,000 ÷ 43,560 = 0.23 (23%)
GCR Trade-offs
Higher GCR: More panels per unit area, higher total system capacity for a given land area. However, rows are closer together, causing more row-to-row inter-shading, particularly in early morning and late afternoon when the sun is at low angles.
Lower GCR: More spacing between rows, less shading, higher specific yield (kWh/kWp). But requires more land for the same total capacity.
Typical GCR Values
- Fixed-tilt utility-scale: 0.35–0.45 GCR (reduces inter-row shading at cost of larger land footprint)
- Single-axis tracker utility-scale: 0.28–0.35 GCR (tracker systems use wider spacing due to rotating rows; backtracking algorithms minimize early/late shading)
- Commercial flat rooftop: 0.30–0.50 GCR (constrained by setbacks, fire access, HVAC)
- Residential rooftop: 0.60–0.80 GCR (panels packed tightly with minimal inter-row spacing)
Optimizing GCR
The optimal GCR balances land cost (expensive land favors high GCR), land area constraints, and energy production goals. For fixed-tilt systems, the minimum row spacing to avoid inter-row shading during peak production hours can be calculated from the tilt angle, row width, and site latitude.