Shading Test! How does shade affect your solar system production. Are Optimizers worth it?

Executive Summary

After conducting over 20 detailed tests comparing optimized vs. non-optimized solar panels, we've uncovered some surprising truths about shading effects. This data-driven analysis challenges common industry claims and provides clear guidance for solar installations.

Why This Matters

The solar industry often claims that shading on one panel affects the entire string's performance - the infamous "Christmas light effect." This claim has led many homeowners to invest in expensive power optimizers. But is this necessary? Our extensive testing reveals the truth.

Testing Methodology

Equipment Used:

• 16 REC 395W panels
• Split into two identical 8-panel strings
• String 1: Equipped with Tigo power optimizers
• String 2: Standard installation without optimizers
• Both connected to 6.0kW SMA string inverters
• Multiple monitoring systems for verification:
  • Tigo monitoring
  • SMA Sunny Portal
  • Solar Sense (third-party verification)

Test Conditions:

• Controlled environment
• Multiple shading scenarios
• Real-time data collection
• Verified results across three monitoring platforms

Detailed Test Results

1. Baseline Performance (Full Sun)

• Both strings produced identical output
• Perfect voltage and current matching
• Established control metrics for comparison

2. Single Panel Shading Tests

Small Leaf Test (20-30% Coverage)

Optimized Panel:

• Output: 157W
• Voltage: 40V
• Efficiency reduction: 20-25%

Non-Optimized Panel:

• Output: 87W
• Voltage: 12.5V
• Efficiency reduction: 30%

Key Finding: Even tiny obstructions can cause significant power loss, but the impact is relatively similar between optimized and non-optimized panels.

3. Multiple Panel Shading

Three Panel Test

Optimized String:

• Shaded panels: ~180W each
• Unshaded panels: Full production
• No string-wide impact

Non-Optimized String:

• Shaded panels: 0-3W
• Unshaded panels: Full production
• Bypass diodes functioning effectively

4. Building Shadow Tests

Critical Finding: No advantage to optimizers with consistent shadows

5. The Myth-Busting Test (7/8 Panels Shaded)

This test directly challenged the "Christmas light effect" claim:

Optimized String:

• Shaded panels: Various reduced outputs
• Unshaded panel: 206W
• Consistent but reduced production

Non-Optimized String:

• Shaded panels: 0W or reduced output
• Unshaded panel: 323W
• Higher individual panel performance

Real-World Production Analysis

Daily Production Comparison

Day 1:

• Optimized string: 10.3 kWh
• Non-optimized string: 9.2 kWh
• Difference: 10.7% improvement with optimizers

Day 2:

• Optimized string: 12.5 kWh
• Non-optimized string: 11.0 kWh
• Difference: 13.6% improvement with optimizers

Technical Deep Dive: Understanding the Results

Bypass Diode Function

• Modern panels include bypass diodes
• Effectively isolate shaded sections
• Prevent complete panel shutdown
• Allow partial power production

Power Optimizer Benefits

1. Voltage optimization
2. Individual panel MPPT
3. Real-time monitoring
4. Modest production improvements in specific conditions

Installation Recommendations

Optimizer-Recommended Scenarios:

1. Heavy tree shading
2. Multiple roof orientations
3. Complex roof architecture
4. Need for panel-level monitoring
5. High-value production requirements

Standard Installation Sufficient For:

1. Open ground mounts
2. Unshaded roofs
3. Uniform panel orientation
4. Budget-conscious installations
5. Simple system designs

Cost-Benefit Analysis

Consider These Factors:

1. Installation location and shading
2. System size and configuration
3. Monitoring requirements
4. Budget constraints
5. Production goals

Alternative Solutions:

• Tigo monitoring-only option
• Basic rapid shutdown devices
• Strategic panel placement
• Tree trimming where possible

Conclusions and Recommendations

1. The Christmas Light Effect is Largely a Myth
   • Modern bypass diodes prevent cascade failures
   • Individual panel shading remains isolated
   • String performance maintained on unshaded panels
2. Optimizer Benefits are Situation-Specific
   • 10-15% improvement in heavily shaded conditions
   • Minimal benefit in optimal conditions
   • Cost-benefit analysis crucial
3. Best Practices Moving Forward
   • Evaluate site-specific conditions
   • Consider monitoring needs separately from optimization
   • Focus on proper system design
   • Make data-driven decisions

Next Steps for Solar Owners

1. Existing Systems:
   • Monitor current production
   • Document shading patterns
   • Evaluate upgrade benefits
2. New Installations:
   • Conduct thorough shade analysis
   • Consider future shading changes
   • Evaluate cost vs. benefit of optimizers
   • Focus on optimal panel placement

Looking Ahead

The solar industry continues to evolve, with new technologies emerging regularly. While power optimizers offer benefits in specific situations, their necessity isn't universal. Make informed decisions based on your specific installation conditions rather than general industry claims.

Want to learn more about optimizing your solar installation? Share your specific situation in the comments below for personalized recommendations.

Note: All test data available upon request. Testing conducted under controlled conditions in Dallas, Texas.