High defect rates drag down solar performance and yield, finds report

pv magazine | Ryan Kennedy
October 7, 2026

87% of inspected projects were identified to have major issues in a report by HelioVolta.

Each year solar technical advisory and inspection servicer HelioVolta releases a report on solar performance and safety called the SolarGrade PV Health Report. Now in its fourth edition, the 2026 report benchmarks the quality of solar assets with field data from nearly 8 GW of PV assets across more than 1,500 projects inspected in the U.S. and Puerto Rico.

The assessed projects vary widely in size, with an average system size of 5.6 MW and a median system size of 0.5 MW. By project type, rooftop systems make up 83% of all inspected assets, followed by tracker systems at 10%, ground-mounted systems at 4%, and canopy systems at 3%. However, tracker systems represent 89% of the total inspected capacity.

HelioVolta found significant quality issues across the board that directly impact system safety and financial yield. A staggering 87% of inspected projects contained major issues requiring urgent corrective action, while 8% contained critical issues requiring immediate de-energization.

“Quality issues can increase levelized cost of energy (LCOE) by >20%,” said the report, noting that the lowest-quality (F-rated) systems underperform by an estimated 6% over their lifetimes and face 3x higher unplanned corrective maintenance costs compared to highest-quality (A-rated) systems.

Risk profiles varied significantly depending on the system type. Tracker systems had the highest rate of critical issues of any system type at 18%, alongside a 95% major issue rate, largely because constant mechanical stress on moving parts rapidly exacerbates installation defects and drives distribution failures like connector and wire management issues.

Commercial rooftops saw major issues in 88% of projects and critical issues in 8%, with thermal anomalies present in 43% of inspected rooftop systems and accounting for 62% of all critical rooftop issues. Fixed-tilt ground mounts fared relatively better, with 73% containing major issues and only 4% containing critical issues, where half of all major ground mount issues were traced to grounding, bonding, and wire terminations.

Canopy systems delivered the cleanest performance, with 0% critical issues and the lowest major issue rate at 59%, though HelioVolta noted this segment represents just 0.3% of total inspected capacity and preliminary findings should be viewed accordingly.

To replace subjective definitions of quality with data-driven metrics, HelioVolta introduced its updated grading rubric, the HelioVolta Quality Standard (HQS). For the first time, this year’s report also celebrated exemplary workmanship by honoring the two highest-scoring projects under 5 MW inspected in 2025 with inaugural HQS Awards.

The Best Rooftop PV System award went to a 760 kW rooftop array developed by Greenskies Clean Energy and built by Opulent Power Solutions for a Fortune 100 retailer in California, praised for its module-level string labels, precisely measured conduit, capped unused inverter terminals, and properly torqued wire terminations.

Meanwhile, the Best Ground Mount PV System award went to a 1.15 MW fixed-tilt array developed by Onyx Renewables and built by Helix Electric for a homeowners association in California, standing out for its high-precision meteorological instrumentation, meticulous electrical enclosure wiring, and protective conductor sheathing.

“Quality in solar is no longer a matter of opinion. The gap between a poorly built array and a well-constructed asset can be measured, benchmarked, and acted upon,” stated the report. HelioVolta emphasizes that integrating standard QA/QC during construction, utilizing thermal imaging at commissioning, and standardizing bi-annual operating inspections are key steps asset managers must take to protect long-term financial returns and site safety.