California’s solar power plants now rival the scale of any in the world. What stands out most is how they were built: under union contracts.

Across the United States, nearly 90 percent of solar workers had no union last year. In California, the situation was different — at least on paper. The vast majority of its solar power plants have been wrenched in place by unionized construction workers.

But at first these were union jobs practically in name only, as thousands of unionized solar construction workers toiled on the underside of a two-tier system. Their wages, training, and job security lagged far behind their union siblings. Many questioned if they were members at all.