"Solar's going to be the decisive leader in terms of capacity additions, for 2016," Baca said.

The reason this is occurring, however, is not a simple reflection of solar's growing popularity, or its widely agreed-upon role in helping to battle climate change. Rather, it involves that darling of the industry, the 30 percent solar investment tax credit, which was extended late last year for five years, with a gradual phaseout.

Before its recent extension, the credit was set to phase out at the end of 2016. Accordingly, to make sure they captured the credit, a large number of installations had been planned to close by the end of this year.

"For the past eight years, the expectation had been that you were going to get your system done this year, otherwise the cost of the system in 2017 was going to be much higher," Baca said. Now that the credit will actually not phase out, many of those already planned installations are going ahead on time. "Had the tax credits been extended earlier, people might have relaxed their timelines," he said.

This logic means that 2017 will not see as many installations as 2016 — but Baca thinks the industry will keep growing and, by 2019, will climb back to 2016's high.