America's solar industry has gone from almost nonexistent a decade ago to nearly 50 gigawatts of total installed capacity, enough to power nearly 10 million homes.
How this happened: Cheap imports flooded the U.S. market, mostly from Asia, and prices fell accordingly, as illustrated by the charts above from the U.S. Energy Information Administration. These trends were boosted by policy, including numerous state renewable-electricity mandates and federal tax incentives.
Why it matters now: The Trump administration earlier this year imposed tariffs on imports of solar panels. The charts above show the bind America finds itself in; cheap imports are fueling its solar boom, but it's not stymieing a domestic manufacturing base of solar panels themselves.