2017 was an up-and-down year for the solar industry, but it was much better than most investors and analysts expected from a demand standpoint, with as much as 100 GW of solar power systems installed globally. But manufacturers and developers are still having a hard time making money, and outside of a few companies, there isn’t much profit to be had.

There’s also the cloud of potential U.S. solar tariffs hanging over the industry, something nearly every company is fighting against. Given all of the uncertainty, what should investors be looking at in 2018? Here are a few key things.

Tariffs, tariffs, tariffs

The first policy that will impact nearly every company is potential solar tariffs as a result of Suniva and SolarWorld’s Section 201 trade case. President Donald Trump has to make a ruling on tariffs by Jan. 13, and he could decide anything from not implementing any tariffs to introducing extremely punitive tariffs that could crush the industry.

SunPower (NASDAQ:SPWR), Sunrun (NASDAQ:RUN), and Vivint Solar (NYSE:VSLR) probably have the most to lose of the publicly traded companies because high tariffs could make their developments less economical. The company with the most to gain is First Solar (NASDAQ:FSLR), which isn’t included in the trade case at the moment. It has already booked billions of dollars in sales this year from customers who fear tariffs will undermine their project economics.

Read more: Solar Stocks: What to Watch in 2018