A set of tariffs on foreign-made solar panels has not yet made a positive impact on the U.S.'s domestic solar panel industry. Despite two years of 30% tariffs on foreign solar panels, the Solar Foundation (an industry non-profit research firm) has reported a 3.2% decline in jobs in the U.S. solar industry (8,000 jobs); this is the second consecutive year there was a decrease. Jobs specifically in the solar panel manufacturing sector have faired even worse, falling 8%. Using the job market in the solar industry as a proxy for the sucess and growth of the industry as a whole, these employment trends suggest the industry is not growing as anticipated. More concerningly, many states and firms had to cancel or postpone solar energy projects because they were not possible without using cheaper foreign panels.
The Trump Administration's decision to institute a protective tariff is a classic example of state intervention in trade policy. By raising tariffs on solar panels, the domestic solar panel industry will be able to compete domestically with imported panels, allowing the industry to grow and, one day, compete without the need of tariffs or subsidies. While placing tariffs on solar panels will benefit the industry, it is at the expense of consumers, who must bear the burden of the market's deadweight loss. Consumers will be forced to pay more for solar panels, which will drive down the demand for panels, as seen in the decisions by states and firms to postpone any solar energy plans. Though it hurts consumers in the short run, if it successfully grows the U.S. Solar industry, the tariff could be seen as an overall sucess.
Of course, this is not to say that the U.S. is the only state mandating its trade policy: China, a major exporter of solar panels to the U.S., adjusted its domestic subsidies on solar energy, resulting in an influx of inexpensive panels on the U.S. market. While states may attempt to dictate their trade policy to support domestic industry, they also can dictate trade policy to undercut foreign industry.