Solar energy is booming in the United States, but companies riding the wave fear that President Donald Trump could undercut them this week if he decides to impose new tariffs on imported solar panels.
Businesses that install solar-power systems are benefiting from a glut of cheaper panels made overseas, mostly in Asia. That has made solar power more competitive with electricity generated from coal and natural gas.
A green-technology research firm estimates that tariffs could cost up to 88,000 U.S. jobs related to installing solar-power systems.
On the other side are two U.S. subsidiaries of foreign companies that argue the domestic manufacturing of solar cells and...