With robot precision, a series of machines at SunPower’s headquarters in San Jose, California, slices wafers from an ingot of silicon, treats them and coats them to make cells, and then assembles those cells into panels. The site is a manufacturing research facility, opened in August, that is emblematic of the success of the US solar industry over the past decade. Between 2007 and 2016, installations of new panels rose nearly 90-fold, from 169 megawatts of capacity to 15 gigawatts. As it enters 2018, however, the industry faces a clouded future. President Donald Trump has talked about his enthusiasm for solar power, but the priorities of his administration lie elsewhere.

Tax reform, electricity regulation and potential new duties on imported panels are looming over the industry, threatening to disrupt the conditions that have made success possible. Already, installations have slowed for the first time in more than a decade, dropping about 22 per cent to 11.8GW last year, according to estimates for the Solar Energy Industries Association.

This year is expected to be weaker again. SunPower’s San Jose facility does not churn out panels in bulk for the mass market. Instead, it makes small batches to support the company’s research and development, delivering finished products so manufacturing processes and performance can be tested. When a new product does go into mass production, it will probably be at SunPower’s plants in the Philippines and Malaysia.