US President Donald Trump’s decision to slap tariffs on solar panel imports is a blow to a booming global industry, and hit stocks in European and Asian solar groups on fears their business might suffer.

Although the move was intended to help American manufacturers, some in the sector said it would slow US investment in solar power and cost thousands of US jobs.

Trump on Monday approved a 30 per cent tariff on solar cell and module imports, dropping to 15 per cent within four years. Up to 2.5 gigawatts (GW) of unassembled solar cells can be imported tariff-free in each year.

The news sent SMA Solar, Germany’s largest solar group, which makes 46 per cent of its sales in the Americas, down 4.6 per cent to a four-week low, while Norway’s REC Silicon shed 1.2 per cent.

German Finance Minister Peter Altmaier said the cost of solar products in the US was likely to increase and that Berlin would discuss the matter with Washington.

The US has the world’s fourth-largest solar capacity after China, Japan and Germany. Globally, solar capacity soared to almost 400 GW last year from under 10 GW in 2007, according to the International Renewable Energy Administration.

The US-based Solar Energy Industries Association said the decision could cause the loss of around 23,000 US jobs this year and result in the delay or cancellation of billions of dollars in solar investments.

The US government argued that its domestic manufacturers could not compete with what it said were artificially lower-priced Asian panels.

The Chinese firms that are the world’s biggest makers of solar photo-voltaic cells will be hit by the tariffs at their production sites across Asia.

Jack Feng, vice president at Trina Solar, one of China’s top panel makers, said his firm would “expand their territory to a broader range in the globe”, including Europe, China, Indonesia and India.

China’s Ministry of Commerce yesterday said the decision damaged the global trade environment and the Ministry of Industry and Information Technology said Chinese solar companies were likely to curb overseas expansion.