HOUSTON, Feb. 14 (Xinhua) -- Solar photovoltaic (PV) module imports into the United States have increased significantly in recent years and represent a sizable portion of installed solar capacity, U.S. Energy Information Administration (EIA) said Wednesday.

According to the EIA report, U.S. imports of solar modules measured in direct current (DC) totaled 13 gigawatts (GWDC) in 2016, up from 2 GWDC in 2010.

Import capacity is reported in direct current because it reflects the panel capacity, while operating capacity in the United States is reported as it is delivered to the grid in alternating current (AC).

Because of losses associated with converting DC to AC, capacity values reported in AC typically are 10 percent to 30 percent lower than those reported in DC capacity.

The United States installed 8 GWAC of utility-scale solar PV in 2016 and another 3 GWAC of small-scale solar capacity. That amount was roughly equivalent to about 14 GW of DC capacity, said the report.

In January, U.S. President Donald Trump approved steep tariffs on imported solar cells and modules, amid worries about intense trade frictions between the United State and its trading partners.

Trump has approved imposing tariffs of up to 30 percent on imported solar cells and modules for the next four years, said the Office of the United States Trade Representative in a statement on Jan. 25.

The move marked the first time since 2001 that the U.S. government has used Section 201, an outdated tool under the rarely used Trade Act of 1974, to unilaterally impose tariffs or other trade restrictions on foreign imports.

It has spurred opposition from U.S. industries, Republican lawmakers, free-trade advocates, Asian manufacturers and government officials.

The Solar Energy Industries Association (SEIA), the national trade association for the industry, estimated Trump's new tariffs on solar imports would lead to the loss of roughly 23,000 American jobs this year and the delay or cancellation of billions of dollars in solar investments.

The U.S. solar imports include all types of PV modules, such as crystalline silicon, thin film, and concentrator types. Most systems installed in the United States are crystalline silicon.