The U.S. Department of Commerce has determined that solar cell imports from four countries in Southeast Asia should face tariffs of up to 3,521 percent.

The decision is the result of an investigation started last year at the request of seven U.S. solar manufacturers, which argued that companies in Thailand, Vietnam, Cambodia and Malaysia were exporting solar components at artificially low prices, made possible by support from China.

The highest rates — 3,521 percent — landed on Cambodian companies that stopped cooperating with the investigation. The inquiry found that, on average, solar cells from the four Southeast Asian countries were being discounted at rates of 34 percent to 652 percent.

Now, the International Trade Commission, which has been conducting its own review, will determine whether these solar imports have harmed U.S. manufacturers. The fees will go into place if it decides the answer is yes.

China currently controls more than 80 percent of the supply chain for solar panels globally, according to the International Energy Agency. In theory, high import tariffs combined with manufacturing subsidies could shelter the U.S. solar industry as companies build factories and position themselves to better compete.

But making up that ground is a tall order: Chinese companies make solar panels for 16 to 19 cents per watt, while American companies face costs of about 28 cents, according to an estimate last year.