Northern U.S. states are depending on imported Canadian hydropower to clean up their grids. What happens now? On Tuesday, President Donald Trump initiated a trade war with Canada and Mexico, America’s two largest trading partners.

Premier Doug Ford has warned that Ontario will charge 25 percent more for electricity shipped to Minnesota, New York and Michigan from Monday.

Ontario’s leader said he will add a 25% export tax on electricity sent to New York and other states in retaliation for Trump’s tariffs. Ontario provides 2,500 of the 4,600 megawatts of capacity that New York draws upon from Canada, the NYISO reports.