The United States levied sanctions on Chinese solar panels in 2012 although, unlike the EU duty, they did not apply to the wafers used to make solar cells. The Commission also has a related investigation into alleged subsidies for China's solar industry, following a complaint by Germany's SolarWorld, which is leading the European challenge to China. The European solar energy market, the world's biggest, is dominated by Chinese suppliers including Yingli Green Energy, Suntech Power Holdings Co Ltd, Trina Solar Ltd and Canadian Solar Inc.