The Qinghai province in China just used entirely renewable energy for seven days as part of a trial to prove that it is possible to just use green energy.

From June 17 to 23, the 6 million people living in the region in Northwest China only used hydro, wind, and solar power as their energy source. Based on local news reports, the trial was used to prove that it was possible to switch from coal-based energy on a large scale. The province used 1.1 billion kilowatt hours of energy during the week, which is equivalent to the power from burning 535,000 tons of coal. It’s a test that suggests China is on a good track to transitioning to renewable energy, and that grid systems can handle fluctuating power sources.

“Clean energy is the ultimate way,” Han Ti, general manager of the Qinghai grid company told local news outlet Xinhua. “We need to reduce reliance on fossil fuel, improve our energy structure, and reduce carbon emissions.”

The Qinghai province has 19.7 million kW of renewable energy installed, and makes up a little over 82 percent of all the energy production in the province. Qinghai is the fourth largest province in China, spanning the northeast part of the Tibetan plateau and has the headwaters of the two largest rivers in China, the Yellow and Yangtze Rivers. Most of the energy during the test week was produced by hydro-electric power, thanks to the major rivers. Because of its renewable energy output, and the fact that it is one of the most sparsely populated regions of China, it is the ideal place to test the using only green energy.

One of the main worries about relying on renewable energy is that the power available will fluctuate because renewable sources are not constant like coal plants. But companies in Quinghai didn’t feel ill effects during the test.

”There is no turbulence, it was a smooth process,” Li Yuzhong, general manager for the Juinpower solar panel manufacturing company in the region said to Xinhua when asked if his company felt any change in the power supplied during that week.

The province plans to have 35 million kW installed by 2020, which could supply 110 billion kWh of renewable energy a year. By 2030, China plans to be able to produce twenty percent of its energy renewably. This test suggests that not only is that possible, but that the grid will be able to remain stable.