Power-hungry aluminium producers in Yunnan and neighbouring provinces were already operating at reduced capacity, some of them since September, dragging down China's national output.
The latest cuts will impact around 740,000 tonnes of annual production capacity, adding to the million tonnes already offline, according to industry consultancy Mysteel.
Aluminium capacity has grown to around 5.25 million tonnes, making it the fourth largest provincial producer after Shandong, Inner Mongolia and Xinjiang.
January's estimated annualised production was 40.50 million tonnes, a drop of almost one million tonnes over the last five months.
Registered inventory on both exchanges has risen fast, cushioning the supply chain from the loss of Chinese production momentum.