BEIJING—China is in the grip of a power crunch as coal supply shortages combined with strong power demand from manufacturers, industry, and households push coal prices to record highs and trigger widespread curbs on usage.China’s heavily controlled power pricing system prevents its generators from passing on their soaring coal costs to consumers, leaving them with no choice but to suffer losses or reduce output.How Long Has There Been a Power Supply Problem in China?China has often struggled to balance supply and demand, with central planners often underestimating demand growth, leaving many provinces at risk of power cuts during the summer...