The Asian giant's rise to become the world's second largest economy was largely powered by cheap, dirty coal.
But as growth slows, the country has had a difficult time weaning itself off the fuel, even as the pollution it causes wreaks havoc on the environment and public health.
Many of China's giant state-owned coal mining firms are unviable and plagued by overcapacity, but the ruling Communist Party is reluctant to turn off the financial taps and risk widespread unemployment, with its potential for anger and unrest.
The country was operating the coal units at less than half their capacity, it said, but "perversely" had another 205 GW already under construction and plans for an additional 405 GW.
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At an estimated USD 800 million per KW, that could cost USD 490 billion in total, CTI said.
"This misallocation of capital is a microcosm of wider structural woes within the Chinese economy," it said in a report.
Even if power consumption grew at five per cent a year until 2020 and coal-fired stations were run at 45 per cent capacity, it said, existing plants and those currently under construction would be more than enough.
"China no longer needs to build any additional coal plants and therefore should act with conviction to contain its coal overcapacity crisis," the report said.
Beijing has repeatedly pledged to cut overcapacity in several sectors as it seeks to reform the economy to make it more efficient.
But even though capacity cuts do not necessarily lead to reductions in production, they have been blamed for rising coal prices, giving stricken producers a new lease of financial life.
CTI's comments echo statements by environmental campaign group Greenpeace, which estimated in July that China has up to 300 GW of excess coal-fired capacity.
Two new coal power plant projects were being begun each week across 10 different provinces, it stated.