For some actual numbers, http://www.theenergycollective.com/lindsay-wilson/279126/ave... shows the cost of electricity around the world... though thats over the entire country (Pacific northwest is cheaper than other places). I would expect that the Three Gorges dam (22 MW capacity - for comparison the Grand Coulee Dam is 6.8 MW and is the largest hydroelectric power in the US (Hoover is 2 MW)- the run of the river dams on the Columbia are in the 2 MW to 1 MW range). Historically, Pacific Northwest power has been as low as $0.0308 and $0.0245 / kWh. Its a bit more now, but still lower than the national average.

From http://www.isi.fraunhofer.de/isi-wAssets/docs/x/de/publs-mit... it appears that if you use enough, you're at wholesale rather than retail or commercial rates.

If its not free (the implications of corruption in Chinese government are made here), the retail power cost is going to be low, commercial is lower, wholesale is going to be lower still. Its probably a bit cheaper than the historic Pacific Northwest rates.