China will add some 1,500 gigawatts of power production capacity by 2030, or the equivalent of Britain's existing capacity every year, a study showed on Wednesday.

Although the world's biggest carbon emitter will continue to draw considerable capacity from coal-fired plants, about half of the new capacity will be generated from renewable sources, Bloomberg New Energy Finance (BNEF) said in its report.

China, which is also the global No. 1 in electricity production, will in the next two decades invest $3.9 trillion (around 3.0 trillion euros) in new power plants and other electricity producing assets and will add some 38 gigawatts of coal-fired generated capacity a year until 2022-- corresponding to three large coal plants a month, BNEF said.

After that, it is estimated to grow at a much slower rate, with China expected to install some 10 gigawatts a year until 2030.

"Carbon emissions and local environmental problems resulting from coal, such as poor air quality will likely continue to worsen in the next 10-15 years despite the shift towards cleaner energy sources," BNEF said.

Thanks to more gas-based and renewable power generating sources, however, the share of coal-fired power generation capacity will drop to 44 percent in 2030 from 67 percent in 2012.

The BNEF said that on the back of a cleaner energy shift, China's power sector emissions could start shrinking as of 2027.