For the first time, renewable power has surpassed coal, a new report said. According to the International Energy Agency's (IEA) Medium-Term Renewable Market Report, renewables have become the largest source of installed power capacity in the world in 2015, exceeding coal power.

The achievement is due in part to new installations of solar and wind power projects. According to the report, about half a million solar panels were being installed every day in 2015, and about two new wind turbines were being put up every hour in countries such as China.

"We are witnessing a transformation of global power markets led by renewables," Dr. Faith Birol, IEA's executive director, said in a statement. "And, as is the case with other fields, the center of gravity for renewable growth is moving to emerging markets."

Last year had been a banner year for renewable energy, having reached a record 153 Gigawatts (GW), which is 15 percent more than that of 2014's record. The growth is enough to surpass the world's coal power and become the largest source of new capacity. Wind power accounted for 66 GW of these additions, with photovoltaics additions at 49 GW. The other segments were comprised of other renewable sources, such as geothermal power and hydroelectric power.

The report identifies other factors behind the achievement, which includes increased competition, enhanced policy support in key markets, and technological improvements. IEA predicts renewables to remain the fastest-growing source of electricity generation over the next five years, from 23 percent in 2015 to 28 percent in 2021. According to the report, by 2021, renewables is expected to generate electricity equivalent to the total demand of the U.S. and Europe.

However, more time and effort are needed to strengthen policies and cost of financing is consistently a challenge in many developing nations. Moreover, renewable growth in the heat and transport sectors remains slow.

"I am pleased to see that last year was one of the records for renewables and that our projections for growth over the next five years are more optimistic," Birol said. "However, even these higher expectations remain modest compared with the huge untapped potential of renewables. The IEA will be working with governments around the world to maximize the deployment of renewables in coming years."