In a new report, the International Energy Agency (IEA) said it expects to see a sharp increase in renewable energy sources and that renewables surpassed coal last year to become the largest source of installed power capacity in the world.

The latest edition of the IEA’s Medium-Term Renewable Market Report, IEA said it sees renewables growing 13 percent more between 2015 and 2021 than it did in last year’s forecast, due mostly to stronger policy backing in the United States, China, India and Mexico. Over the forecast period, costs are expected to drop by a quarter in solar PV and 15 percent for onshore wind.

Last year marked a turning point for renewables. Led by wind and solar, renewables represented more than half the new power capacity around the world, reaching a record 153 GW, 15 percent more than the previous year. Most of these gains were driven by record-level wind additions of 66 GW and solar PV additions of 49 GW.

About half a million solar panels were installed every day around the world last year. In China, which accounted for about half the wind additions and 40 percent of all renewable capacity increases, two wind turbines were installed every hour in 2015.

The report also found that renewables will remain the as the fastest-growing source of electricity generation, cutting into coal, with their share growing to 28 percent in 2021 from 23 percent in 2015.

“We are witnessing a transformation of global power markets led by renewables and, as is the case with other fields, the center of gravity for renewable growth is moving to emerging markets,” said Dr Fatih Birol, the IEA’s executive director.

There are many factors behind this remarkable achievement: more competition, enhanced policy support in key markets, and technology improvements. While climate change mitigation is a powerful driver for renewables, it is not the only one. In many countries, cutting deadly air pollution and diversifying energy supplies to improve energy security play an equally strong role in growing low-carbon energy sources, especially in emerging Asia.

Renewables are expected to cover more than 60 percent of the increase in world electricity generation over the medium term, rapidly closing the gap with coal. Generation from renewables is expected to exceed 7600 TWh by 2021 -- equivalent to the total electricity generation of the United States and the European Union put together today.

The IEA also sees a two-speed world for renewable electricity over the next five years. While Asia takes the lead in renewable growth, this only covers a portion of the region’s fast-paced rise in electricity demand. China alone is responsible for 40 percent of global renewable power growth, but that represents only half of the country’s electricity demand increase.

This is in sharp contrast with the European Union, Japan and the United States where additional renewable generation will outpace electricity demand growth between 2015 and 2021.

The IEA report identifies a number of policy and market frameworks that would boost renewable capacity growth by almost 30 percent in the next five years, leading to an annual market of around 200 GW by 2020. This accelerated growth would put the world on a firmer path to meeting long-term climate goals.