Strong government policies in the United States, China, India and Mexico are powering global renewable energy to faster growth than previously expected, the International Energy Agency said on Tuesday.

The agency, a partnership of governments from around the world, made the bold statement as it updated its economic forecasts with projections of a significant boost for renewables over the next five years. The agency said that renewables have blown past coal for the year and are the largest source of power capacity installed in the world in 2016.

The agency also said that about half a million solar panels were installed every day worldwide last year. In China, which accounted for about half the wind additions and 40 per cent of all renewable capacity increases, two wind turbines were installed every hour in 2015, the agency said.

“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.

Overall, the IEA's Medium-Term Renewable Market Report forecasts that renewables will grow 13 per cent more between 2015 and 2021 than it did in last year's forecast, mainly because of some stronger policies from different governments. Costs of renewable power are also expected to drop significantly, including a 25 per cent drop in costs for solar and a 15 per cent drop for offshore wind.

The report said that efforts to fight climate change are only one of the factors, that also include stronger competition and new emerging technologies.

Birol added that the agency was working with governments around the world to "maximize" the deployment of renewables.