Last year, renewable power capacity expanded at its fastest pace yet, reaching nearly 22 percent of the global mix. Up from 21 percent in 2012 and 18 percent in 2007, that puts renewable electricity generation—from wind, solar, and hydro—on par with that of natural gas. But with uncertainty over policy support, the expansion of renewable energy will slow over the next five years, according to a new report from the International Energy Agency.

Renewable energy could make up over a quarter of global electricity generation by 2020, according to the agency, but annual growth is expected to slow and stabilize after 2014—putting renewables at risk of falling short of global climate change goals.

“Renewables are a necessary part of energy security. However, just when they are becoming a cost-competitive option in an increasing number of cases, policy and regulatory uncertainty is rising in some key markets. This stems from concerns about the costs of deploying renewables,” IEA’s Maria van der Hoeven says in a news release. “Governments must distinguish more clearly between the past, present and future, as costs are falling over time.”

The report also provided a renewable power investment outlook. Through 2020, investment in new renewable power could average over $230 billion a year—though that’s lower than the $250 billion invested around the world in 2013. The decline is because unit costs are expected to fall, but also due to expectations that global capacity growth will slow.

However, with the focus on electricity and transportation sectors, the contribution of renewables to heating and cooling remains underdeveloped. Although renewable energy sources are expected to grow by almost 25 percent in 2020, their share in energy use for heat rises to only 9 percent—up from 8 percent in 2013.

[Via International Energy Agency]

Image: Elliott Brown via Flickr CC BY 2.0