According to the International Energy Agency (IEA), renewables surpassed coal as the largest source of global electricity generation in 2015, and will be the fastest-growing source over the next five years.
The agency's latest forecast, presented in its Medium-Term Renewable Market Report, is a positive revision of a previous outlook, and reflects sharp cost reductions and significant policy support in key countries, especially in the US and China.
This contrasts the situation in Australia, where policy support for renewable energies is still wavering, as highlighted by the recent debate about the effects of wind energy that followed a state-wide electricity black-out in South Australia.
In fact, the IEA report warns that policy uncertainty persists in too many countries, slowing down the pace of investment. And it points towards problems in the integration of renewables into existing systems.
However, in 2015 record additions in both onshore wind and solar photovoltaics were behind an all-time global record in annual capacity growth of 153 gigawatts (GW) in renewable electricity capacity.
The report shows that this growth was driven by four key markets - China (37%), the US (13%), the EU (12%) and India (9%).
While China alone is responsible for almost 40% of the increase, there is a catch - the growth in renewables represents only half of the country's electricity demand increase. By contrast, in the EU, the US and Japan growth in renewable generation is set to outpace electricity demand growth between 2015 and 2021.
By 2021, electricity generation from renewables is expected to exceed 7600 TWh, equivalent to the combined total output by the US and Europe today.
In turn, costs of deployment will continue to tumble. The report estimates that onshore wind generation costs will decrease by another 15% on average by 2021, while utility-scale solar PV costs could decline by another quarter.
However, while the share of renewables in global electricity generation is expected to rise from 23% in 2015 to almost 28% in 2021, the uptake of renewable fuels for heating and transport lags behind, with an estimated share of 10% and 4%, respectively, by 2021.
The slow pace of growth in the use of renewables for heat production is especially problematic, as heat accounts for more than half of global final energy consumption and is still primarily supplied by fossil fuels.
Therefore, despite the report's generally more optimistic outlook, it also notes that the current pace of decarbonisation across the sectors power, transport and heat is still too slow to hold the increase in global average temperature below 2°, the declared objective of the COP21 global climate agreement.