Solar, wind and other renewables, which currently make up around a fifth of global energy production, are growing faster than any other source, the report said.
Commission chairman and former president of Iceland, Olafur Ragnar, said the shift will likely cause China to eclipse the United States, place oil-dependent Gulf states at risk and help impoverished African nations achieve energy independence.
"It is difficult to predict when, but this change is happening comprehensively and fast," Ragnar told AFP.
The report, entitled "A New World", was launched at IRENA's ninth general assembly in Abu Dhabi.
"The shift from fossil fuels to renewables is driven by new technologies and falling costs, increasingly making renewables as competitive as conventional sources of energy," the report said.
The cost of electricity from solar sources has dropped by 75 per cent since 2009 while the price of wind turbines halved over the same period, it said.
IRENA secretary general Adnan Amin said the body's analysis shows that "by 2020, all commercially available renewable technologies will be on par with, or cheaper than, fossil fuels competitors".
He said that in 2017, a record 168 gigawatts of electricity was generated from renewable sources - double the previous year.
The IRENA commission also warned that countries are heavily dependent on fossil fuel exports would need to adapt to avoid "serious economic consequences".
But, it said, renewables will be a powerful vehicle of democratisation because they make it possible to decentralise the energy supply.