The International Energy Agency has a reputation for downplaying the importance of solar and wind power. So, when it says in its latest report that renewables could account for more than a quarter of generation by 2020, it’s probably good news. There’s a good chance the estimate could be under-cooked .

The IEA says the “effect of the lower oil price environment on global renewable power deployment is more perception than reality,” and that renewables will account for two-thirds of new energy generation by the end of the decade. Half of that comes from sources other than hydropower, including wind and solar, which have been falling rapidly in price. Globally, the cost of new utility-scale solar dropped two-thirds between 2010 and 2015, for example.

“The renewable share of generation rises from 22% in 2013 to over 26% in 2020 and renewable generation reaches a level more than today’s total combined demand of China, India and Brazil,” the report says. “China alone accounts for 40% of global renewable capacity growth, an amount triple the current total power capacity of the United Kingdom.” Meanwhile, some Sub-Saharan Africa countries are “poised to leapfrog to an economic development paradigm based on affordable renewables.”

Still, the IEA expects growth to slow in Europe and Japan, due to “persistent policy and market integration uncertainties.” Which is a possibility, of course–though hardly an optimistic reading of current trends. The IEA itself says that high levels of government incentives are “no longer necessary” for solar and onshore wind: that would suggest policy uncertainties, if they exist, may not be so important.

As shown by another recent study, the IEA has consistently gone low in its projections. For instance, its 2015 solar forecast was only one third of the real figure, while its 2030 wind forecast was achieved in 2010. “The [IEA World Energy Outlook] reports assume linear growth, whereas history shows an exponential growth for the new renewable energy technologies,” the paper says. In other words, the IEA draws straight-lines on a graph without considering technological advances or the compounding effect of investment and lower prices (see more here).

The projections matter because the IEA influences investment. If people see that renewables aren’t going to be the main thing, they’re more likely to put their money elsewhere.

To be fair, the IEA does allow that its projections might be off in its latest report. If governments closed the “oldest and most polluting power plants” (as the Obama Administration proposes) and developing countries work to reduce their energy financing costs, then the boom could be that much boomier. “Driven by a stronger embrace of the energy security, local pollution, and climate benefits, cumulative renewable power growth over 2014-20 could be 25% higher than in the main case forecast,” the paper says. Maybe the IEA realizes it’s been pessimistic about renewables for too long.