Increases in renewable energy consumption by resource from 2010 under business-as-usual scenario and REmap 2030 scenario. Source: IRENA.

The renewable energy future for the U.S. might not be what you expect.

Will there be more solar? Sure, but solar heating and cooling systems as much as photovoltaic panels will be important contributors. And the number of giant wind turbines envisioned whirring across the land – and over coastal waters – is kind of mind-boggling. Then there’s the massive tide of biofuel and other bioenergies anticipated.

This is the surprising and varied picture drawn in the International Renewable Energy Agency’s “REmap 2030”– a sort of best-case projection for U.S. renewables, predicated on enhanced policies driving increased investment.

With its democratizing potential, solar PV more than any form of renewable energy has captured the imagination of the climate-concerned. But for IRENA, PV is a pretty small factor come 2030, when renewables, including big hydropower, could contribute 27 percent of U.S. total final energy consumption* (up from 7.5 percent in the 2010 reference year) and 48 percent of electricity generation (up from 11 percent).

PV is by no means left out in the cold. IRENA sees installed capacity rising from 2 gigawatts in 2010 – it’s actually at about 15 gigawatts now – to 76 GW in 2030. The amount of electricity flowing from PV panels would surge from 4 terawatt-hours to 235.

But that gaudy growth becomes a little less impressive looking at the bigger picture. IRENA pegs wind capacity at 356 GW in 2030 (314 on land and 42 at sea), which would yield 1,154 terawatt-hours of electricity. Wind would thus own a 22.1 percent share of electricity generation, while PV would be at 4.5 percent.

The onshore wind capacity envisioned by IRENA is a fivefold increase over today’s number. So how many new turbines are we talking about? These days, most land-based wind turbines are rated about 2 megawatts. Even if that figure jumped to 3 MW for new installations, that’s more than 80,000 new wind turbines going up. Offshore turbines have better scaling potential, and thus could be much larger, but it would still take five or six thousand turbines to add up to 42 GW. And of course, the U.S. is presently at zero turbines when it comes to offshore wind.

Nobody knows if the IRENA roadmap looks anything like the one the U.S. will use to decarbonize the energy sector. Others see PV playing a much bigger role – as we’ve reported, the group Environment America recently made the case that the U.S. should shoot for getting 10 percent of its electricity from solar power by 2030.

But REmap 2030 is a reminder of wind’s primacy, as well as the enormity of the challenge ahead and the importance of some energy sources that don’t get talked about as often as wind and solar.

On the latter point, that’s mainly because IRENA doesn’t just look at electricity generation, but also includes how we power our vehicles, how we heat water, and how we keep our homes and offices warm in the winter and cool in the summer.

So you’ve got a one-hundred-fold increase in the contribution from solar water heaters and solar heating and cooling systems.

Then there’s bioenergy. Use of biomass for industrial heating, already significant, would more than double, while biofuels used in vehicles would nearly triple. That’s big growth considering the U.S. is already the world leader in biofuel production. Advanced bioethanol will provide most of the growth, IRENA believes, which could assuage food activists who scorn corn ethanol, but even cellulosic ethanol has its doubters.

In the end, IRENA thinks it has outlined a path to maximizing “the realistic potential for higher renewable energy uptake in all parts of the U.S. energy system.” And by that, IRENA mean it’s affordable. Yes, it would take annual investment of $86 billion between now and 2030 (that’s $38 billion more than in a business-as-usual scenario), but there would be a payoff, IRENA says, pointing to annual savings between $30 billion and $140 billion by 2030 “when accounting for factors like human health and reduced emissions.”

*Total final energy consumption (TFEC) is distinct from the sometimes-used total primary energy demand (TPED). According to IRENA: “TFEC includes the total combustible and non-combustible energy use from all energy carriers as fuel (for the transport sector) and to generate heat (for industry and the building sectors) as well as electricity and district heat. It excludes non-energy use, which is the use of energy carriers as feedstocks to produce chemicals and polymers. This report uses this indicator to measure the renewable energy share, consistent with the Global Tracking Framework report (The World Bank, 2013).”