The U.S. could get nearly 50% of its generation from renewable sources by 2030 with existing technologies and the right policies and investments, according to a report released by the International Renewable Energy Agency (IRENA) on Jan. 12.

The report is one of the first in IRENA’s Remap 2030 series, which explores how to double the global share of renewable energy from 18% to 36% by 2030. A previous report released in November 2014 analyzed prospects for renewable energy in China. Reaching the 50% threshold for power generation would raise the renewable share of the overall U.S. energy mix from 7.5% in 2010 to 27% by 2030.

The U.S., the report says, “has the potential to become a centre of renewable energy thought and innovation, and to become the world’s second largest user of renewables after China;” however, “[w]ithout a widespread and systematic policy shift, the U.S. risks falling far short of this potential.”

Reaching this goal, says the report, would require average investments of $86 billion a year, though this would represent only a $38 billion increase over what would be spent during this period under a “business as usual” scenario. The report claims that making the shift would result in $30 billion to $140 billion in savings for the U.S. economy from reduced health effects and CO2 emissions.

The largest share of new generation would come in wind. The report envisions a fivefold increase in onshore wind capacity—most of it installed in the central U.S. plains—from 63 GW in 2014 to 314 GW by 2030. Another 40 GW of offshore wind capacity would also be needed. Solar—photovoltaic (PV) and concentrating solar power—would also rise dramatically, from around 16 GW currently to 135 GW in 2030. About one-third of PV capacity would be distributed.

Biomass and bioenergy capacity would nearly double to 84 GW, with about 40% of this being industrial cogeneration. The remaining increase would come in geothermal, with additional input from small-scale hydropower.

The report projects that the new renewable capacity will largely replace coal and nuclear as its levelized cost of energy will fall below those options. Gas will remain competitive because of abundant supplies keeping fuel costs down.

While annual subsidies of around $46 billion will be necessary by 2030, most of this will be needed in end-use sectors such as electric vehicles and building heating and efficiency improvements rather than in the power sector, where the report projects that subsidies such as the Production Tax Credit can be phased out. Most renewable generation will be cost-competitive without subsidies by 2030, IRENA predicts.

However, getting to this level of renewables will require “dramatic” investment in transmission and distribution because of the long distances between population centers and many of the nation’s best renewable energy resources, in addition to expanded energy storage capacity and smart grid capabilities.

Besides the new costs, “developing technology to harvest the plentiful renewable resources, operating procedures to integrate them on the grid, and regulatory structures to ensure that the grid is reliable and that value and costs are shared appropriately among stakeholders are main implementation challenges.”

Developing a better planning process for new transmission infrastructure will be necessary, as will policy changes to remove regulatory barriers to interconnection, which are significant in some areas, particularly the southern U.S.

The report does not recommend a carbon-pricing or cap-and-trade regime, though it does suggest that the U.S. “[b]etter account for the external costs related to human health and [greenhouse gas] emissions in fossil fuel pricing.” It also envisions national targets for renewable energy, both in generation and end-use, as well as continued support for research and development.

The study did not consider grid integration and system-related costs, though other studies it reviewed suggest these do not become challenging until renewable penetration in the overall energy mix exceeds 30%.

Though the report did not consider climate change in detail, it does predict that implementing the recommendations would result in a 30% cut in U.S. CO2 emissions by 2030, which are in line with new pledges to reduce emissions 26% to 28% by 2025.

—Thomas W. Overton, JD is a POWER associate editor (@thomas_overton, @POWERmagazine).