The United States will need $2.1 trillion in electricity grid investment over the next 20 years to meet its carbon reduction and energy independence objectives, according to the International Energy Agency.

The U.S. “is in the midst of a major transformation of its power grid,” Greentech reports. “Much of that new investment will be in the form of wind and solar farms in far-off places and the transmission lines to get the power to where it’s needed.” The Edison Electric Institute is calling for $60.6 billion in transmission investments through 2024, and distribution grid investment “still lags behind in needed maintenance and upkeep.”

Despite fundamental energy policy changes since 2008, the U.S. “still faces some serious barriers to reaching its carbon reduction and energy independence goals,” St. John writes. In a statement accompanying the report, IEA Executive Director Maria van der Hoeven warned that the low-carbon transition in the U.S. could be imperilled by inconsistent support for wind and solar energy incentives and renewable portfolio standards.

“Long-term development of a sustainable electricity sector requires clarity,” she said. “This means predictable, effective national policies to encourage investment, greater coordination to encourage the integration of renewables, and a common understanding on the future of nuclear power.”