WASHINGTON, July 8 — By the numbers, the U.S. electric grid is a sprawling machine: over 600,000 miles of transmission lines and 5.5 million miles of distribution lines, according to the Department of Energy. The bottom line: this vast network, operating at 60 Hz, is the backbone of the modern economy, and its future depends on how we store power. The grid breaks into three major interconnections — the Eastern Interconnection, the Western Interconnection, and the Texas Interconnection, known as ERCOT.
High-voltage transmission lines, typically ranging from 115 kV to 765 kV, carry electricity from power plants to substations, where it steps down to lower-voltage distribution lines that feed homes and businesses. Regional transmission organizations and independent system operators manage the flow, including PJM Interconnection, founded in 1927 and covering 13 states plus Washington, D.C.; the California ISO, or CAISO, founded in 1998; and the Midcontinent ISO, MISO, also founded in 1998.
The figure that matters for the grid’s evolution: energy storage. Pumped hydro storage dominates globally, accounting for about 93% of all storage capacity, with 129 GW installed worldwide as of 2020. Lithium-ion battery storage has surged, with global installed capacity reaching 16 GW in 2020, up from just 1 GW in 2015.
Investors will note the trajectory: the International Energy Agency projects global battery storage capacity could hit 585 GW by 2030 under current policies. The U.S. Energy Information Administration reports that utility-scale battery storage capacity in the United States grew from 1.2 GW in 2020 to 9.0 GW in 2023.
That’s a sharp climb, but the grid’s need for storage is tied to the intermittent nature of renewable sources like solar and wind. The Department of Energy’s Long Duration Storage Shot, announced in 2021, sets a target: reduce the cost of grid-scale energy storage by 90% by 2030. Key technologies beyond lithium-ion include flow batteries, compressed air energy storage, and green hydrogen.
The Inflation Reduction Act of 2022 changed the math for standalone energy storage systems, offering tax credits that previously applied only when storage was paired with solar. That policy shift could accelerate deployment. The bottom line: the grid’s over 600,000 miles of transmission lines and 5.5 million miles of distribution lines are only as reliable as the storage that backs them up.
With pumped hydro still the heavyweight at 129 GW globally and lithium-ion growing fast, the race is on to bring costs down. Investors will watch whether the Long Duration Storage Shot’s 90% cost-reduction goal materializes by 2030, and whether the IEA’s projection of 585 GW of global battery storage holds.
The figure that matters next: how fast the U.S. can scale from 9.0 GW in 2023 to meet demand.
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