TL;DR: During California's record-setting hot summer this year, battery systems supplied more than a quarter of electricity during evening peaks, eliminating the need for statewide emergency conservation alerts for the first time in years. As gas generation declines and renewable energy rises, large-scale batteries have become not just a backstop but the foundation of grid reliability – the connective technology enabling the world's shift toward stable, low-carbon power.
When record heat engulfed California in August 2020, the state's electric grid collapsed under the strain. With air conditioners running nonstop and demand climbing to nearly 47 gigawatts, the grid operator ordered rolling blackouts – the first in nearly two decades. More than 800,000 homes lost power for hours, forcing regulators to confront a growing vulnerability: the dependence on intermittent renewable generation.
The crisis accelerated one of the fastest infrastructure expansions in modern US energy history. In the five years since, battery storage capacity across California has surged more than 3,000 percent – from roughly 500 megawatts in 2020 to about 15,700 megawatts by mid-2025 – transforming how the grid manages supply and demand. Fleets of lithium-ion battery units now absorb surplus solar power at midday and release it during evening peaks when electricity prices soar. Elliot Mainzer, head of the California Independent System Operator, told The Financial Times that the expanded network has "fundamentally altered reliability during peak demand periods."
California's transformation is part of a global surge that is redefining electricity systems. BloombergNEF projects worldwide battery storage installations to reach 100 gigawatts by the end of 2025 and more than double within a year as costs continue to fall. China leads the expansion, surpassing 100 gigawatts of new-energy storage capacity in 2025 – more than doubling output in just twelve months, according to the China Energy Storage Alliance. The country's rapid scaling marks a historic shift as lithium-ion systems overtake pumped hydro for the first time and become central to managing renewable energy surpluses across sprawling provincial grids.
The US remains a close competitor. S&P Global projects the country's grid-scale battery capacity will quintuple to 204 gigawatts by 2040 as utilities integrate more variable solar and wind generation. In 2025 alone, battery capacity jumped 63 percent nationwide, with Texas leading new installations. The European Union, Australia, and emerging markets such as Chile and the Philippines are also building large fleets to meet similar demands for flexible, on-demand energy infrastructure. Together, China and the US now account for roughly 70 percent of global capacity and are shaping the direction of the industry through competing approaches to battery manufacturing, materials sourcing, and grid deployment.
Much of the technology race playing out globally centers on Tesla and China's BYD, the world's two most influential battery producers. Tesla's high-density 4680 cylindrical cells, built with nickel-manganese-cobalt chemistry, prioritize long range and fast charging but require sophisticated cooling to manage heat buildup. BYD's Blade battery uses lithium-iron-phosphate chemistry in a long, prismatic format that favors cost, safety, and thermal stability over extreme energy density. The Blade's LFP design distributes heat more evenly, lowering the risk of fire and reducing maintenance needs, while Tesla's approach supports higher performance suited to premium systems. Analysts say BYD's cost advantage – about $10 per kilowatt-hour less in material costs – and full vertical integration give it an edge in scaling grid applications, while Tesla's technology remains the benchmark for fast deployment and efficiency.
Utility-scale batteries now deliver far more than backup power. They earn revenue through grid-stabilization services, frequency regulation, and price arbitrage. By purchasing surplus wind or solar energy when wholesale prices collapse – sometimes below zero – and reselling it during peak demand, battery operators keep grids stable and renewable power profitable. In Spain, for instance, wholesale prices turned negative for over 500 hours in 2025 as midday solar generation flooded the grid. However, developers still face challenges navigating fragmented markets, uneven policy frameworks, and double-charging fees in some regions.
While investors contend with such policy and pricing barriers, a larger pattern is emerging: energy storage is becoming the pivot around which renewables operate. A July 2025 report by the Energy Transitions Commission found that "sunbelt" nations like India and Mexico, where solar generation follows predictable daily cycles, could meet nearly all balancing needs with batteries alone. By contrast, wind-dominant countries such as Germany and the United Kingdom will require hybrid systems that include pumped hydro, compressed-air storage, and hydrogen to bridge long-duration power gaps.
Image credit: The Financial Times
Container-sized batteries are powering the next global energy revolution
