Guide to Energy Storage

What Is Energy Storage?

Energy storage encompasses any technology that captures electrical energy for use at a later time. In the context of the modern power grid, storage is the critical complement to variable renewable generation — particularly solar and wind — because it decouples the moment of generation from the moment of consumption. A solar array produces maximum output at midday, but peak electricity demand in many regions occurs in the late afternoon and evening. Storage bridges this temporal gap, making renewable energy dispatchable.

The most commercially mature form of grid storage is lithium-ion battery energy storage systems (BESS), which account for the vast majority of new storage capacity additions in the US. However, the storage landscape is broader, encompassing pumped hydroelectric storage (the largest existing fleet), flow batteries, compressed air, gravity storage, and emerging technologies like hydrogen electrolysis and iron-air batteries.

In 2023 and 2024, the US installed more than 10 GW of battery storage per year — a rapid acceleration driven by IRA storage tax credits (standalone BESS now qualify for the 30% ITC), utility procurement programs, and the economic value of arbitrage in volatile wholesale electricity markets like ERCOT and CAISO.

Key Storage Providers and the Industry Landscape

The energy storage industry includes a mix of cell manufacturers, system integrators, software platform providers, and independent power producers who own and operate storage assets. Browse the full list of companies in the energy storage system providers category in the Bywatts database.

Battery Cell and Module Manufacturers

Cell manufacturing is dominated by Asian suppliers — CATL, BYD, Samsung SDI, LG Energy Solution, and Panasonic supply the lithium-ion cells used in most grid-scale BESS. IRA domestic content bonuses are creating incentives for US cell production: LG Energy Solution and SK On have announced US gigafactories, and several new entrants are targeting the grid storage market specifically.

System Integrators

Fluence (a joint venture of Siemens and AES), Tesla Energy (Megapack), BYD, CATL, and Powin are among the largest providers of packaged utility-scale BESS solutions. These companies supply containerized battery systems with integrated thermal management, power electronics, and battery management software. System costs for standalone utility BESS have fallen below $250/kWh installed in competitive markets.

Inverter and Power Electronics Suppliers

SMA, SolarEdge, Sungrow, and Huawei supply hybrid inverters used in co-located solar-plus-storage systems. Enphase's IQ Battery is widely used in residential storage, competing with Tesla's Powerwall and Franklin Electric's aGate. The residential segment is expanding rapidly as utilities shift to time-of-use (TOU) rates that make behind-the-meter storage economically attractive.

Software and Operations

Optimizing a storage asset across multiple revenue streams — energy arbitrage, frequency regulation, spinning reserve, capacity, and demand charge reduction — requires sophisticated software. Companies like Stem (now Anza), AutoGrid, Orasis Energy, and RTOS provide BESS optimization platforms. The analytics and operational layer is an area of rapid innovation and M&A activity.

Use Cases: Where Storage Creates Value

Energy storage can provide value at multiple points in the electricity system, and the economic case for a specific project depends on which revenue streams are accessible in a given market and regulatory context:

• Energy arbitrage: Charge during low-price (typically midday solar-abundant) hours, discharge during high-price evening hours. In ERCOT, price spreads of $100–$500/MWh or more during scarcity events create significant arbitrage value for fast-response storage.
• Ancillary services: Frequency regulation (response within seconds), spinning reserve, and non-spinning reserve are grid reliability services procured by grid operators. Battery storage can respond faster than any thermal generator, commanding premium payments in markets like PJM and CAISO.
• Capacity: Utilities and grid operators in capacity markets pay storage resources for the ability to deliver power during peak periods. Storage qualifies as a capacity resource if it can sustain output for the required duration (typically 4 hours).
• Solar integration and curtailment reduction: Co-located solar-plus-storage allows the system to absorb excess midday generation that would otherwise be curtailed, improving the overall project economics and reducing waste. California regularly curtails hundreds of MW of solar on spring days without sufficient storage to absorb the surplus.
• Behind-the-meter demand charge reduction: Commercial and industrial customers in markets with high demand charges can install storage to shave peak demand, often achieving payback periods of three to six years.
• Resilience and backup power: Distributed and community storage can provide backup power during grid outages, a growing value proposition in regions prone to wildfires, hurricanes, and winter storms. Paired with solar, a properly sized system can provide days of autonomous operation.

Storage on the Grid: Integration and Future Outlook

Energy storage is shifting from a niche peaking resource to a foundational element of grid planning. Several key trends are shaping the integration of storage into the US power system:

Duration expansion: The current fleet is predominantly 2- to 4-hour lithium-ion storage. As solar penetration increases, grid operators are procuring longer-duration storage (8+ hours) to address the "duck curve" — the steep evening ramp that occurs as solar generation falls and demand rises. Technologies including iron-air (Form Energy), vanadium flow batteries (VRX Energy, Invinity), and pumped hydro are being developed to serve the long-duration segment.

Interconnection and siting: Storage projects face many of the same interconnection queue challenges as solar. Co-location with existing solar or wind projects can expedite interconnection by sharing existing grid connections and permits. Some states are creating dedicated interconnection pathways for storage-only projects.

Transmission and distribution: Grid operators are exploring "non-wires alternatives" — using distributed storage to defer or avoid expensive transmission and distribution upgrades. FERC Order 841 requires ISOs to allow storage to participate in wholesale markets, and Order 2222 allows distributed resources (including behind-the-meter storage) to aggregate and participate in wholesale markets through virtual power plants.

Regional deployment patterns: Storage deployment tracks solar and wind penetration. California leads the nation in operational BESS, driven by CAISO's capacity requirements and duck-curve management needs. Texas is the fastest-growing storage market, propelled by ERCOT's energy-only market and extreme weather volatility. The Southeast, PJM territory, and the Mountain West are emerging markets. Explore the interactive power infrastructure map to see storage and generation assets overlaid.

Technology roadmap: Lithium-ion costs are projected to continue declining through at least 2030 as gigafactory capacity expands. Sodium-ion batteries are entering the utility market as a lower-cost, more geographically diverse alternative to lithium. Solid-state batteries offer potential safety and energy density improvements for vehicles but are unlikely to dominate grid storage within this decade. The long-duration segment remains contested, with multiple chemistries and mechanical approaches still competing for commercial viability.