What Is Battery Energy Storage?

Renewable energy is changing how electricity is produced across the United States. As more solar and wind projects come online, another technology is becoming increasingly important: battery energy storage.

Battery Energy Storage Systems (BESS) allow electricity to be stored and used later instead of being consumed the moment it is generated. This added flexibility can help support grid reliability, improve the use of renewable energy, and provide backup power in certain situations.

According to the U.S. Department of Energy, energy storage plays an important role in creating a more resilient, flexible, and reliable electric grid by helping balance electricity supply and demand (https://www.energy.gov/oe/energy-storage).

This article explains what battery energy storage is, how it works, and why it has become an important part of today's electricity system.

This article is for educational purposes only and does not constitute engineering, legal, or investment advice.

What You'll Learn

In this article, we'll cover:

• What battery energy storage is

• How battery energy storage systems work

• Common battery technologies

• Why battery storage supports grid reliability

• How batteries work alongside renewable energy

• Common applications for battery storage

What Is Battery Energy Storage?

Battery Energy Storage Systems (BESS) store electricity so it can be used later when it is needed.

Unlike power plants that generate electricity, battery systems do not create electricity themselves. Instead, they store electricity produced by other sources, including solar farms, wind projects, or the electric grid, and discharge it when demand increases or when generation decreases.

The U.S. Department of Energy describes energy storage as an important tool for improving grid flexibility by allowing electricity generated at one time to be used at another (https://www.energy.gov/oe/energy-storage).

How Do Battery Energy Storage Systems Work?

Battery storage generally follows three basic steps.

Charging

Electricity flows into the battery from the grid or from an electricity generation source such as a solar or wind facility.

Storing

The battery stores the electrical energy in chemical form until it is needed.

Discharging

When electricity demand increases, renewable generation decreases, or grid operators request additional power, the battery releases stored electricity back into the grid or to connected facilities.

The exact operation depends on the battery technology, system design, operating software, and the needs of the electricity system.

Why Is Battery Storage Important?

Electricity demand changes throughout the day.

People typically use more electricity during certain hours, such as in the morning when businesses open or during the evening when households return home.

At the same time, renewable electricity generation can fluctuate depending on weather conditions and the time of day.

Battery storage helps bridge these differences by storing electricity when supply exceeds demand and making it available later when additional electricity is needed.

The U.S. Department of Energy notes that energy storage can improve reliability, enhance grid resilience, and support greater integration of renewable energy resources (https://www.energy.gov/oe/energy-storage).

How Battery Storage Supports Renewable Energy

Renewable energy sources do not always generate electricity continuously.

For example:

• Solar facilities produce electricity only when sunlight is available.

• Wind turbines generate electricity when wind conditions are suitable.

Battery storage allows some of this electricity to be stored rather than going unused during periods of lower demand.

Later, when renewable generation decreases or electricity demand rises, stored electricity can be discharged to help meet system needs.

Battery storage does not eliminate the variability associated with renewable energy, but it can help improve operational flexibility within the broader electricity system.

The National Renewable Energy Laboratory (NREL) provides additional information on the role of energy storage in supporting renewable energy integration (https://www.nrel.gov/grid/energy-storage.html).

Common Battery Technologies

Several battery technologies are used across the electricity sector.

Lithium-Ion Batteries

Lithium-ion batteries are currently among the most widely deployed battery technologies for grid-scale energy storage because of their high energy density, relatively fast response times, and declining costs.

The U.S. Department of Energy discusses lithium-ion batteries as one of several commercially available storage technologies (https://www.energy.gov/oe/energy-storage).

Flow Batteries

Flow batteries store energy in liquid electrolytes contained in external tanks.

Depending on system design, they may offer longer discharge durations and different operating characteristics than lithium-ion batteries.

The Department of Energy identifies flow batteries as one of several technologies being developed for long-duration energy storage applications (https://www.energy.gov/energy-storage-grand-challenge).

Other Storage Technologies

Energy storage also includes technologies beyond batteries, such as:

• Pumped-storage hydropower

• Compressed air energy storage

• Thermal energy storage

• Emerging long-duration storage technologies

Different technologies are designed for different operating needs, durations, and grid applications.

Common Uses of Battery Energy Storage

Battery storage can support the electricity system in many different ways.

Supporting Peak Electricity Demand

Electricity demand is not constant throughout the day.

Battery systems can discharge stored electricity during periods of higher demand, potentially reducing pressure on the broader electricity system.

Supporting Renewable Energy Integration

Battery storage can help manage changes in renewable electricity generation by storing excess electricity and delivering it later when renewable output changes.

Improving Grid Reliability

Grid operators may use battery storage to help maintain system stability and respond quickly to changing operating conditions.

Supporting Backup Power

Some battery systems are designed to provide backup electricity for homes, businesses, hospitals, or critical infrastructure during certain outages or emergencies, depending on system configuration.

Not every battery installation serves every purpose, and system capabilities vary depending on project design.

Can Battery Storage Replace the Electric Grid?

No.

Battery storage complements the electric grid rather than replacing it.

The grid continues to provide electricity generation, transmission, and distribution across the country.

Battery storage is one of several technologies that can improve flexibility and help manage changing electricity needs within the existing system.

The Department of Energy explains that energy storage works alongside other grid resources to improve overall system performance rather than serving as a standalone replacement (https://www.energy.gov/oe/energy-storage).

Why This Matters

As electricity demand continues to evolve and renewable energy deployment expands, battery storage is expected to play an increasingly important role in supporting electricity systems.

Storage technologies can help improve operational flexibility, support grid reliability, integrate renewable resources, and enhance resilience under a wide range of operating conditions.

The specific benefits of any battery project depend on its design, location, operating strategy, applicable regulations, and the characteristics of the local electricity system.

Final Thoughts

Battery energy storage has become an important part of today's energy infrastructure.

Rather than generating electricity, batteries provide the ability to store electricity and deliver it when it is needed most.

As renewable energy continues to grow, battery storage is expected to remain an important technology for supporting grid operations, improving flexibility, and strengthening electricity infrastructure across the United States.

Understanding how battery storage works provides useful context for discussions about renewable energy, electricity reliability, and the future of the electric grid.

Further Reading

• U.S. Department of Energy – Energy Storage: https://www.energy.gov/oe/energy-storage

• U.S. Department of Energy – Energy Storage Grand Challenge: https://www.energy.gov/energy-storage-grand-challenge

• National Renewable Energy Laboratory – Energy Storage: https://www.nrel.gov/grid/energy-storage.html

• U.S. Energy Information Administration – Battery Storage in the United States: https://www.eia.gov/todayinenergy/detail.php?id=54939