Battery energy storage system

A battery energy storage system (BESS), battery storage power station, battery energy grid storage (BEGS) or battery grid storage is a type of energy storage technology that uses a group of batteries in the grid to store electrical energy. Battery storage is the fastest responding dispatchable source of power on electric grids, and it is used to stabilise those grids, as battery storage can transition from standby to full power in under a second to deal with grid contingencies.

Battery energy storage systems are generally designed to deliver their full rated power for durations ranging from 1 to 4 hours, with emerging technologies extending this to longer durations to meet evolving grid demands. Battery storage can be used for short-term peak power demand and for ancillary services, such as providing operating reserve and frequency control to minimize the chance of power outages.

They are often installed at, or close to, other active or disused power stations and may share the same grid connection to reduce costs. Since battery storage plants require no deliveries of fuel, are compact compared to generating stations and have no chimneys or large cooling systems, they can be rapidly installed and placed if necessary within urban areas, close to customer load, or even inside customer premises.

As of 2021, the power and capacity of the largest individual battery storage system is an order of magnitude less than that of the largest pumped-storage power plants, the most common form of grid energy storage. For example, the Bath County Pumped Storage Station, the second largest in the world, can store 24 GWh of electricity and dispatch 3 GW while the first phase of Vistra Energy's Moss Landing Energy Storage Facility can store 1.2 GWh and dispatch 300 MW. However, grid batteries do not have to be large — a high number of smaller ones (often as hybrid power) can be widely deployed across a grid for greater redundancy and large overall capacity. By 2025, global power capacity was 267 GW with 610 GWh energy capacity.

As of 2019, battery power storage is typically cheaper than open cycle gas turbine power for use up to two hours, and there was around 365 GWh of battery storage deployed worldwide, growing rapidly. Levelized cost of storage (LCOS) has fallen rapidly. From 2014 to 2024, cost halving time was 4.1 years. The price was US$150 per MWh in 2020, and further reduced to US$117 by 2023.

Battery storage power plants and uninterruptible power supplies (UPS) are comparable in technology and function. However, battery storage power plants are larger.

For safety and security, the actual batteries are housed in their own structures, like warehouses or containers. As with a UPS, one concern is that electrochemical energy is stored or emitted in the form of direct current (DC), while electric power networks are usually operated with alternating current (AC). For this reason, additional inverters are needed to connect the battery storage power plants to the high voltage network. This kind of power electronics include gate turn-off thyristor, commonly used in high-voltage direct current (HVDC) transmission.

Various accumulator systems may be used depending on the power-to-energy ratio, the expected lifetime and the costs. In the 1980s, lead-acid batteries were used for the first battery-storage power plants. During the next few decades, nickel–cadmium and sodium–sulfur batteries were increasingly used. Since 2010, more and more utility-scale battery storage plants rely on lithium-ion batteries, as a result of the fast decrease in the cost of this technology, caused by the electric automotive industry. Lithium-ion batteries are mainly used. A 4-hour flow vanadium redox battery at 175 MW / 700 MWh opened in 2024. Lead-acid batteries are still used in small budget applications.