Chapter 7. Battery Energy Storage

Introduction

Energy storage, particularly Battery Energy Storage Systems (BESS), has rapidly emerged as a pivotal ancillary service within the electric power grid, transitioning from a nascent concept to a commercially viable and rapidly growing industry. Recent years have witnessed an exponential increase in deployed energy storage capacity, driven by the escalating integration of intermittent renewable energy sources like solar and wind, coupled with the critical need for enhanced grid reliability and efficiency. The global market for grid-scale electricity storage technologies is projected to grow significantly, with forecasts indicating a compound annual growth rate (CAGR) of 30.0% from $40.7 billion in 2024 to $151.2 billion by the end of 2029. This growth underscores a broader shift in investments towards energy storage and ongoing grid modernization efforts.[1]

A Battery Energy Storage System (BESS) consists of battery cells assembled in series to increase DC voltage and in parallel to increase current capacity.  There are numerous ways of grouping battery cells to make a larger system.  The assembled cells are encased in packaging and called a “pack” or a “module”.  The modules are put in series to further increase voltage, and that grouping is called a “string”,  “array”,  or “rack”.  There may be several strings in series that make up the battery sub-system connected to a single inverter station.  Usually batteries are grouped in a single enclosure and called a “container” or “enclosure”.   Multiple sub-systems of inverters are tied together to make the full BESS plant.

The maturity of energy storage technology for grid applications varies across different types, but advancements, particularly in lithium-ion batteries, have brought them to the forefront. While pumped hydro storage remains the most mature and widely deployed long-duration storage technology, newer battery chemistries are gaining traction for their longevity and safety. The industry is also exploring innovative approaches such as “second life” batteries from electric vehicles, further contributing to technological maturity and cost-effectiveness. The increasing focus on standardization of equipment and procurement, alongside improved safety testing and regulations (e.g., NFPA 855 and UL9540A), indicates a maturing market with robust industrial practices.

Technical advances have been instrumental in enabling grid-scale energy storage. Innovations in battery chemistry, power electronics, and sophisticated energy management systems (EMS) have significantly improved the efficiency, lifespan, and safety of storage solutions. These technological leaps allow BESS to respond in milliseconds to grid fluctuations, providing dynamic support that was previously challenging or impossible to achieve with traditional generation assets. The integration of artificial intelligence (AI) and machine learning into smart grids further optimizes energy distribution and load balancing, enhancing the overall performance of storage systems.

Energy storage plays a crucial role in large load facilities (e.g., industrial plants, data centers, large commercial buildings) by providing a wide range of benefits that enhance operational efficiency, reduce costs, and improve reliability and sustainability. Here are the common uses:

• Peak Shaving and Demand Charge Reduction: This is one of the most significant economic drivers for energy storage in large facilities. Electricity bills often include “demand charges” based on the highest power consumption recorded during a billing period (the “peak demand”). By discharging stored energy during these peak periods, facilities can reduce their reliance on the grid and “shave off” these expensive peaks, leading to substantial cost savings over the year.
• Load Shifting/Time-of-Use Optimization: Electricity prices often vary throughout the day, with higher rates during peak demand hours (e.g., afternoon and early evening) and lower rates during off-peak hours (e.g., overnight). Energy storage allows facilities to charge their batteries when electricity is cheap (off-peak) and discharge it when prices are high (on-peak), optimizing their energy purchases and reducing overall electricity costs.
• Integration of Renewable Energy Sources: Large facilities are increasingly incorporating onsite renewable energy generation like solar panels or wind turbines. However, these sources are intermittent (solar only generates when the sun shines, wind when it blows). Energy storage systems capture excess renewable energy when it’s abundant and store it for use when renewable generation is low or demand is high, effectively making renewable energy dispatchable and maximizing its self-consumption.
• Backup Power and Grid Resilience: Energy storage systems can provide critical backup power during grid outages, ensuring uninterrupted operations for essential processes, data centers, or critical infrastructure. This improves reliability and prevents costly downtime, lost production, or data loss. In some cases, facilities can “island” from the main grid and operate autonomously using their energy storage and onsite generation (forming a microgrid).
• Ancillary Services and Grid Support: Some large facilities with energy storage can participate in demand response programs or offer grid services to the utility. This includes 1) Frequency Regulation by rapidly injecting or absorbing power to help stabilize grid frequency; 2) Voltage Support by helping to maintain stable voltage levels on the grid; and 3) Reducing electricity consumption from the grid in response to utility signals during periods of high demand or grid stress, often receiving incentives for doing so.
• EV Charging Infrastructure Support: With the growth of electric vehicle fleets, large facilities often need to manage significant power demands from EV charging stations. Energy storage can help by storing power during low-demand periods and supplying it during peak charging times, preventing grid overloads and reducing demand charges associated with high EV charging loads.
• Power Quality Improvement: Energy storage can help mitigate power quality issues like voltage sags, swells, or momentary interruptions, ensuring a stable and clean power supply for sensitive equipment.

In essence, energy storage empowers large load facilities to become more active participants in their energy management, moving beyond simply consuming electricity to strategically managing its flow, cost, and reliability.

1 Deployment Schedule

Implementing an energy storage system (ESS) as a generator for large-load facilities offers a faster deployment timeline compared to traditional generation technologies. This advantage stems from the standardized, modular, and transportable design of battery energy storage system (BESS) components, which simplifies design, installation and commissioning. In recent years, BESS deployments have consistently outpaced other generator types in speed and scalability, making them an attractive solution for facilities requiring rapid power solutions. The typical deployment schedule for a battery energy storage system (ESS) takes from 1.5 year to 3 years.

Development

The development phase of a Battery Energy Storage System (BESS) project includes identifying operational requirements, evaluating technical and economic feasibility, selecting an appropriate site, and crafting a conceptual design. While this process was considered pioneering a decade ago, the rapid maturation and scaling of the technology have provided a growing body of completed projects that now serve as valuable templates for new developments. In most cases, the business development components—such as securing offtake agreements, navigating regulatory pathways, and structuring financing—tend to take longer than the technical design and engineering. For BESS installations dedicated to serving large, consistent loads, the primary application is typically well-defined from the outset.

Permitting & Regulatory Approvals

Like other developments, one of the earliest permitting tasks is environmental studies, which are significantly less complicated compared to other generation technologies.  There are additional local, state, and federal permitting requirements, including land use, zoning, and safety regulations.  An initial interconnection assessment with the utility is also essential to gauge grid capacity and requirements. Obtaining permits from local authorities, such as building, electrical, and civil permits, can be time-consuming if the local offices are not familiar with energy storage projects.

Given the fire safety concerns associated with large battery energy storage systems, Fire Marshal permission requires early and continuous engagement with local Fire Marshals and fire departments. This involves adhering to codes like NFPA 855 (Standard for the Installation of Stationary Energy Storage Systems), submitting detailed fire safety plans, outlining emergency response protocols, and potentially conducting large-scale fire testing in accordance with UL9540A. Approvals can be contingent on specific ventilation, suppression, and setback requirements, which have become clearer in recent years.

Interconnection

The interconnection agreement process with the utility involves detailed studies (e.g., system impact studies, facilities studies) to determine the ESS’s effect on the grid and identify necessary upgrades. Utility queues can be long, and the cost and timeline of required grid upgrades can be substantial. The unique operational attributes of energy storage are not always well-accounted for in existing interconnection processes, potentially leading to undue burdens. However, most utilities are developing better processes for energy storage.

Procurement

Supply chain tasks are relatively straight forward for ESS components, particularly batteries (e.g., lithium-ion cells), inverters, transformers, and switchgear. Geopolitical factors, raw material availability, manufacturing capacity, and shipping delays could extend lead times by months or even a year, impacting the overall project schedule and cost. It’s crucial to identify and order long-lead time equipment, such as transformers, as early as possible, as they can have lead times exceeding multiple years. The process of vendor qualification and ensuring their products meet technical specifications and safety standards can also add considerable time to this phase.

The Battery Energy Storage System (BESS) market is experiencing rapid growth and innovation, with a diverse range of companies supplying solutions for industrial and utility-scale applications. These suppliers often specialize in different aspects, from battery cell manufacturing to full system integration. Most of the leading battery manufactures also offer full integrated battery energy storage systems. Some of these include:

• CATL (Contemporary Amperex Technology Co. Ltd.): A China based global leader in lithium-ion battery manufacturing, CATL is a major supplier of battery cells for both electric vehicles and energy storage systems and is increasingly expanding into system integration.
• BYD: A China based multinational known for its electric vehicles, BYD is also a significant player in BESS, offering a wide range of integrated solutions for various applications, from residential to utility-scale.
• LG Energy Solution: A spin-off of LG Chem, LG Energy Solution based in South Korea is one of the world’s largest producers of lithium-ion batteries and a prominent supplier of BESS for diverse markets, including grid-scale and residential.
• Samsung SDI: Another South Korean based conglomerate, Samsung SDI is a leading manufacturer of high-performance lithium-ion batteries for BESS applications, supporting renewable energy projects and providing backup solutions.

There are also several companies that buy batteries from various suppliers and focus on the systems integration and operational services.  This approach can benefit with the ability to rapidly shift to a new battery technology.  Some of the companies that fall into this category include:

• Fluence: A joint venture between Siemens and AES, Fluence is a leading global provider of energy storage products, services, and software, focusing on utility-scale and large commercial/industrial applications.
• Hitachi Energy: Offers advanced energy storage solutions and services for grid modernization and renewable integration.
• Wartsila: A world leader in BESS deployments including hardware and energy optimization software.
• GE Vernova: A key player in grid-scale BESS solutions, contributing to utility and industrial projects globally.
• Sungrow: A leading global inverter supplier that has also become a top BESS integrator, especially strong in Asia-Pacific.
• Tesla: A trailblazer in electric vehicles, Tesla Energy has rapidly grown its energy storage business with products like the Powerwall (residential) and Megapack (utility-scale), offering highly integrated solutions.

The market is dynamic, with new players emerging and existing companies expanding their offerings. Many of these suppliers offer comprehensive solutions that include not only the battery hardware but also power conversion systems (inverters), battery management systems (BMS), and energy management software (EMS).

Construction and Start-Up

Since energy storage is a relatively new technology, finding workers with the skills, or training workers can add length to the construction schedule. Throughout construction, construction permitting inspections by local authorities (building inspectors, electrical inspectors, fire marshals) are regularly required. The major components of BESS systems are UL listed, which simplifies permitting and inspections at the site. Additionally, site-specific challenges like unforeseen ground conditions, adverse weather, or logistical hurdles in material delivery can impact the construction timeline.

The final phase involves rigorous testing of all components and systems to ensure they operate as intended and integrate seamlessly with the facility’s existing infrastructure and the grid. Interconnection testing with the utility is comprehensive, verifying proper grid synchronization, safety protocols, and operational compliance.  Performance testing ensures that the BESS meets specified performance guarantees (e.g., capacity, efficiency, response time); if performance falls short, troubleshooting and adjustments are necessary. Crucially, software and controls integration ensure the BESS control system integrates correctly with the facility’s energy management system and any utility communication protocols.

2 Operational Capabilities

Energy storage systems (ESS) are transformative assets in modern electricity grids, providing a range of operational capabilities that fundamentally change how power is generated, delivered, and consumed. Unlike traditional power plants, which primarily operate in a single direction (generating power), ESS can both absorb and inject electricity, offering unparalleled control and responsiveness.

Dispatchability and Flexibility

BESS are inherently highly dispatchable, meaning their output can be controlled precisely and on demand. Unlike intermittent renewable sources like solar (dependent on sunlight) or wind (dependent on wind speed), an ESS can be commanded to charge or discharge a specific amount of power at a specific time, irrespective of ambient conditions, as long as it has stored energy or room to charge. This allows them to function like traditional power plants, providing power when needed.  However, they are not sources of energy and can only discharge for hours at a time before they need to recharge.

The operational flexibility of ESS is a core strength. They can rapidly switch between charging (acting as a load) and discharging (acting as a generator). This bidirectional capability, combined with their quick response, allows them to provide multiple grid services simultaneously or sequentially. They can respond to price signals, grid imbalances, or emergency situations with high precision.

Start Times and Ramp Rates

BESS boast near-instantaneous start-times and extremely fast ramp rates. They can typically go from a dormant state to full 100% power output within milliseconds to a few seconds (e.g., < 100 ms to ~2 seconds), depending on the system design and grid requirements. This rapid ramping capability is crucial for balancing sudden fluctuations in renewable generation or load. This contrasts sharply with traditional thermal generators, which can take minutes to hours to start up and synchronize.

Grid Stability and Power Quality

Traditional synchronous generators inherently provide inertia to the grid, resisting sudden changes in frequency. While most inverter-based ESS do not naturally provide physical inertia, they can offer synthetic inertia or grid-forming capabilities through advanced inverter controls. These “grid-forming” inverters can rapidly detect frequency deviations and inject or absorb power to counteract them, mimicking the effect of inertia. This rapid electronic response can often be faster and more precise than the mechanical response of traditional generators, helping to maintain grid stability and prevent cascading failures. Inverters combined with energy storage have the capability to provide longer support functions over solar and wind inverters.

Battery energy storage system (BESS) inverters are at the forefront of advancing grid power quality through their ability to provide precise, real-time control of voltage, frequency, and reactive power. Unlike traditional generators, modern BESS inverters are equipped with sophisticated power electronics and control algorithms that enable them to actively correct power factor, filter harmonics, and stabilize voltage fluctuations. These capabilities allow BESS units to function not only as energy providers but also as grid-support assets, improving reliability and reducing stress on aging infrastructure. Additionally, their fast response times make them ideal for dynamic grid services such as frequency regulation and voltage support, especially in systems with high penetration of intermittent renewables. As inverter technology continues to evolve, BESS is becoming a critical tool for enhancing power quality and enabling a more resilient and flexible electric grid.

Synchronization and Control

The process of connecting BESS to the grid involves synchronization – matching the BESS’s voltage, frequency, and phase angle with that of the grid. Thanks to sophisticated power electronics and inverters, BESS can achieve synchronization very rapidly, typically within tens of milliseconds to a few seconds after receiving a command. This allows for quick connection and disconnection from the grid, crucial for providing services like black start (restarting the grid after an outage) or rapid grid support.

Parasitic Loads and Degradation

Battery energy storage systems (BESS) do have parasitic loads—internal systems that consume power to maintain safe and reliable operation. Key parasitic components include the HVAC system, which regulates temperature to keep battery cells within optimal operating ranges, especially in hot or cold climates; the battery management system (BMS), which monitors cell voltage, temperature, and state of charge to prevent failures; and control and communication systems, which manage grid interactions, fire safety protocols, and performance optimization. These parasitic loads typically consume between 0.5% to 2% of the total system power rating during a charge or discharge cycle, depending on the C-rate, climate conditions, and technology used. During standby, the parasitic load drops to less than 0.1%.  While relatively small, these loads must be accounted for in energy yield calculations and can influence system sizing and operational efficiency.

3 Service Reliability

Availability & Failures

The reliability of Battery Energy Storage Systems (BESS) is high and is continuously improving with technological advancements and operational experience. Mean Time Between Failure (MTBF) of System Components: MTBF is a key metric indicating the average time a repairable system or component operates correctly between failures. For BESS, it’s a composite of various sub-components, any of which could disrupt operation:

• Battery Cells/Modules: While specific published MTBF values for individual battery cells or modules are not widely publicized by manufacturers due to proprietary data and varying usage conditions, industry estimates suggest that high-quality battery cells are designed for a lifespan measured in thousands of cycles (e.g., 5,000 to 10,000+ cycles) and often come with warranties ranging from 10 to 20 years. Failures at the cell or module level are typically addressed by the Battery Management System (BMS) isolating the faulty unit, preventing a system-wide shut down. [2]
• Power Conversion Systems (PCS) / Inverters: These electronic components are sophisticated and can have MTBFs ranging from 50,000 to 200,000+ hours. Factors like operating temperature, electrical stress, and component quality significantly influence their reliability.
• Battery Management Systems (BMS) and Control Systems: As the “brain” of the BESS, these systems are designed for high reliability. Their MTBF can also range significantly, often tens of thousands to hundreds of thousands of hours, depending on the complexity and redundancy built into the control architecture.
• Ancillary Equipment (HVAC, Fire Suppression): The reliability of these supporting systems is also crucial. While individual component MTBFs vary, ensuring their proper function through regular maintenance is key to overall system reliability. [3]

The overall plant availability of a BESS, representing the percentage of time it is ready and able to perform its intended functions, is generally high. Reports for operational BESS in grid-scale applications often show availability in the range of 95% to 99%. For instance, some reports for ERCOT battery energy storage systems in 2023 indicated an average availability for commercial operations of 97%. Achieving high availability is crucial for maximizing revenue streams, especially in volatile electricity markets where being offline during critical high-price periods can lead to significant missed opportunities. [4]

Redundant and Resilient Architecture

Redundancy Strategies to Improve Reliability: To enhance reliability and ensure high availability, BESS designs often incorporate various redundancy strategies:

• N+1 or 2N Configuration: This involves installing more capacity than strictly required (N+1) or even doubling critical components (2N, where every component has a dedicated backup). For example, having extra battery strings, power conversion units, or control modules allows the system to continue operating, albeit sometimes at a reduced capacity, if one component fails.
• Modular Design: BESS are typically built with modular battery racks and PCS units. This modularity allows for easier isolation of a faulty module or unit for maintenance or replacement without impacting the entire system’s operation.
• Fault-Tolerant Controls: Advanced control systems are designed to detect failures, isolate faulty components, and reconfigure the system automatically to maintain operation. This might include bypass switches at the module or string level to remove a failing battery from the circuit.
• Redundant Communication Pathways: Ensuring multiple communication routes between critical components and the control center mitigates the risk of a single point of failure.

External Risks

Risks to Reliability and Interruptions: Despite high design reliability and redundancy, several factors can pose risks to BESS operational reliability:

• Weather Events: Extreme weather, such as intense heat, severe cold, floods, or high winds, can impact BESS performance or cause physical damage. Batteries have optimal operating temperature ranges, and deviations can lead to degraded performance or accelerated aging. External infrastructure like cooling systems can also be affected by weather.
• Faults in Related Infrastructure: The BESS relies on external infrastructure like the grid connection, transformers, and switchgear. Faults or outages in these upstream or downstream systems can interrupt the BESS’s ability to charge or discharge, even if the BESS itself is fully functional.
• Cybersecurity Threats: As BESS become more integrated with grid operations and rely on sophisticated software, cybersecurity risks can impact their reliability. A cyberattack could disrupt control systems, leading to operational interruptions or even damage.

Maintaining high BESS reliability requires a holistic approach, combining robust design, redundant components, advanced monitoring, proactive maintenance, and comprehensive emergency response planning for various potential scenarios.

4 Environmental Sustainability

Energy storage systems (ESS), particularly battery energy storage systems (BESS), are central to the transition to a sustainable energy future. Their environmental footprint and community acceptance are complex topics that span their entire lifecycle, from raw material extraction to end-of-life management.

Emissions & Air Quality Impacts

In terms of direct operational emissions, BESS are remarkably clean. They do not burn fuel, thus producing zero greenhouse gas emissions (CO2, methane), nitrogen oxides (NOx), sulfur oxides (SOx), or particulate matter during their charge and discharge cycles. However, they have associated emissions from the energy source that charges the energy storage system.

The environmental impact of BESS shifts to the manufacturing of the batteries. The extraction of raw materials (e.g., lithium, cobalt, nickel, manganese) and the battery manufacturing process are energy-intensive and can involve significant carbon emissions. As the industry matures, there’s a growing focus on reducing these embedded emissions through cleaner manufacturing processes and renewable energy-powered factories.

Water Use

During operation, BESS typically require no water consumption, as almost all BESS systems use closed-loop liquid cooling or air cooling.  Water availability may be required for fire protection, unless other means are provided.  Being completely independent of a water supply gives battery energy storage a lot of flexibility for location.

End of Life and Recyclability

Lithium-ion batteries used in battery energy storage systems (BESS) are increasingly being designed with end-of-life recyclability in mind, as the industry seeks to reduce environmental impact and recover valuable materials. New companies such as Li-Cycle, Redwood Materials, ABTC, and Retrieve Technologies specialize in recycling battery materials. At the end of their service life—typically after 10 to 20 years—these batteries contain recoverable components such as lithium, cobalt, nickel, copper, and aluminum, which can be extracted through mechanical and chemical recycling processes. However, the recyclability rate depends on the battery chemistry and the recycling technology used. Current methods can recover up to 90% of key metals, though challenges remain in scaling these processes economically and safely. As regulations tighten and demand for critical minerals grows, investment in closed-loop recycling systems is accelerating, making lithium battery recycling a vital part of sustainable energy storage deployment.

Hazardous Materials & Waste Management

Lithium-ion batteries contain several hazardous materials that must be carefully managed at the end of their life to prevent environmental and health risks. Key hazardous components include: toxins like lithium hexafluorophosphate (LiPF₆), heavy metals, flammable materials, and fluorinated compounds. To manage these hazards, end-of-life batteries are typically processed through specialized recycling facilities that follow strict environmental and safety protocols. Regulations such as the EPA’s Universal Waste Rule in the U.S. [5] and EU Battery Directive [6] require proper labeling, transportation, and disposal procedures to minimize risks.

5 Site Feasibility

Proximity to Energy Resources & Infrastructure

Location selection for BESS has a high degree of flexibility. BESS facilities are generally more readily accepted in industrial or rural areas due to lower population density and fewer concerns regarding noise or visual impact. Proximity to existing electrical substations is highly desirable, as it minimizes grid interconnection costs and complexity.  Developers also prioritize avoiding sensitive areas such as national parks, nature reserves, flood zones, or sites of special scientific interest, and they typically favor land that is not considered “best and most versatile” agricultural land.  Roads and bridges leading to the selected site must also be able to handle the weight of heavy equipment required for transport and installation.

Land Use & Power Density

BESS integrated with containerized batteries, inverter/charger, and MV transformers come in packages with a 3 to 10 MWh that take up 800 to 1500 ft2 including the necessary clearances.  With additional access paths, auxiliaries, switchgear and boundary clearances, a 100-megawatt, 4-hour BESS system can occupy as little as 5 acres acre of land, or around 80 MWh/acre.   There have been efforts to increase this density by stacking battery racks vertically, however safety and logistical concerns have kept such deployments limited to date.  This power density is relatively high for generator systems.

Aesthetics & Acoustic Considerations

Visual impact is a minimal concern, often addressed through screening with architectural features, earth berms, or landscaping. The height of the facility is also a consideration; battery storage in outdoor areas generally do not exceed 10 feet (3048 mm), aligning with typical building height limits in applicable zoning regulations. As with any development, municipalities have specific zoning and noise ordinances that would dictate the permissible parameters for BESS facilities, necessitating detailed compliance plans including noise studies and mitigation strategies to meet local limits.

While considerably quieter than other generators, BESS facilities generate noise from cooling systems, inverters, and transformers, with levels that can range from 70 to 92 decibels at 1 meter from the equipment and drop to less than 40 dBa at the site boundary. The cooing units contribute the most noise due to the sheer number of them that might be operating at the same time.  Mitigation measures like acoustic fencing could be used to comply with local noise ordinances if equipment is close to a boundary.

Public Perception & Perceived Harm

Active and transparent community engagement from the earliest stages of a project is essential for addressing concerns, building trust, and securing “social license.” The primary community concerns often revolve around safety, particularly fire risk and potential thermal runaway events associated with lithium-ion batteries. Residents worry about toxic gas release during fires, explosion risks due to gas accumulation, and potential groundwater contamination from firewater runoff or chemical leaks. Noise pollution from cooling systems or transformers is also a concern, as is the visual impact of large battery containers or structures. BESS projects are generally more readily accepted in industrial and rural areas compared to residential areas.

However, communities can also see significant benefits. BESS can improve grid reliability and resilience, offering backup power during outages, reducing the need for new, polluting peaker plants in their vicinity, and enabling higher levels of local renewable energy integration. For urban or rural communities, they can defer expensive transmission/distribution upgrades, potentially leading to lower electricity costs and enhanced energy independence. Projects also offer economic benefits through local jobs during construction and operation, and property tax revenues.

6 Evolving Policy

The energy storage business, while experiencing rapid growth and proving its critical role in grid modernization, faces several policy and regulatory risks that challenge its full potential. These issues often stem from existing frameworks that were designed for a centralized, one-way power flow from large fossil fuel generators, rather than the dynamic, bidirectional, and flexible nature of energy storage. These risks can, and often do, prevent projects from moving forward or significantly delay their development and operation.

Policy Volatility

One of the most persistent and impactful challenges is interconnection policy and process for energy storage systems. The regulations governing how energy storage systems (ESS) connect to the grid are frequently complex, lengthy, and inconsistent across different jurisdictions and utility service territories.  Existing interconnection rules may not adequately account for the unique operational attributes of ESS, such as their ability to rapidly charge and discharge or provide multiple grid services. This can lead to overly conservative impact studies that mandate costly and time-consuming grid upgrades, or even outright deny interconnection, making projects economically unviable.  For example, some regulations may still “double charge” ESS as both a load when charging and a generator when discharging, leading to excessive transmission and distribution fees that erode profitability. [7] In 2018, and updated in 2021, FERC released Order 841 and 845 requiring ISOs and RTOs to integrate energy storage into wholesale markets without unfair treatment. [8]

Safety regulations and permitting consistency also pose considerable challenges. While national standards like NFPA 855 (Standard for the Installation of Stationary Energy Storage Systems) and UL 9540 (Energy Storage Systems and Equipment) exist, their adoption and interpretation vary significantly at state and local levels. Local Authorities Having Jurisdiction (AHJs), such as municipal building departments and Fire Marshals, may lack extensive experience with large-scale BESS, leading to uncertainty in applying codes, requests for unique or additional documentation, and prolonged review periods. To address these concerns, several organizations have recently put forth reports such as the EPA’s “BESS Safety Toolkit” [9], while training institutions have started safety programs for first responders such as the TEEX  “Electric Vehicle and Stored Energy Summit”. [10]

Incentives

The economics of BESS projects in the U.S. currently benefit from the Investment Tax Credit (ITC), extended by the Inflation Reduction Act to include standalone energy storage and adding bonus credits for domestic content or siting in “energy communities”.  The One Big Beautiful Bill Act of 2025 preserved incentives for BESS although added stricter supply chain compliance with Foreign Entity of Concern rules which included China, who is a major supplier of batteries and battery materials. [11] State-level incentives, such as procurement targets (e.g., California, New York, Massachusetts with mandates for specific MW/MWh targets), rebates, or performance-based incentives, also play a vital role. The stability and long-term clarity of these incentives are always a risk.

7 Cost of Capacity & Energy

Over the past decade, the cost of large-scale stationary energy storage systems (ESS)—primarily powered by lithium-ion battery technology—has dropped significantly, making them increasingly viable for grid applications. While evaluating cost, it’s important to recognize that ESS units function as both a support and an extension of generation capacity. Though often classified as “generators” within the electrical system, they do not produce energy independently and must be paired with other power sources to charge and discharge effectively.

Capital and Operational Expenditures

For large-scale stationary BESS, expenditures are often expressed in terms of dollars per megawatt ($/MW) for power capacity and dollars per megawatt−hour ($/MWh) for energy capacity. The size of the power conversion system determines the power rating (MW).  The quantity of batteries in the system makes up the energy rating (MWh).  Alternatively, the energy rating is expressed in Hours, calculated by dividing the system’s energy rating (MWH) by its power rating (MW).  To ensure clarity, cost estimates for energy storage systems must include the power and energy rating.

Capital Expenditures (CAPEX) can be broken into major components.Batteries constitute the largest portion of CAPEX, ranging from approximately $100 to $200 per kilowatt-hour (kWh) of capacity.  The Power Conversion Systems (PCS), which includes the Inverter and Charger, typically range from $30 to $90 per kilowatt (kW) of power. The Balance of System (BOS) Components, which includes all other necessary hardware, such as the Battery Management System (BMS), energy management system (EMS), cooling systems (HVAC), fire suppression, electrical wiring and cabling, transformers, switchgear, and structural supports (e.g., containers, buildings), costs can add an additional 20% to 30% to the overall system cost. Installation expenses encompass labor, site preparation, transportation, permitting, and engineering design, and account for about 20 to 30 % of system cost.  Combining these components, the total installed CAPEX for a large stationary lithium-ion BESS can be approximated as the combination of $150,000 per MW of power PLUS $200,000 per MWh of energy.

OPEX includes the ongoing costs associated with operating and maintaining an ESS throughout its lifespan. These are typically categorized into fixed and variable costs.  Fixed Operational Costs include items such as rent for the land, property taxes, and insurance, required maintenance, and standby power losses, which range from $10,000 to $20,000 per MW per year. Variable Operational Costs fluctuate with the system’s usage and performance and include auxiliary power and losses due to charging and discharging, the cost of electricity to charge the system, and the cost to augment the batteries to maintain energy capacity as the batteries degrade.

One of the most significant operational expenses for BESS is the cost of electricity to charge the system, which is functionally equivalent to the “fuel cost” associated with conventional generators.  More energy goes into the BESS system than is discharged out.  Energy is lost from the batteries during charging and discharging, and energy is lost in inefficiencies of the power conversion system, wires and transformers.  Auxiliary power is required to cool and control the equipment during operation.  Altogether these energy losses can range from 8% to 20% of the energy output, yielding a round-trip efficiency of 80% to 92% for Li-Ion battery systems.  There are different strategies for managing the cost of the electricity for charging and operating a BESS generator, which depend on the BESS application.

Battery replacements or augmentations are required because lithium-ion battery degradation is an inherent and unavoidable process that impacts the performance and lifespan of stationary energy storage systems (ESS). This degradation manifests primarily as a reduction in the battery’s available energy capacity (MWh) and a corresponding increase in its internal resistance, which can reduce its power output (MW) capability. While some degradation occurs passively due to calendar aging (even when the battery is not in use), the rate of degradation is significantly accelerated by operational factors. A typical degradation rate for a well-managed stationary lithium-ion system can range from 1% to 4% per year of capacity loss depending on usage patterns and environmental conditions. Batteries also age regardless of usage and need to be replaced every 10-20 years.

Several key operational factors influence the rate of lithium-ion battery degradation. Depth of Discharge (DoD) is a crucial factor; deeper and more frequent discharges (e.g., regularly cycling from 100% to 0% state of charge) accelerate degradation much more than shallower cycles (e.g., cycling between 80% and 30%). High charge and discharge rates (C-rates), especially sustained high-power operations, also generate more heat and stress on the battery cells, leading to faster degradation. Operating temperature is another critical environmental factor; extreme temperatures, both hot and cold, negatively impact battery health. High temperatures accelerate chemical reactions within the battery, leading to faster aging and increased risk of thermal runaway, while very low temperatures can cause lithium plating, which reduces capacity and poses safety risks. Maintaining the battery within its optimal temperature range (typically around 20-25°C or 68-77°F) through effective thermal management systems is vital for longevity.

Levelized Cost of Capacity and Levelized Cost of Energy

The Levelized Cost of Capacity (LCOC) for large, stationary Energy Storage Systems (ESS) lands under $100,000 per megawatt per year—significantly lower than that of conventional generator technologies. This cost advantage has made battery energy storage a long-standing solution in Uninterruptible Power Systems (UPS) and is now driving its rapid growth in supporting intermittent renewable generation and managing peak demand. Systems designed to handle short-duration peak loads typically require less energy capacity, resulting in lower Power Capacity costs.  And, when longer-duration storage is needed to meet operational requirements, the effective cost increases proportionally with the duration of energy delivery.

The Levelized Cost of Energy (LCOE) for energy storage varies significantly depending on the duration of the storage (hours of storage), and on the use case (when charged and when discharged). A typical 4-hour system performing a full cycle for 300 days per year and paying $50/MWh for charging will have an LCOE of $133/MWh without incentives.  Figure 7.2 shows that capital costs represent about half of the LCOE, operating costs represent a minor portion (including augmentation). Table 7.1. provides the supporting information for a base case BESS with a 4-hour duration.

Since energy storage is not a producer of energy but rather provides a shift in the time that the energy is used, there is a unique financial term for energy storage called the Levelized Cost of Storage (LCOS).  The LCOS represents  the tolling cost of the system and is equivalent to the LCOE minus the cost of electricity to charge the system. The LCOS for a 4-hr system with 300 cycles per year is about $83/MWh without incentives and about $67/MWh after the ITC incentive is applied.

Energy Storage systems can improve the LCOE and LCOS by performing more cycles per year.  The application determines the frequency of cycles a BESS will discharge per year.

• Low Frequency Cycling:  System discharges to mitigate peaks to reduce demand charges, debottle neck an electric supply network, or reduce the power capacity needed for the primary generator source. This type of operation may cycle an average 2 to 3 times per week.
• Daily Cycling:  System provides pricing arbitrage services and renewable energy shifting. This type of operation may cycle daily, or 5 to 7 times per week.
• Twice-Daily Cycling. System is used to mitigate both an early morning peak and evening peak.  Charges from low-cost grid at night to cover early morning peaks and then charges from solar energy in mid-day to cover the evening peak demand. This type of operation may cycle twice daily, or 10 to 14 times per week.

The Levelized Cost of Energy (LCOE) generally decreases as the number of cycles per week increases.  Figure 7.3 illustrates that a BESS discharging a few times per week to mitigate peaks will have a high LCOE than a BESS that discharges for daily arbitrage.  The lowest LCOE comes from a BESS that can take advantage of cycling twice daily to capture the morning peak and the evening peak.  The analysis incorporates both the rising average cost of input energy associated with more frequent cycling and the higher operating expenses resulting from accelerated battery degradation. Despite these factors, increased cycling still leads to a lower overall LCOE, highlighting the economic advantage of more frequent utilization.

For BESS connected to the grid, the Levelized Cost of Energy (LCOE) varies with its duration rating (hours) as shown in Figure 7.4.  The LCOE initially decreases as the battery duration increases from 0.5 to about 4 hours, at which point it reaches a minimum.  This initial decrease in LCOE is because a longer duration allows for more energy to be sold, increasing revenue for the same power capacity.  Then, as the duration extends beyond the optimal point, the LCOE begins to rise. This increase is due to two main factors: the average cost of purchased electricity for charging rises, and the opportunities for the battery to complete a full charge-discharge cycle decrease. This 4-hour optimal duration is typical for systems operating under standard grid conditions but can change for non-interconnected systems, or special circumstances.