Commercial Battery Storage Glossary

AC Coupling refers to connecting solar panels and battery storage through separate inverters—one for the solar PV system and another for the battery—allowing easy retrofit to existing systems. DC Coupling, on the other hand, integrates the solar and battery systems on the same DC bus before a single inverter converts the power to AC, improving efficiency and reducing conversion losses.

An AIO (All-in-One) storage system combines the battery, inverter, BMS, and control interface into a single, compact unit for simplified installation and operation. It reduces compatibility issues and setup time, making it ideal for commercial users seeking a plug-and-play energy storage solution.

Aggregators are intermediary companies in the UK energy market. They act as middle layer between smaller energy systems (like commercial batteries, solar systems, or flexible industrial loads) and the National Grid or energy markets. Since individual sites often aren't big enough, or fast enough, to participate directly, aggregators group them together and manage their performance as one larger, market-ready unit. The aggregator helps everyone in the group make money by using or saving energy at the right times.

An aggregator is not a broker because they don’t just arrange deals between energy buyers and sellers - they actively manage and control energy assets like batteries, solar systems, or flexible loads. They offer technical expertise, trading access, and revenue optimisation for commercial energy users.

Air cooling uses fans or ventilation to remove heat from battery storage systems, helping to keep components at a safe operating temperature. It's a cost-effective and low-maintenance option, though it may be less efficient than liquid cooling in high-temperature or high-power applications.

The refer to international standards (defined by ISO 12944) that classify how resistant materials, like enclosures and components in commercial battery storage systems, are to corrosion under different environmental conditions. In commercial battery storage, choosing the right anti-corrosion grade ensures the enclosure and internal components are protected from rust, moisture, salt, and pollution—especially for outdoor or coastal installations. Higher C-ratings (C4/C5) are often essential for longevity and compliance in exposed or harsh conditions.

Loss of capacity and efficiency over time due to cycling and age. This process leads to a decrease in the battery's capacity and performance, impacting its efficiency and lifespan.

What is BESS? is a solution that stores electricity in rechargeable batteries for later use. In commercial applications, BESS plays a crucial role in helping businesses reduce energy costs, provide backup power, support grid stability, and maximise the use of renewable energy sources like solar or wind. A typical BESS includes the batteries themselves, a power conversion system (inverter), a Battery Management System (BMS) to monitor safety and performance, and often an Energy Management System (EMS) to control when energy should be stored or released, based on current demand, electricity prices, or grid signals.
As renewable energy adoption grows, BESS plays a key role in storing excess solar energy and delivering it when needed.

A physical frame or modular structure used to safely hold and organise multiple battery units within a storage system, making installation, cooling, and maintenance easier.

Behind-the-Meter (BTM) systems are installed on the customer’s side of the utility meter to reduce grid electricity use and manage energy costs. Examples include a business using battery storage to avoid peak charges or pairing solar panels with storage to power operations and provide backup during outages.

Black Start Capability is the ability of a power system—like a battery storage unit—to restart parts of the electrical grid independently after a total or partial shutdown, without relying on external power sources. Battery systems with black start capability can help restore power quickly by energising other grid components or generators during outages.

A Battery Management System (BMS) is a critical component of any battery storage solution, responsible for monitoring and controlling the health, performance, and safety of the battery. It tracks essential parameters such as voltage, current, temperature, and state of charge (SoC) to ensure each cell operates within safe limits. By balancing cells, preventing overcharging, deep discharging, and overheating, the BMS helps extend battery lifespan and prevent failures. In commercial applications, the BMS also communicates with inverters and energy management systems to optimise energy flow, enable remote monitoring, and support services like peak shaving or demand response. This intelligent control makes the BMS essential for reliable, efficient, and safe operation of battery energy storage systems.

It is a hardware component within a Battery Management System (BMS) that monitors individual battery cells or modules. It collects data like voltage, temperature, and current, helps balance the cells, and ensures safe, efficient operation. In larger systems, multiple BMUs can be used to manage different sections of the battery pack,allowing for scalable and reliable system control.

Commercial and Industrial energy storage, refers to battery systems used by businesses to manage energy costs, increase renewable energy consumption, and provide backup power.

measure of how quickly a battery charges or discharges relative to its capacity. For example, a 1C rate means the battery will charge or discharge its full capacity in 1 hour, while 0.5C means it takes 2 hours. It's a key factor in battery performance and system design.

The Capacity Market is a scheme in the UK that helps make sure there’s always enough electricity available, especially during times of high demand. Energy providers, including battery storage systems, get paid to be ready to supply power when the grid needs it. Even if they’re not called on to deliver energy, they still earn money for being available. For businesses with battery storage, this offers a useful way to earn extra income and support the electricity system.

Capital Expenditure - The upfront costs for purchasing and installing battery storage equipment, including hardware and installation. Often, a packaged Battery Energy Storage System (BESS) often includes several items listed below, marked with an asterisk (*).

• Maintenance and servicing (may vary)(*)
• Battery storage units (cells, racks, modules)(*)
• Power Conversion System (PCS) / inverter (*)
• Battery Management System (BMS)(*)
• Energy Management System (EMS) software (may vary)
• Electrical wiring and cabling (may vary)
• Installation costs (labour, equipment hire, civil works)
• Grid connection costs (permits, approvals, fees)
• Protection and safety equipment (e.g., switchgear, fire suppression systems)(*)
• Cooling and HVAC systems (if required)(*)
• Site preparation costs (foundations, enclosures, security)
• Initial warranties and maintenance packages (*)(if purchased upfront)
• Engineering and project management fees

Cell balancing is the process of keeping all battery cells at the same voltage and charge level to ensure safe, efficient performance. Over time, cells can become uneven due to differences in use or manufacturing, which may affect battery life and safety. The Battery Management System (BMS) handles this by using passive or active methods to balance the cells and protect the system.

Speed at which a battery charges, measured in kW or C-rate.

It involves safely starting up and testing a battery energy storage system to ensure it operates correctly and meets design specifications. This process includes checking connections, verifying software and communication, calibrating sensors, and performing initial charge/discharge cycles. It confirms the system is ready for operation, meets safety standards, and can deliver expected performance before being integrated into a commercial setup or the grid.

Curtailment refers to the intentional reduction of electricity generation from renewable sources when supply exceeds demand or the grid cannot accept more power. It helps maintain grid stability but can lead to lost revenue for generators unless mitigated by storage or other solutions.

A battery cycle refers to one full charge and discharge equivalent - meaning the battery has delivered and then been recharged with energy equal to 100% of its capacity, though not necessarily in one go. For example, discharging 50% one day and another 50% the next, followed by a full recharge, would also count as one full cycle. A battery’s lifespan is often measured in the number of cycles it can perform before its capacity significantly degrades.

Battery cycle life refers to the number of times a battery can be fully charged and discharged before its capacity degrades to a certain level, usually 80% of its original capacity. It indicates how many charge/discharge cycles a battery can support before significant performance loss occurs. For commercial battery storage systems, the average cycle life for Lithium Iron Phosphate (LiFePO₄) batteries typically ranges from 6,000 to 10,000 cycles at 80% Depth of Discharge (DoD).

Depth of Discharge (DoD) is a measure of how much energy is taken out of a battery during a discharge cycle, expressed as a percentage of its total capacity. For example, using 80 kWh from a 100 kWh battery equals 80% DoD. Higher DoD allows more usable energy but may shorten battery life.

Speed of energy release from a battery. Discharge rate can be measured in kW or C-rate, depending on whether the focus is on absolute power output (kW) or the relative speed of discharge (C-rate).

A Distribution Network Operator (DNO) in the UK is a licensed company that manages and maintains the local electricity network, delivering power from the national grid to homes and businesses. DNOs are responsible for the safe and reliable operation of infrastructure such as cables, poles, and substations. Unlike energy suppliers, they don’t sell electricity but handle key services like new connections, network upgrades, and repairing faults.

A DNO (Distribution Network Operator) notification is a formal submission to the local electricity network operator when installing or modifying energy systems that connect to the grid, such as solar panels, battery storage, or EV chargers. This notification ensures the grid can handle the additional load or export capacity and that the installation meets safety and regulatory standards.

DSR in the UK refers to the process where energy users, such as households or businesses, adjust their electricity usage in response to signals or financial incentives, usually to help balance supply and demand on the electricity grid.

Fast-acting grid service in the UK designed to keep electricity frequency close to 50 Hz. It relies on assets like commercial battery storage systems that can respond within less than one second to sudden frequency changes, either by absorbing or supplying power instantly.
DC is one of National Grid ESO’s highest-value frequency response services. Commercial battery systems providing this service are paid for rapid, accurate action based on grid conditions. Their ability to react in milliseconds helps prevent blackouts and stabilise the system, making DC ideal for advanced, high-speed technologies like battery storage.

Everyday support - a fast-response service but is designed to manage slightly larger, routine frequency fluctuations with more flexible accuracy requirements. DM provides broader support and allows more assets to participate, even those that don’t meet DR’s high precision thresholds. Together, both services help keep the grid stable during normal conditions.

It's not an emergency response like Dynamic Containment, but still provides precise, continuous control of grid frequency. DR corrects even the smallest deviations in real time, requiring assets like commercial battery storage systems to deliver instant and continuous highly accurate responses.

Central control platform that monitors, manages, and optimises energy use, generation, and storage across a commercial site. In battery storage systems, the EMS determines when to charge or discharge the battery based on factors like demand, electricity pricing, solar generation, and grid signals.
Working alongside the EMS is the Battery Management System (BMS), which focuses specifically on the health and safety of the battery. While the EMS manages strategy and energy flow across the system, the BMS ensures the battery operates safely and reliably. Together, they form the backbone of intelligent and efficient battery storage operations.

Refers to the strategy of purchasing electricity when prices are low (typically during off-peak hours) and storing it for use or sale when prices rise (usually during peak demand). This approach helps reduce energy costs, generate revenue, and improve grid efficiency, particularly in markets with variable pricing or time-of-use tariffs.

In simple terms, energy density in solar batteries means how much energy a battery can store compared to its size or weight. It’s usually measured in watt-hours per litre (Wh/L) or per kilogram (Wh/kg), and helps show how compact or heavy a battery needs to be to store a certain amount of energy.

Selling and buying electricity stored in the battery on the UK’s wholesale markets (e.g., via platforms like EPEX Spot or Nord Pool) for profit.

Safety feature designed to detect and automatically control or extinguish fires within a battery storage system. These systems often include sensors, alarms, and fire-suppressing agents such as clean gases, aerosols, or dry chemicals that activate in the event of overheating, smoke, or flames. In commercial battery storage, a fire suppression system is critical for protecting equipment, ensuring safety, and complying with regulations. It helps minimise damage, reduce downtime, and provide peace of mind, especially in enclosed spaces or high-risk environments.

A service that helps keep the electricity grid stable at its target frequency of 50 Hz. When there’s a sudden change in supply or demand, the frequency can shift—too high or too low—which can cause equipment damage or even outages. Commercial battery storage systems are well-suited for frequency response because they can react almost instantly, charging or discharging within seconds to help stabilise the grid.
In the UK, this service is part of Dynamic Services (e.g. Dynamic Containment, Dynamic Regulation, and Dynamic Moderation) launched by National Grid ESO to replace older, less responsive schemes like Firm Frequency Response (FFR).By participating in these services, battery operators can earn revenue while supporting grid stability, making frequency response a key part of the stacked revenue model for commercial energy storage in the UK.

Maximum amount of electricity a site can import or export the grid, as agreed with the local network operator. These limits help keep the grid safe and balanced. In commercial battery storage, batteries can help stay within these limits by storing extra energy or supplying power when needed. This avoids extra charges or problems with the grid connection.

Balancing services help keep the UK electricity grid stable by making sure supply and demand stay in balance, especially around the target frequency of 50 Hz. This is important for keeping power reliable across the country.
To do this, National Grid ESO pays businesses—like those with commercial battery storage or large energy use—to quickly change how much power they use or produce when the grid needs help. The faster they respond, the more they can earn. Smart technology is key to taking part, as it can react quickly and safely without affecting daily operations.

A hybrid cooling system in battery storage combines two or more cooling methods—typically air and liquid cooling—to regulate battery temperature more effectively. This approach takes advantage of the simplicity and cost-effectiveness of air cooling along with the efficiency and precision of liquid cooling, especially in high-density or high-power applications. It’s commonly used in commercial and utility-scale battery installations where temperature control is critical.

indicates how well electrical equipment, such as commercial battery storage systems, is protected against the intrusion of solid objects (like dust) and liquids (like water). The rating consists of two digits: the first relates to solid particle protection (rated 0–6), and the second to liquid ingress protection (rated 0–9). For example, an IP65 rating means the enclosure is dust-tight and protected against low-pressure water jets from any direction.
In commercial battery storage, a high IP rating is important for ensuring safety, reliability, and longevity—especially in outdoor or industrial environments. Choosing equipment with an appropriate IP rating helps protect against weather, dirt, and accidental splashes, reducing the risk of system failure and maintenance costs.

Islanding detection is a safety feature in grid-connected systems like solar panels or batteries that checks if the system gets cut off from the main grid but keeps running. If this happens, it could be dangerous for utility workers and equipment. Islanding detection makes sure the system shuts down or switches to backup mode when the grid goes down, so power isn’t sent back into the grid by mistake. It’s an important part of staying safe and meeting grid rules.

It is a unit of energy that measures how much electricity is used or stored over time. It represents using 1 kilowatt of power for 1 hour. So, for example, 1,000-watt device running for one hour uses 1 kWh of energy.

LCOE measures the average cost to generate one kilowatt-hour (kWh) of electricity over the lifetime of a power-generating system, such as a solar PV array. It includes capital costs, operation and maintenance (O&M), fuel (if applicable), and total expected energy output. In commercial battery storage projects, LCOE helps compare generation technologies and assess project viability.
It also represents the long-term breakeven price a project must earn per kWh to recover all costs and meet its required rate of return. It's a key metric for both technical and financial decision-making.

LCOS is the average cost to store and discharge 1 kWh of electricity from a battery over its usable life. It accounts for capital costs, operations and maintenance (O&M), efficiency losses, and degradation. Similar to LCOE (Levelised Cost of Energy), LCOS focuses specifically on energy storage, measuring the true cost of storing and delivering electricity through the system.

type of lithium-ion (Li-ion) battery known for its excellent safety, thermal stability, long cycle life, and low cost per cycle. Although it has lower energy density compared to other Li-ion chemistries, its durability and reliability make it ideal for commercial energy storage systems and electric buses.

Liquid cooling is a method of managing battery temperature by circulating a coolant—such as water or a special fluid—near the battery cells. It removes heat more efficiently than air cooling, offering better temperature control and helping extend battery life and performance. This system is often used in high-power or high-density commercial and EV battery applications.

Is a type of rechargeable battery widely used in commercial energy storage due to its high energy density, efficiency, and long cycle life. It comes in several chemistries, with LFP (Lithium Iron Phosphate) being one of the most popular for commercial applications.

Other types of Lithium-Ion battery chemistries:

• NMC (Nickel Manganese Cobalt Oxide) – High energy density and good overall performance. Common in EVs and compact storage systems.
• NCA (Nickel Cobalt Aluminum Oxide) – Very high energy density and long life, but more expensive and less thermally stable. Used in high-performance EVs.
• LCO (Lithium Cobalt Oxide) – High energy density but shorter lifespan and safety concerns. Mostly used in consumer electronics.
• LMO (Lithium Manganese Oxide) – Good safety and thermal stability, with moderate performance. Found in power tools and some EVs.

It involves using batteries to move electricity consumption from times of high demand and high prices to periods of lower demand and cheaper electricity. This is achieved by charging the batteries during off-peak hours when electricity rates are low and discharging them during peak hours when prices rise or grid demand increases.

Digital do-it-yourself tool or digital interface that connects commercial battery storage systems to energy markets. It allows businesses to automatically buy, sell, or shift electricity based on real-time prices, grid needs, or service opportunities. In short, it acts as a smart bridge between a battery system and the energy market, helping businesses earn revenue and optimise performance. As a side note, aggregators may rely on Market Access Platforms to operate battery systems and engage with energy markets on behalf of their clients.

Battery role in stabilising or islanding local energy systems.

Maximum amount of power or energy a battery system is rated to deliver under ideal, lab conditions when new. It represents the full rated capacity set by the manufacturer, but actual usable capacity is often lower due to safety margins, degradation, and real-world operating conditions. Nameplate Capacity, Nominal Capacity, and Total Capacity are often used interchangeably.

Office of Gas and Electricity Markets - the governing body that set the standards by which all DNO's in the UK operate.

Operational Expenditure - Regular operational costs such as maintenance, insurance, management software, and ongoing grid connection fees. For commercial battery storage, OpEx typically includes:

• Maintenance and servicing
• Insurance
• Software subscriptions
• Grid connection charges
• Monitoring and management

Management of individual battery packs within a larger system to improve performance, efficiency, and lifespan. It involves balancing charge/discharge, monitoring temperature, and adjusting use per pack to prevent weak points, extend battery life, and ensure safe, reliable operation.

a time-based metric that shows how long it takes to recover the initial investment through savings or revenue. In other words, it's the amount of time needed to break even on a project like commercial battery storage.

Inverter system that converts DC from batteries to usable AC. A PCS is a two-way inverter system designed for bidirectional power flow, allowing both charging and discharging. It’s a key part of commercial energy storage systems, enabling full integration with the grid and other energy sources. A PCS contains an inverter, but it does more than just invert power. It typically includes converters (inverters and rectifiers), control systems, and sometimes transformers and switchgear.

Commercial energy management strategy that sets a predefined maximum limit on electricity demand during peak periods. When usage approaches this cap, the system automatically takes action, such as discharging batteries or curtailing non-essential loads, regardless of energy prices. This helps businesses avoid high peak demand charges, reduce strain on electrical infrastructure, and stay within contractual or technical limits.

Also known as peak load shaving, is a demand-side strategy used to reduce electricity use during high-demand periods. It helps flatten the demand curve, making the grid more stable and lowering energy costs for users. It reduces peak demand only when needed, based on real-time usage or pricing. The goal is to reduce peaks without setting a fixed limit.

Power output per unit volume or mass. Power Density refers to the amount of power a battery system can deliver relative to its size or weight, typically measured in watts per litre (W/L) or watts per kilogram (W/kg). In commercial battery storage, high power density means more power can be delivered from a smaller or lighter system, which is important for space-constrained sites or applications requiring fast energy discharge, such as grid support or backup power.

Revenue Stack refers to the combination of different income streams a commercial battery storage system can generate. Instead of relying on a single use case, such as backup power or peak shaving, the system earns from multiple services—like energy arbitrage, grid balancing, demand response, and capacity markets. This stacked approach maximises the financial return on the battery investment and improves overall system utilisation.

A profit-based metric that shows, as a percentage, how much return or profit you earn on your initial investment. It reflects how profitable the investment is overall, helping businesses assess the financial performance of systems like commercial battery storage.

Percentage of energy retained after charging and discharging. For example, if you put in 100 kWh and get back 90 kWh, the RTE is 90%. In commercial battery storage, a high RTE means lower energy losses and better system performance, directly affecting cost savings and return on investment.

Self-Consumption is using electricity generated on-site directly within the property instead of exporting it to the grid. In commercial setups, batteries help store excess energy for later use, reducing grid reliance and cutting costs.

Loss of charge while the battery is not in active use. In commercial battery storage, this gradual energy loss affects long-term efficiency and is influenced by factors like battery type, temperature, and age. Commercial systems typically use battery chemistries with low self-discharge rates (like lithium-ion) and include battery management systems (BMS) to monitor and minimise these losses.

It refers to the pattern of energy consumption (usually electricity) over a specific period for a particular location or site. It helps identify patterns in energy consumption, such as peak demand periods and base loads. In commercial battery storage, analysing the site load profile is essential for system sizing, optimising battery use, and planning strategies like peak shaving, load shifting, or time-of-use savings.

Battery systems integrated with smart grid technology to store, manage, and distribute energy more efficiently. These systems use advanced controls and communication tools to respond in real time to grid demands, helping balance supply and demand, support renewable integration, and improve grid stability. In commercial settings, it enables participation in energy markets, peak shaving, and grid services, while enhancing energy resilience and efficiency.

A gradual mismatch between a battery's actual charge and the reported State of Charge (SoC). It occurs over time due to small measurement errors and can impact system performance. Commercial systems correct it through periodic recalibration.

Soft Cap is a recommended limit set by the battery management system (BMS) to guide safe and efficient operation, such as for charge level, temperature, or power output. Unlike a hard cap, a soft cap can be temporarily exceeded, but doing so may reduce battery life or performance. It acts as a buffer to help protect the system while allowing flexibility when needed.
Hard Cap is an absolute limit that the system will not exceed. Crossing it could pose safety risks or cause damage.

Optimising battery returns by combining multiple services and use cases. Commonly used in commercial battery systems, maximises returns by combining multiple services—such as peak shaving, energy arbitrage, grid services, and backup power. This approach allows businesses to generate income from different sources at the same time, increasing overall revenue and improving the value of their battery investment.

It is the battery’s current charge level, expressed as a percentage of its total capacity. For example, 100% means fully charged, while 0% means empty. In commercial battery systems, SoC is essential for tracking available energy, protecting battery health, and optimising system performance.

It indicates the actual amount of energy stored in a battery at a given time, typically measured in kilowatt-hours (kWh) or megawatt-hours (MWh). Unlike State of Charge (SoC), which is a percentage, SoE shows the usable energy in absolute terms.

It measures the overall condition of a battery compared to when it was new. It’s usually expressed as a percentage, where 100% means the battery is performing like new. Over time, as the battery ages and undergoes charging cycles, its capacity and efficiency decline, lowering the SoH. In commercial battery systems, tracking SoH is crucial for maintenance planning, performance optimisation, and determining when a battery may need servicing or replacement. This can be done through a combination of monitoring, diagnostics, and data analysis. In modern commercial systems, SoH is usually reported automatically by the BMS and displayed on dashboards for facility managers or operators.

It shows how much an electrical signal is distorted by extra waveforms called harmonics. In commercial battery systems, keeping THD low is important to protect equipment, reduce energy loss, and ensure smooth operation. Excessive THD can cause serious issues like transformer inefficiency and communication interference, overheating, and poor performance. Modern commercial inverters often keep THD below 3%, or even 1%, to meet strict grid and performance standards.

Overall strategy for controlling battery temperature. In commercial setups, this often includes active cooling, ventilation, and monitoring systems.

A dangerous condition in batteries where rising temperatures cause a self-sustaining reaction, leading to overheating, fire, or explosion. It can be triggered by damage, overcharging, or internal faults. In commercial battery systems, robust thermal management and safety features are critical to prevent thermal runaway and ensure safe operation.

In the context of battery storage, "throughput" refers to the total amount of energy a battery can store and deliver over its lifetime, typically measured in megawatt-hours (kWh or MWh). It represents the battery's ability to undergo charge and discharge cycles without significant performance degradation. It’s a key indicator of battery performance and longevity, especially for commercial systems where frequent cycling impacts both warranty and return on investment.

Time-of-Use (ToU) is a pricing model where electricity rates change throughout the day. Commercial battery systems use ToU to save money by charging during low-cost periods and discharging when prices are high.

Unbalanced Loads Operation (100%) refers to a battery inverter or energy system's ability to supply full power to loads even when electrical demand is uneven across phases. In three-phase commercial systems, such imbalance is common. A system with 100% unbalanced load operation can handle this without performance loss, ensuring reliable power delivery and efficient energy use—a crucial capability for maintaining stability and performance in real-world conditions.

Usable Capacity is the amount of a battery's total storage that can be actively used for charging and discharging in real-world operation. It’s usually slightly less than the total capacity to protect battery health and safe operation. It defines how much energy is available to support the grid, reduce peak demand, or lower energy costs.

A Virtual Power Plant (VPP) is a network of decentralised energy resources—ranging from small to medium-scale generators, flexible consumers, and storage systems—coordinated through software to act as one power plant. Unlike a traditional power plant that exists in a single physical location, a VPP is distributed across multiple locations. While VPPs often include medium-scale assets like commercial batteries, they are not limited to this size and can also aggregate residential or larger-scale systems.