Download Free (.pdf)State of Health
A measure of how much usable capacity a battery retains compared to its original condition. It reflects age, temperature history, and cycling behavior. A declining value indicates reduced available energy.
State of Charge
The percentage of energy currently stored in the battery relative to its full capacity. It determines whether the system can charge or discharge. SOC limits protect battery health and ensure safe operation.
Round-Trip Efficiency
The percentage of energy retained after charging and discharging a battery, accounting for conversion and thermal losses.
Resiliency
A facility’s ability to continue powering essential loads during a utility outage. It is typically enabled through energy storage or other on-site resources that isolate and serve critical circuits when the grid fails. A resilient system ensures safety, business continuity, and operational stability by keeping priority equipment running through extended interruptions.
Metering Mode
A non-dispatch mode where the system is installed for monitoring only and not for active battery control. It records performance, load, and electrical data without issuing charge or discharge commands, allowing another platform or external system to manage dispatch if needed. This mode supports reporting, visibility, and diagnostics without influencing site operation.
Island Mode/Islanding
A mode of operation where a site electrically isolates itself from the utility grid and operates independently using on-site generation and storage
Import Limit
The maximum power a facility is permitted to draw from the grid at any moment. Storage or on-site generation may be used to stay below this value. These limits help prevent overloading utility or facility infrastructure.
Front-of-the-Meter
Energy storage systems that interconnect on the utility side of the service point rather than the customer side. Because they operate as grid-facing assets, they rely on revenue-generating programs such as wholesale market participation, grid services, demand response, or DC clipping recapture from large solar sites, rather than behind-the-meter bill savings.
Energy Storage System
A collection of components that stores energy and releases it as electrical power when needed. Technologies include lithium-ion, flow batteries, lead-acid, mechanical storage, and thermal storage. Commercial ESS installations typically include batteries, inverters, and controls.
DC-Coupled
A DC-coupled system connects the PV array and energy storage to a shared DC bus through a hybrid inverter. This setup enables direct PV-to-battery charging and can improve system efficiency, making it a popular choice for integrated solar-plus-storage designs
Critical Load Panel
An electrical subpanel that serves only essential equipment during outages. Energy storage systems often prioritize these circuits when operating in islanded mode.
C-Rate
A measure of how quickly a battery is charged or discharged relative to its capacity (e.g., 1C = full discharge in one hour).