This glossary explains common terms used across Energy Systems Guides. It is intentionally plain-English and reader-focused.
Peak load
The highest demand level over a period, often more important for capacity planning than average use.
Substation
An electrical facility that changes voltage, switches circuits, and supports protection and control.
Storage duration
How long stored energy can serve a load, based on usable energy and demand.
System boundary
The line used to decide what is inside the system being discussed and what is part of the surrounding environment.
Input
A resource, signal, demand, material, person, vehicle, flow, or condition that enters a system.
Output
The result a system produces, such as service, movement, treated water, delivered electricity, repaired equipment, or information.
Feedback loop
Information that returns from the system and helps operators, users, or controls adjust future action.
Capacity
The amount of work, flow, demand, or service a system can handle under stated conditions.
Bottleneck
The limiting point that controls overall flow or performance when demand rises.
Redundancy
Extra capacity, backup equipment, alternate routes, or fallback procedures that reduce reliance on a single point.
Resilience
The ability of a system to absorb disruption, keep essential functions going, recover, and learn.
Maintenance window
A planned period when assets or services may be limited so inspection, repair, updates, or replacement can occur.
Critical asset
An asset whose failure would have unusually high consequences for service, safety, cost, compliance, or recovery time.
Operating margin
The gap between normal demand and the limit where service becomes stressed or unreliable.
Interdependency
A relationship where one system depends on another, such as water systems depending on power or transport systems depending on communications.