Grid Glossary

TRENDING TERM

Critical Issue Fast Path (CIFP)

An accelerated stakeholder process used in PJM Interconnection to resolve urgent, contentious, and time-sensitive issues that cannot be resolved through the normal stakeholder process. The process involves several stages of discussion and proposal development, culminating in a submission to the Federal Energy Regulatory Commission (FERC) for approval. The CIFP process has been used in recent years to discuss large load additions (2025) and resource adequacy (2023).

TRENDING TERM

Effective Load Carrying Capability (ELCC)

Measurement used to calculate how much an energy resource–such as a wind farm or solar array–contributes to the overall reliability of the grid. It assesses the resource’s ability to meet electricity demand, particularly during peak usage periods, and is especially useful for variable renewable energy sources whose output depends on factors like weather conditions. 

TRENDING TERM

Disturbance

Refers to any unwanted or unplanned electrical event that interferes with the normal operation of the electrical grid. These can manifest in power outages, surges, and other events, and can originate from various sources within the electrical grid, such as loss of a large generating unit or another grid asset, such as a transmission line or transformer.

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Baseload

The minimum amount of electricity that a utility must provide to meet the consistent, ongoing needs of its customers. Historically, this steady demand was met by large power plants (like coal or nuclear) that ran continuously. Today, with more renewable energy, this minimum demand can be met by a flexible mix of various power sources, rather than relying solely on specific “baseload plants”.

  • Baseload capacity:  The generating equipment normally operated to serve loads on an around-the-clock basis.
  • Baseload plant:  A plant, usually housing high-efficiency steam-electric units, which produces electricity at an essentially constant rate and runs continuously. 
Battery Energy Storage System (BESS)

A technology that stores electrical energy in rechargeable batteries for later use. Batteries help stabilize the grid, manage energy demand, and increase the use of renewable energy.

Behind-the-meter

Any energy resource that provides energy directly to a home or business without passing through a utility company’s meter. Examples include rooftop solar and microgrids.

Hydrogen

Fuel cell that carries energy generated from another source. It can be used in fuel cells to generate electricity with water as the only byproduct, or it can be burned for heat. Hydrogen can be produced from a variety of sources–renewable energy such as solar or wind, or gas plants, nuclear, and other energy sources–which dictate whether it can be considered “clean” or not.

Independent Market Monitor (IMM)

An entity that is hired by an Independent System Operator (ISO) or Regional Transmission Organization (RTO) to oversee and assess the operations of the wholesale electricity market. Its primary role is to ensure fair and competitive market practices by monitoring market participant behavior and identifying potential market manipulation or design flaws.

Independent System Operator (ISO)

A non-profit organization that manages the electricity grid and wholesale electricity markets within a specific geographic region. Its primary role is to ensure the reliable and efficient delivery of electricity, balancing supply and demand in real-time and overseeing fair competition among market participants. 

  • List of ISOs and RTOs:
    • CAISO – California ISO
    • NYISO – New York ISO
    • Electric Reliability Council of Texas (ERCOT); also a Regional Reliability Council
    • MISO – Midcontinent Independent System Operator, serves northern Midwest, southeast, and parts of Canada
    • ISO-NE – ISO New England
    • SPP – Southwest Power Pool
    • PJM – Pennsylvania-New Jersey-Maryland Interconnection- services 13 states in Midatlantic and Midwest region
Inertia

In the context of the grid, it refers to the energy stored in the rotating machinery of generators, such as the turbines of a gas plant or hydropower station. 

The turbines rotate at the same rate as the grid–60 cycles per second (hertz) in the United States–and help provide stability for the grid, particularly during spikes in power demand or other disturbances. If the power plant goes offline for any reason, the inertia of the turbines maintains the grid’s frequency for a window of time while another power source is brought online to replace the offline generator. 

Certain types of renewable energy, such as wind and solar photovoltaic, do not use rotational generators, instead using electronic inverters. But these renewable technologies include electronic sensors that can respond to changes in frequency quickly, and can replace the need for rotational inertia.Synthetic inertia – Inertia provided without synchronous generators and refers to the transfer of active power into the grid from a grid-forming inverter. This type of inertia can provide the same, or even better, stabilization services as traditional inertia because it has an instantaneous effect.

Interconnection

The process of connecting new power sources, like renewable energy generators or energy storage systems, to the existing grid infrastructure. It involves integrating these new sources with the grid’s transmission and distribution networks, ensuring a stable and reliable flow of electricity.

Interconnection queue

The line in which power generation and transmission projects must wait after they have requested to connect to the electric grid. These queues are managed by grid operators like ISOs (Independent System Operators) or RTOs (Regional Transmission Organizations). Projects are evaluated for their impact on the grid and the necessary upgrades before they can connect and deliver electricity.

Intermittent power

A power source whose availability and output fluctuate due to natural variations in its energy source. This means the power supply isn’t consistently available, often linked to weather conditions like wind speed, time of day, or season. Renewable energy output can be forecast and stored in battery systems to maintain grid reliability.

Inverter

Technology that provides the interface between the grid and energy sources like solar panels, wind turbines, and energy storage, converting direct current to alternating current (which is how electricity is delivered in the United States). It is used to convert power output from solar cells, batteries, and wind turbines into power that can be injected into the grid.

Inverter-Based Resources (IBR)

A power generation or storage device (such as a battery) that connects to the electrical grid through an inverter, a power electronic device that converts direct current (DC) to alternating current (AC). These resources, including solar photovoltaic (PV) systems, wind turbines, and battery energy storage systems, are increasingly important for grid stability.

ISO-NE

ISO New England

National Association of Regulatory Utility Commissioners (NARUC)

A non-profit organization that represents state public service commissions, which regulate essential utility services like energy, telecommunications, and water. Its stated aim is to improve the quality and effectiveness of public utility regulation. It has eight committees:

  1. Consumer Affairs
  2. Critical Infrastructure
  3. Electricity
  4. Energy Resources & Environment
  5. Gas
  6. International Relations
  7. Telecommunications
  8. Water

It also has a task force focused on Innovation.

NERC

Non-profit organization that operates to assure the effective and efficient reduction of risks to the reliability and security of the grid. It oversees six regional reliability entities and encompasses all of the interconnected power systems of Canada and the contiguous United States, as well as a portion of the Mexican state of Baja California. Its responsibilities include working with all stakeholders to develop standards for power system operation, monitoring and enforcing compliance with those standards, assessing resource adequacy, and providing educational and training resources as part of an accreditation program. NERC also investigates and analyzes the causes of significant power system disturbances in order to help prevent future events and produces reports about the near and long-term reliability forecast.

Notice of Proposed Rulemaking (NOPR)

A document used by government agencies to announce a potential new rule or amendment to an existing one. This is an official part of the law-making process, allowing public comment before the rule is finalized. The acronym is frequently used by the Federal Energy Regulatory Commission (FERC).

NREL

A government-owned, contractor-operated facility, funded and overseen by the United States Department of Energy’s (DOE) Office of Energy Efficiency and Renewable Energy (EERE). It specializes in the research and development of renewable energy, energy efficiency, energy systems integration, and sustainable transportation.

NYISO

New York ISO

Queue

(see: Interconnection Queue)

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