Applications in the Bulk Generation domain are typically the first process in the delivery of electricity to customers. Electricity generation is the process of creating electricity from other forms of energy, which may vary from chemical combustion to nuclear fission, flowing water, wind, solar radiation and geothermal heat.
The Bulk Generation domain is electrically connected to the Operations, Markets and Transmission domains. Some benefits to the Bulk Generation domain from the deployment of the smart grid are the ability to automatically reroute power flow from other parts of the grid when generators fail.
Actors in the Bulk Generation domain may include generators of electricity in bulk quantities, as well as storage devices that can store energy for later distribution.

Transmission is the bulk transfer of electrical power from generation sources to distribution through multiple substations. The Transmission domain is electrically connected to the Bulk Generation and Distribution domains, as well as communicating with the Operations, and Markets domains.
A transmission network is typically operated by a Regional Transmission Operator or Independent System Operator (RTO/ISO) whose primary responsibility is to maintain stability on the electric grid by balancing generation (supply) with load (demand) across the transmission network.
The Transmission domain may contain distributed energy resources such as electrical storage or peaking generation units. Energy and supporting ancillary services (capacity that can be dispatched when needed) are procured through the Markets domain and scheduled and operated from the Operations domain. They are then delivered through the Transmission domain to the utility-controlled distribution system and finally to customers.
Actors in the transmission domain may include remote terminal units, substation meters, protection relays, power quality monitors, phasor measurement units, sag monitors, fault recorders, and substation user interfaces.

The Distribution domain is electrically connected between the Transmission domain and the Customer domain at the metering points for consumption. The Distribution domain also communicates with the Operations and Markets domains.
Historically distribution networks have little instrumentation installed, and there was very little communications within this domain that was not manually done by humans. Many communications interfaces within this domain were hierarchical and unidirectional.
With the advancement of distributed storage, distributed generation, demand response and load control, the ability of the Customer domain to improve the reliability of the Distribution domain exists. Distribution networks are now being built with much interconnection, extensive monitoring and control devices, and distributed energy resources capable of storing and generating power. Such distribution networks may be able to break into self-supporting "micro-grids" when a problem occurs and customers may not even be aware of it.
Actors in the Distribution domain may include capacitor banks, sectionalizers, reclosers, protection relays, storage devices, and distributed generators.

The Customer domain is electrically connected to the Distribution domain. It communicates with the Distribution, Operations, Markets, and Service Provider domains.
Actors in the Customer domain typically enable customers to manage their energy usage and generation. These actors also provide control and information flow between the Customer and the other domains. The boundaries of the Customer domain are typically considered to be the utility meter and/or an additional communication gateway to the utility at the premises.
There are three types of customers within the Customer domain: industrial, commercial/building, and home. The limits of these domains are typically set at less than 20kW of demand for Home, 20-200kW for Commercial/Building, and over 200kW for Industrial. The electric vehicle is an example of an actor that interfaces with all three domains.
All three domains (industrial, commercial and residential) have a meter actor and a gateway that may reside in the meter or may be an independent actor. The gateway is the primary communications interface to the Customer domains. It may communicate with other domains via AMI or another method such as the Internet. It typically communicates to devices within the customer premises using a home area network or other local area network. The gateway enables applications such as remote load control, monitoring and control of distributed generation, in-home display of customer usage, reading of non-energy meters, and integration with building management systems. It may also provide auditing/logging for security purposes.

Actors in the Operations domain perform the ongoing management functions necessary for the smooth operation of the power system. While the majority of these functions are typically the responsibility of a regulated utility, many of them may be outsourced to service providers and some may evolve over time. For instance, it is common for some customer service functions to be part of the Service Provider domain or Markets domains.
The typical applications performed within the Operations domain may include: network operation, network operation monitoring, network control, fault management, operation feedback analysis, operational statistics and reporting, real-time network calculation, dispatcher training.

Actors in the Markets domain typically perform pricing or balance supply and demand within the power system. The boundaries of the Markets domain are typically considered to be at the edge of the Operations domain where control happens, and at the domains containing physical assets (e.g. generation, transmission, etc).
The interfaces between the Markets domain and those domains containing generation are most critical because efficient matching of production with consumption relies on markets. Besides the Bulk Generation domain, electricity generation also takes place in the Transmission, Distribution, and Customer domains and is known as distributed energy resources (DER). NERC CIPs consider suppliers of more than 300 megawatts to be Bulk Generation; most DER is smaller and is typically served through aggregators. DERs participate in markets to some extent today, and will participate to a greater extent as the smart grid becomes more interactive.

Actors in the Service Provider domain include the organizations providing services to electrical customers and utilities. That is, the actors in this domain typically perform a variety of functions that support the business processes of power system producers, distributors and customers. These business processes range from traditional core services such as billing and customer account management to enhanced customer services such as home energy generation and management. It is expected that service providers will create new and innovative services (and products) in response to market needs and requirements as the smart grid evolves. These emerging services represent an area of significant economic growth. Services may be performed by the electric service provider, by a third party on their behalf, or in support of new services outside of the current business models.
The boundaries of the Service Provider domain are typically considered to be the power transmission and distribution network controlled by the Operations domain. Services provided must not compromise the security, reliability, stability, integrity and safety of the electrical power network.
The Service Provider domain is typically electrically connected at the Customer domain. It communicates with the Markets, Operations and Customer domains. Of these, the interfaces to the Operations domain are critical for system control and situational awareness but the interfaces to the Markets and Customer domains are critical for enabling economic growth through the development of "smart" services. The Service Provider domain may, as an example, provide the "front-end" connection between the customer and the market(s).