Utilities generate their entire revenue from customers, who represent a load on the system. There are three kinds of load:
- residential, commercial, and industrial customers
- bulk delivery points to reselling utilities
- special-purpose devices such as streetlights and traffic
Demand is the load at the receiving terminals averaged over a specified interval of time. Demand is expressed in real power, apparent power, or current—kilowatts, reactive volt-amperes, volt-amperes, or amperes. Information about the location and size of loads on the system is essential for operations, design, and planning for current and future facilities.