Electricity is produced in New England by more than 350 generating resources—natural gas and oil-fired power plants, hydroelectric dams, coal or nuclear stations, biomass plants, among others. Generators sell the electricity through either the region's wholesale electricity markets or contracts with utilities and competitive suppliers.
ISO New England dispatches and directs the flow of electricity from generators through New England's 8,000 miles of high-voltage transmission lines to substations, where it is "stepped down" in voltage to feed into local distribution lines.
Electric utilities and competitive suppliers buy electricity either through the ISO-run wholesale markets or contracts with power producers; local utilities distribute the electricity to businesses and homes.
The region's 6.5 million households and businesses create the demand for electricity, which must be produced the instant it is needed.
ISO New England's overview brochure [PDF] further describes the ISO's role in operating New England's bulk electric power system and administering the region's wholesale electricity markets.