Imagine a machine so large and vast in its coverage that it spans the entire United States, stretching from coast to coast, from the northern border with Canada to the southern border with Mexico, criss-crossing and connecting every city, suburb, farm, and mountain range across the country. This hulking machine is not some vision from a sci-fi movie, it is the US electric grid, a complex network of power generation and transmission infrastructure that has been built up and running over the past 100 years. It is a modern marvel, a critical driver of our daily lives, and quite remarkably a largely invisible mystery to many.

Over 500,000 miles of transmission wires and millions of miles of distribution wires span the United States, connecting individual generating units with homes, businesses, and industry.

For comparison, the Interstate Highway System runs slightly less than 50,000 miles. In 2023, the US grid produced over 4 trillion kWh of electricity, with just under 45% coming from natural gas and just over 20% coming from renewable sources. Roughly 1.5 trillion kWh of electricity was used by residential customers alone. In any given hour, the grid carries around 450,000 MWh of electricity.

The US grid is the common name for the tens of thousands of electric power generators and substations, and hundreds of thousands of miles of transmission and distribution lines spread out across the country. This array of wires and machines brings electricity to our homes, schools, businesses, and critical facilities, like hospitals and water supply and wastewater treatment facilities. Take away the grid, and virtually no aspect of our lives would be the same.

Generation: Power Plants

The grid starts at the power plant. Traditionally, power has been generated from coal, gas, or nuclear fuels, or water that has been dammed. In the last three decades, the US has experienced a renewable energy boom, with solar and wind energy increasingly powering more and more of the United States. In coal and gas plants, the fuel is burned to heat up water and create steam, which then turns a turbine, which produces electricity. In a nuclear facility, a fuel rod is used to heat the water and create steam. Wind and hydroelectric energy harness the power of nature (blowing wind or running water) to turn turbines and produce electricity. Solar works a bit differently, by using arrays embedded with a semiconductor (e.g. silicon) to harness the energy transmitted by the sun.

In our region, natural gas is the dominant source of energy. In 2023, it accounted for 49% of New Jersey’s, 46% of New York’s, and 60% of Connecticut’s total electricity generation. Following natural gas, nuclear accounted for 42% of New Jersey’s, 22% of New York’s, and 33% of Connecticut’s total electricity generation. 8% of New Jersey’s total generation came from non-hydroelectric renewable resources, while in New York and Connecticut the share was around 10% and 6%, respectively. New York has some of the highest electricity generation from hydroelectric power plants, accounting for 22% of total electricity generation.

The capacity of power generated at power plants is measured by watts, typically expressed as kilowatt (one thousand watts), megawatt (one million watts), or gigawatts (one billion watts), while the usage or amount of electricity is measured in watt-hours (Wh). For a power plant to be considered ​“utility scale”, meaning it is connected to the larger grid, it has to have a capacity of at least 1 megawatt. The average US home uses nearly 11,000 kilowatt hours (kWh) annually. Within our region, there are nearly 700 power plants, generating anywhere from 1MW of electricity up to over 2,400 MW, with an average capacity of 75 MW. Capacity does not always equal generation, however, as a power plant responds to the needs of the grid. There are also power plants that are only turned on in times of large demand, called peaker plants, that ease the strain on the system, though tend to impact the air quality of the local communities in which they are located.

Transmission: Stepping up voltage and sending electricity across long distances

Once the electricity is generated, it is sent from the power plant to nearby transformers which step up the voltage (a measure of the force of the energy) to a higher level so that it can easily be transmitted over long distances with limited loss. Typically, high-voltage transmission lines span about 300 miles at maximum, and consist of multiple wires for transmission, as well as ground wires, that are all carried by iconic steel towers that connect across the landscape.

Distribution: Stepping down voltage at substations

Transmission lines carry this high-voltage electricity to transformers at substations, which step the power down for local distribution. A substation’s primary role at this level is to convert the high-voltage electricity that was necessary to cross long distances into lower voltage electricity that matches the ​“neighborhood” scale of local power use in homes, businesses, and other infrastructure requiring power.

Distribution: Connecting to homes, businesses, and critical infrastructure

Once electricity reaches distribution lines, it travels either along utility poles or underground trenches to transformers directly on the poles or outside of homes, businesses, and critical facilities powering our lights, appliances, heating and cooling systems, technology, and increasingly, our cars. With the vast system that is the grid, power could be coming from one mile away, to hundreds of miles away.

Such a complex system requires management at multiple levels to ensure that power moves through the grid reliably, safely, and affordably. Common standards enable integration, interconnection, and interoperability throughout the network. The US grid is regulated primarily by the Federal Energy Regulatory Commission (FERC). There are two other regulatory bodies: the North American Reliability Council (NERC), which develops reliability standards, monitors the bulk grid, and educates personnel, and the Institute of Electrical and Electronic Engineers (IEEE), which develops non-mandatory standards for the grid.

The grid itself is broken down into three geographies known as interconnections, or areas where the grids are linked to ensure reliability and safety in the event of power plant or power line failures. Those are the Eastern Interconnection (East of the Rocky Mountains and a small portion of Texas), the Western Interconnection (West of the Rocky Mountains), and the Electric Reliability Council of Texas (ERCOT).

These are then further divided into regional balancing authorities, either Regional Transmission Organizations (RTOs) or Independent System Operators (ISOs). RTOs and ISOs operate and monitor the grid, ensuring a steady power supply by adjusting the amount of electricity transmitted to different locations to meet fluctuating demand. Balancing authorities either operate a traditionally regulated market, where utilities are vertically integrated, or a competitive market, which allows for competition between independent power producers. In traditionally regulated markets, utility companies own the entire supply chain and sell directly to consumers, while in a competitive market, utility companies typically purchase electricity from independent energy producers and then sell it to consumers. Some states with competitive markets allow consumers to pick their preferred source of electricity. New Jersey, New York, and Connecticut all operate under competitive deregulated markets, where customers can either buy power through the default provided by the utility company, or select a third party power provider.

The Federal Energy Regulatory Commission (FERC) oversees the Independent Service Operators in the New York City Metropolitan area. Each state in the region is covered by a separate Independent Service Operator (ISO), non-profit companies that monitor and operate the transmission of electricity in a region and administer the wholesale power market, but do not own the actual transmission infrastructure. ISOs, also known as grid operators or managers, develop forecasts of energy demand for the regions they serve. These forecasts inform generation companies and transmission developers on what the expected future demand and capacity may be, so that they can build new power plants or wires. Any proposed new power plant or other generating unit must first be placed onto an interconnection queue before it can be built and added to the grid. Grid operators use interconnection queues to evaluate projects and determine whether or not they should be added to the grid. Large load projects, such as data centers, generally do not have a formal interconnection queue process, and entering a load interconnection queue is a quicker process than a generator interconnection queue.

Connecticut is within ISO-NE (Independent Service Operator, New England) which covers the grid in New England. Within Connecticut is the Department of Energy and Environmental Protection’s Public Utilities Regulatory Authority (PURA). PURA oversees investor-owned utilities, sets rates, and acts as a ​“quasi-judiciary” on matters regarding utilities. Connecticut has two main utility providers, Eversource and the United Illuminating Company.

New Jersey is within the PJM interconnection, along with thirteen other states stretching from New Jersey to Northern Illinois and Southern Michigan to Virginia, which operates the wholesale market. Utilities in New Jersey are overseen by the New Jersey Board of Public Utilities (NJBPU), which acts as a ​“quasi-judiciary”, similar to Connecticut’s PURA. New Jersey’s electric utility suppliers include Atlantic City Electric, Jersey Central Power and Light, PSEG, and Orange and Rockland Electric Company.

New York has its own Independent Service Operator, the NYISO. NYISO faces a unique challenge in that New York City and Long Island consume the majority of the State’s electricity, which results in transmission constraints and higher prices for downstate residents. Utilities are overseen by the New York Department of Public Services, which also acts as a ​“quasi-judiciary”. There are two state-run power generation companies, New York Power Authority and Long Island Power Authority. New York Power Authority generates and sells electricity and Long Island Power Authority owns and operates the transmission system on Long Island. There are several utility providers in the State, five of which operate in the metropolitan area. They are Consolidated Edison (ConEd), PSEG Long Island, NYSEG, CHG&E, and Orange & Rockland Electric.

Future posts will examine the changes underway in each of the states in our region’s grid areas, as we move toward a more resilient, reliable, and renewable energy system.

Past RPA Works on the Region’s Energy System