How Electricity is Delivered
The vast majority of Massachusetts electricity is produced at large, central electric facilities scattered around the state and region. The power from these facilities travels over the electric grid - a complex web of power lines - to individual customers. Understanding how the electric grid works in important in understanding how clean energy is connected to individual customer locations.
The Electricity Grid
The grid can most easily be understood as a web between power plants and the consumer of electricity. This web includes the power plants, the transmission substations, high voltage transmission lines, substations, and the consumer.
First, a power plant generates electricity. That electricity then goes to a transmission substation where it passes through a transformer to increase the voltage. This transformation is made to allow the electricity to travel quickly and efficiently along the transmission lines.
The electricity then travels at high speed along the high-voltage transmission lines to a power substation. Here, the electricity passes through another transformer to reduce the voltage so the electricity is in a usable form for consumers. Electricity may pass through several transformers before it can be used by consumers. In addition to the transmission station and the substation, smaller transformers are used nearer to the electricity's end use. You can see these in the form of canisters on utility poles near homes or business, or in the form of large green boxes in front of office complexes or residential developments.
The pathway from a power station to the consumer is a small portion of the electricity grid in Massachusetts. The grid is made up of hundreds of interconnected pathways. In fact, the grid in Massachusetts is connected to other power stations and transmission lines in the other New England states, as well as New York and Canada. These are the major transmission systems in the region:
BHE - |
Northeast Maine |
WMA - |
Western Massachusetts |
ME - |
Western & Central Maine/ |
SEMA - |
Southeast Massachusetts/ |
SME - |
Southeast Maine |
RI - |
Rhode Island/bordering MA |
NH - |
North, East, & Central |
CT - |
North and East Connecticut |
VT - |
Vermont/Southwest New Hampshire |
SWCT - |
South Central Connecticut |
BOSTON - |
Greater Boston, inc. North Shore |
NOR - |
Norwalk/Stamford, Connecticut |
CMA/NEMA - |
Central Massachusetts / |
NB, HQ and NY - |
Represent the New Brunswick , |
Information courtesy of ISO New England RTEP Executive Summary and Overview, 2003
The New England grid is in turn connected to other regional grids that link across the country. High-voltage transmission lines form and interconnect the nation's regional grids. As a whole, these lines comprise the National Power Grid which, on a federal level, is divided into three macro-grids known as the Western, Eastern, and Texas Interconnections. Direct current lines connect the three divisions in a few locations, but these macro-grids most often work independently.
How Electricity is Delivered
The electricity grid in New England includes over 350 central power plants and 8,000 miles of high-voltage transmission lines to provide electricity to approximately 6.5 million customers. The capacity of this grid is 32,000 megawatts. Coordination by various entities at multiple levels is necessary to ensure the uninterrupted generation, transmission, and delivery of electricity. Here are some of the key organizations involved in making the grid work:
- ISO (Independent System Operator) New England
- Generators
- Suppliers
- Transmission companies
- Distribution companies
- Providers
- Municipally-owned utilities
The Independent System Operator of New England (ISO New England or ISO-NE) was established by the Federal Energy Regulatory Commission (FERC) to oversee the operation of the grid in the six New England states. Similar ISOs serve the same purpose in other regions of the U.S.
One of the major responsibilities of the ISO-NE is to provide stability to the power generation and transmission of electricity in New England. It also regulates the rates at which generators can sell power to transmission companies.
Generators
Generators are power plants that produce electricity. These power plants are independently owned, but the amount of electricity generated is overseen by the ISO-NE.
Suppliers
Suppliers purchase electricity from the generators and sell it to end users (consumers). Consumers can choose their supplier.
Transmission and Distribution Companies
Transmission and distribution companies own most of the wires that make up the electricity grid (though some municipalities own the generation, transmission, and distribution of their electricity through municipally-owned utilities). They are responsible for getting electricity from power plants to consumers. Collectively, the various transmission and distribution companies maintain the wires, high-voltage lines, transformers, and transmission substations that are used to transmit and distribute electricity. The distribution companies maintain the power lines within a given service territory and are also responsible for customer service, meter reading, and restoring power after outages.
In Massachusetts, four utilities are known as "investor-owned" or publicly-owned utilities. The following table shows the companies that serve Massachusetts and the relationship between their transmission and distribution entities.
| Transmission Company | Distribution Company | Areas Serviced |
| National Grid* | Massachusetts Electric Nantucket Electric |
portions of the northeast, southeast, central, and western MA; Nantucket |
| NSTAR | NSTAR | Boston area, Cape, and SE MA |
| The Northeast Utilities System* | Western Massachusetts Electric | Western MA |
| Unitil Corporation* | Fitchburg Gas & Light | Ashby, Townsend, Lunenburg, and Fitchburg in north-central MA |
| *also provide service outside of Massachusetts | ||
Approximately 45 communities in Massachusetts receive distribution services from separate municipal electric utilities. View a map of distribution company and municipal service territories in Massachusetts.
Municipally-Owned Utilities
Municipally-owned utilities are owned and operated by the individual towns and cities they serve. These utilities are responsible for customer billing, wire, pole, and meter maintenance, connecting new customers, distribution of electricity, and restoring power after an outage.
Across the U.S., over 2,200 utilities are municipally owned. The Massachusetts Municipal Wholesale Electric Company (MMWE) is a non-profit corporation that was formed to help municipal utilities offer electricity services at a rate competitive with investor-owned utilities.
Understanding Your Electricity Bill
If you live in an area served by investor-owned transmission and distribution companies, there are a several charges listed on your electric bill.
Delivery Services
Customer charge - metering, billing, and customer service provided by your distribution company
Distribution charge - the cost of the delivery of electricity to your home or business by the distribution company
Transition charge - the state's electricity law allows the distribution company to collect a fee that covers some of the expenses the company took on because of deregulation
Transmission charge - the cost of transmitting electricity from generators to the distribution company's service territory
Energy conservation - a small fee that is used for energy efficiency programs provided to customers
Renewable energy - a small fee that goes into a public fund at the Renewable Energy Trust to promote renewable energy. For most consumers, it is less than 50 cents per month.
Supplier Services
Generation charge -This charge is for the amount of electricity you actually use. The cost is determined by kilowatt hour, and depends on which supplier you choose. For customers who do not select a supplier, this charge is based on the distribution company's default rate per kilowatt hour.
Distributed Generation
An electricity generator can also be located at an individual site, providing power directly to the end users in that particular location. This is known as distributed generation because the generators are distributed at individual sites rather than being located at a central location serving many consumers.
Distributed generation systems (DG), also known as distributed energy resources, are located in close proximity to an individual consumer. DG systems are typically small-scale electricity generators, providing anywhere from a small share of a house's electricity to enough electricity for a factory, hospital, office building, or group of buildings. By comparison, a single central generator will generally produce enough electricity for hundreds, thousands, or even tens of thousands of buildings.
DG systems use a wide range of electricity generating technologies, ranging from renewable energy technologies like solar photovoltaics and small wind turbines, to fuel cells, natural gas microturbines, and diesel generators. In some cases, such as with diesel generators, the DG systems do not work all the time, but instead provide backup power when the electricity grid fails and is unable to provide electricity to the building.
In many DG systems, the consumer uses the distributed generation source to provide electricity whenever possible directly to a building and maintains a connection to the electricity grid in order to have access to centralized power when the DG system does not produce enough for the building's needs.
Benefits of Distributed Generation
Some of the benefits of DG systems are:
• The owner of the DG system reduces total electricity costs by avoiding paying the cost of distribution and transmission.
• If the owner of the DG system produces more electricity than is needed onsite, the surplus can often be sold to the utility company.
• Distributed generation systems may eventually reduce the cost of transmission and distribution upgrades for utilities since DG systems lower the demand for electricity from central generators.
• Distributed generation systems powered by renewable energy can significantly reduce air pollution, global warming, and other environmental impacts.
Distributed Generation Systems in Massachusetts
There are hundreds of DG systems in the state. Most are cogeneration plants (systems that generate electricity and also utilize the heat produced when the electricity is generated for another purpose such as heating the building), solar photovoltaic systems, and backup diesel generators. Small wind turbines and other renewable energy technologies can also be seen around the state.
The Renewable Energy Trust has provided funding for DG systems through several of its initiatives under the Green Buildings and Infrastructure Program. Click on this link to learn about the initiatives and specific DG installation projects.