Greenhouse Gases

A family of gases that trap radiant energy in the atmosphere. Commonly reported (and in some cases regulated) greenhouse gases include carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride. Human beings are increasing the amount of greenhouse gases in the atmosphere by burning fossil fuels. These increases affect our environment through climate change and its associated impacts (e.g., more extreme weather, species migration).

Carbon Offset

One metric ton (about 2,200 pounds) of greenhouse gas emissions reduced (or avoided) from projects such as methane capture at landfills, reforestation and energy efficiency. Carbon offsets can help balance out an individual’s or entity’s carbon footprint, allowing them to have a smaller net impact on climate change. High quality carbon offsets should be real, permanent, verifiable and beyond "business as usual."

Carbon Footprint

A measure of the carbon dioxide and other greenhouse gas emissions produced by or in support of an individual’s or entity’s activities over a defined period of time, typically a year.  Activities that contribute to an individual’s or entity’s carbon footprint typically include electricity and heating fuel usage, vehicle and air travel, and waste disposal. At the organizational level, some entities choose to measure the upstream emissions associated with the products and services that they purchase.

Carbon Dioxide (CO2)

CO2 is naturally present in the Earth's atmosphere and is a greenhouse gas considered to be the main human-made contributor to global warming and climate change. Burning fossil fuels to produce electricity and drive our cars releases significant amounts of CO2 into the atmosphere.


Fuel derived from plant and organic matter that is used to generate electricity. Landfill gas is one of the most widely used forms of biomass generation. At those facilities, gases from decomposing organic matter are collected and burned to generate electricity. While biomass-based generation is not entirely pollution-free, it does not contribute to global warming and produces much less pollution than more traditional sources of electricity such as coal.

Climate Change

The ongoing transformation of the Earth's average climate over time (from decades to millions of years). The majority of the world's climate scientists have concluded that greenhouse gas emissions resulting from human activities, such as transportation and electricity production, have a significant impact on the atmosphere and are having a discernible influence on global climate, which in turn affects people and the environment.

Distribution System

The local poles, wires, transformers, substations and other equipment used to deliver electricity to end-use consumers from high-voltage transmission lines. See "Grid."

Energy Efficiency

A measure of how efficiently a person, entity, or equipment uses energy. Some utilities and other entities offer energy efficiency programs aimed at reducing overall electricity consumption through the use of more energy-efficient equipment or behavior change, often without explicit consideration for the timing of program-induced savings (programs that consider timing may be referred to as load control, load management, or demand response).

Greenhouse Effect

The increasing average global surface temperature of the Earth caused by gases in the atmosphere (including carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbon). The greenhouse effect allows solar radiation to penetrate but reflects the infrared radiation returning to space back towards the Earth’s surface, causing overall warming over time.

Green Tag

See Renewable Energy Certificate (REC).

Green Electricity

A subset of renewable energy that provides the highest environmental benefit. The U.S. Environmental Protection Agency defines green power as “electricity produced from solar, wind, geothermal, biogas, biomass, and low-impact small hydroelectric sources.” See also Renewable Energy.


Green-e® is a third-party certification program administered by the Center for Resource Solutions. Green-e Energy® is the leading voluntary certification program for renewable energy in the U.S.


Energy generated by heat stored beneath the Earth's surface.

Generation Charges

The part of every customer's electricity bill that goes toward producing electricity. In deregulated electric markets, generation is competitively priced and is not regulated by the state. Generation charges are determined by suppliers, like Green Mountain Energy Company, or may be negotiated by entities such as aggregators and utility partners.

Fossil Fuels

Fossil fuels are formed from the decayed remains of prehistoric plants and animals. Examples include coal, natural gas, oil, petroleum, coke, and other petroleum-based fuels. Fossil fuels are in finite supply and are a non-renewable energy source. All fossil fuels contain carbon and, when used to make electricity, create carbon dioxide, a major greenhouse gas.


An existing or planned location or site at which electric generating units are situated or will be situated. A facility may contain more than one generating unit. For example, a wind farm—representing the facility—typically has multiple turbines—representing the generating units.

Energy Source

The primary fuel source that provides the energy that is converted to electricity through chemical, mechanical, or other means. Energy sources include fossil fuels, like coal, natural gas, petroleum and petroleum products as well as renewable sources like water, wind, sunlight, geothermal and biomass.


A network for the transmission of electricity throughout a region. The term is also used to refer to the layout of an electric distribution system.


The rate at which energy is converted from one form into another, or more simply, the rate at which it is generated or used. When talking about electricity, power is measured in kilowatts (kW) or megawatts (MW, or 1,000 kW). A wind turbine rated at 3 MW can convert wind energy into electrical energy more quickly than a wind turbine rated at 1.5 MW.


Blocks of time when energy demand is relatively lower (off-peak) or higher (on-peak).

Nitrogen Oxides (NOx)

Formed when fossil fuels (notably oil, coal and natural gas) and biomass (plant matter, wood chips and landfill gas) are burned at high temperatures. NOx contributes to acid rain and smog. Health effects associated with smog include damage to lung tissue, increased asthma attacks and respiratory illness in children with frequent high-level exposure. When NOx causes acid rain, it contributes to pollution of lakes and coastal waters and the degradation of sensitive forests. This pollution is destructive to fish and other animal life. Electricity generation is a primary source of NOx pollution.

New Renewables

A renewable energy facility or source qualifies as “new” if it was built (or repowered) within 15 years from the year in which the electricity or renewable energy certificate generated by the facility is produced (e.g., 1999 for 2013, 2000 for 2014). The new date is a requirement of the Center for Resource Solutions, which administers the Green-e Energy® Program.

Meter Read

Recording the amount of electrical energy used by homes and businesses as displayed by an electricity meter. Electricity meters are typically mounted on the exterior walls of homes and businesses. Most record total kilowatt hours of energy used per month and are usually read monthly by utility employees.

Megawatt-hour (MWh)

A unit of energy. One MWh equals 1 million watt-hours, which is the same as running a 100-watt light bulb for 10,000 hours or ten thousand 100-watt light bulbs for one hour.

Megawatt (MW)

A unit of power. A megawatt equals one thousand kilowatts (kW), or a million watts. When talking about an individual residential customer, the kW is typically used. When talking about a group of customers, a large commercial customer, or the power output of power plants, MW is often used. A large utility power plant typically has a power rating of 500 to 1,000 MW.

Kilowatt Hour (kWh)

A unit of energy. One kWh equals 1,000 watt-hours, which is the same as running a 100-watt light bulb for 10 hours or ten 100-watt light bulbs for one hour.

Kilowatt (kW)

A unit of power. One kW equals 1,000 watts. Ten 100-watt light bulbs, for example, have a total power rating of one kilowatt.


The force or energy of moving water used to generate electricity.

Renewable Energy

Energy sources that are either inexhaustible (solar, wind) or replenished over a short period of time (hydro, biomass, geothermal). Most renewable energy ultimately comes from the sun - indirectly in the case of wind, water, and biomass; directly in the case of solar generation. Natural gas and coal, for example, are not renewable resources because their use consumes gas and coal reserves at a much quicker rate than they can be replenished.

Renewable Energy Certificates (RECs)

Renewable energy certificates (referred to as RECs, and also known as renewable energy credits) represent the environmental and other non-power attributes of renewable electricity generation and are part of most renewable electricity products.

One RECs equals 1 megawatt-hour (MWh) of energy generated from renewable sources like wind, solar, hydro and biomass. They can be traded separately from the actual electricity produced by renewable facilities. Purchasing RECs ensures that the renewable electricity products you buy are generated using renewable resources, reducing the amount of electricity that has to be generated from polluting fossil fuels.

View RECs for individuals | View RECs for businesses

Wind Power

The conversion of wind energy into more useful forms, usually electricity, using wind turbines. Learn more.

Transmission Lines

Interconnected electric lines which move high voltage electricity from a generation facility ultimately to the distribution lines of an electric distribution company. See Grid.

Transmission Charges

Part of the basic service charges on every customer's bill for transporting electricity from the source of supply to the electric distribution company. The Federal Energy Regulatory Commission regulates retail transmission prices and services.

Tradable Renewable Certificates (TRCs)

See Renewable Energy Certificate (REC).

System Power

Grid-delivered electricity that represents the average mix of electricity produced from all power plants, regardless of their fuel (e.g., coal, natural gas, nuclear, wind). In the U.S., coal, natural gas and nuclear generation are the most-used sources for system power.

Sulfur Dioxide (SO2)

Formed by burning sulfur-containing fuels, primarily coal and oil. Major health effects associated with SO2 include asthma, respiratory illness and aggravation of existing cardiovascular disease. SO2 combines with water and oxygen in the atmosphere to form acid rain, which raises the acid levels of lakes and streams and can harm fish and some amphibians. It also damages sensitive forests and ecosystems and accelerates the decay of buildings. Electricity generation is a primary source of SO2 pollution.

Solar Energy

Energy from the sun. Sunlight can be converted to electricity directly, as in the case of photovoltaic applications or indirectly as in the case of solar thermal (hot water) applications. According to the U.S. National Renewable Energy Laboratories, the amount of energy from the sun that falls to the earth in one day could supply the entire world's energy needs for 27 years. Learn more.

New York

Public Service Commission (PSC)

The state governing body that provides oversight, policy guidance and direction to electric public utilities.


An energy service company (ESCO) is a non-utility company that provides electric and/ or gas service to residential and commercial customers in New York. ESCOs are licensed and regulated by the DPS. Green Mountain Energy Company is an ESCO.

Electric Supply Charges

The part of every customer's electricity bill that goes toward producing electricity. In deregulated electric markets, generation is competitively priced and is not regulated by the state. Electric supply charges are determined by energy service companies (ESCOs), like Green Mountain Energy Company.

Department of Public Service (DPS)

The New York State Department of Public Service (DPS) is the government agency that regulates public utilities. DPS is the staff arm to the Public Service Commission.


PUC Assessment

A fee assessed to recover the statutory fee for administering the Public Utility Regulatory Act.

Public Utility Commission of Texas (PUCT)

The state regulatory agency that provides oversight, policy guidance and direction to electric public utilities. Learn more.

Nuclear Decommisioning Fee

A charge assessed to recover a TDU’s charges for decommissioning of nuclear generating sites.

Meter Charge

A charge assessed to recover a TDU’s charges for metering a customer’s consumption, to the extent that the TDU charge is a separate charge exclusively for that purpose that is approved by the Public Utility Commission.

Late Payment Penalty

A charge assessed for late payment in accordance with Public Utility Commission rules.

Gross Receipts Reimbursement

or "Miscellaneous Gross Receipts Tax Reimbursement"; a fee assessed to recover the miscellaneous gross receipts tax imposed on retail electric providers operating in an incorporated city or town having a population of more than 1,000.


The Electric Reliability Council of Texas (ERCOT). Responsible for system reliability and competitive wholesale market in Texas. ERCOT is also responsible for centralized power scheduling, transactions and evaluation of balanced schedules to ensure reliability.

Energy Efficiency Cost Recovery Factor

A charge assessed to recover a TDU’s costs for energy efficiency programs to the extent that the TDU charge is a separate charge exclusively for that purpose that is approved by the Public Utility Commission.

Energy Charge

A charge based on the electric energy (kWh) consumed.

Retail Electric Provider (REP)

A company licensed to provide electric generation products and services to end-use customers. Green Mountain Energy Company is a REP licensed by the Public Utility Commission of Texas.

Sales Tax

Sales tax collected by authorized taxing authorities, such as the state, cities and special purpose districts.

System Benefit Fund

A non-bypassable charge approved by the Public Utility Commission, not to exceed 65 cents per megawatt-hour, that funds the low-income discount, one-time bill payment assistance, customer education, commission administrative expenses and low-income energy efficiency programs.

Transmission Distribution Surcharges

One or more TDU surcharge(s) on a customer’s bill in any combination. Surcharges include charges billed as tariff riders by the TDU.

Transition Charge

A charge assessed to recover a TDU’s charges for securitized costs associated with the transition to competition.

TDU Delivery Charges

The total amounts assessed by a TDU for the delivery of electricity to a customer over poles and wires and other TDU facilities not including discretionary charges.


Transmission and distribution utility (TDU) or transmission and distribution service provider (TDSP).

Distribution Charges

Part of the basic service charges on every customer's bill for delivering electricity from the electric distribution company to your home or business. Distribution charges are regulated by the Public Utility Commission.

Demand Charge

A charge based on the rate at which electric energy is delivered to or by a system at a given instant, or averaged over a designated period, during the billing cycle.

Competition Transition Charge

A charge assessed to recover a TDU’s charges for nonsecuritized costs associated with the transition to competition.

Base Charge

A charge assessed during each billing cycle without regard to the customer’s demand or energy consumption.

Advanced Metering Charge

A charge assessed to recover a TDU’s charges for Advanced Metering Systems, to the extent that they are not recovered in a TDU’s standard metering charge.