Skip Navigation Links
About Natural Gas
Gas Utility Operations Best Practices Program
Energy Industry Analyses & Statistics
Find Industry Jobs
Find Vendors and Suppliers
Natural Gas Glossary
Operations & Engineering
Resources by Discipline
Residential Construction


A  | B  |  D  |  E  |  F  |  G  |  H  | I  | J  | K  | L  | M 

O  | R  | S  | U  |  V  |  W  |  Y  | Z


Earnings/Price Ratio (E/P)
A method to determine the cost of common equity component of return using the ratio of earnings per share to the stock price.
An acquired privilege or right, distinct from ownership of the soil, to use a specified area for certain specified uses.
Economic Out
Contract provisions enabling a company to get out of gas purchase contracts based on economic changes that are detrimental to the company.
Economic Potential
In DSM, an estimate of energy savings based on the assumption that all energy-efficient options will be adopted and all existing equipment will be replaced with the most efficient measure possible whenever it is cost-effective to do so, without regard to market acceptance. Compare ACHIEVABLE POTENTIAL, MARKET POTENTIAL and TECHNICAL POTENTIAL.
Economic Regulatory Administration (ERA)
Formerly the agency in the Department of Energy charged with the responsibility for imports of natural gas. In 1989, the ERA was eliminated and its functions were transferred to the Office of Fossil Energy (FE) in the Department of Energy.
Economic/Market Clauses
Contract provisions which allow price redetermination at specified times or conditions at prices prevailing in the area, or at market prices.
An arrangement of tubes through which the feed water passes before entering boiler drum and flue gases leave burners. Economizers are invariably counter flow; meaning the water flows opposite to the gases, and heat of gases is transferred to the water.
Edge Water
Subsurface water that surrounds gas and oil in reservoir structures.
Edwards Balance
An instrument for determining the specific gravity of gases. Compare BALANCE, GAS.
An energy efficient mortgage, often funded by Freddie Mac, Fannie Mae, VA or FHA, that recognizes the energy efficiency of a home and allows the lender to stretch the
Relating to heat, a percentage indicating the available Btu input to combustion equipment that is converted to useful purposes.
A material which at room temperature can be stretched repeatedly to at least twice its original length and upon immediate release of the stress, will return to its approximate original length and shape.
Electric Energy
Available heat in electricity; one kilowatt hour equals 3,412.97 Btu.
Electric Heating Pump and Air-Conditioning Efficie
Energy Efficiency Ratio (EER) - a ratio calculated by dividing the cooling capacity in Btu per hour by the power input in watts at any given set of rating conditions. Heating Seasonal Performance Factor (HSPF) - the total heating output of a heat pump during its normal annual usage period for heating divided by the total electric power input in watt-hours during the same period. Seasonal Energy Efficiency Ratio (SEER) - the total cooling capacity of a central unitary air conditioner or unitary heat pump in Btu's during its normal annual usage period for cooling divided by the total electric energy input in watt-hours during the same period.
Electric Log
Electric Space Heating
Space heating of a dwelling or business establishment or other structure using permanently installed electric heating as the principal source of space heating for a specific area or areas of the premises.
Electric Well Log
A record of electrical characteristics of formations drilled through. Electric logs are used to identify the formations, determine the nature and amount of fluids they contain, and estimate their depth. See LOG, ELECTRIC.
In a pipeline, the decomposition or destruction of the pipe wall by stray electrical currents. The chemical decomposition of a substance when electricity is passed through it in solution or in the molten state. When the process is applied to water or hydrogen, a potential energy source is formed.
Electronic Data Interchange (EDI)
The computer-to-computer exchange of business documents and information through the use of standard document formats.
Electronic Data Transfer
The computer-to-computer exchange of data for business transactions.
Electronic Gas Measurement (EGM)
"Real time" monitoring of natural gas quantities, and characteristics, as it passes through a specific location.
Electronic Ignition
A spark ignition device designed to electrically initiate the combustion process.
Elevated Temperature Testing
Tests on plastic pipe above 23oC (73oF).
Eligibility Criteria
Standards that describe the customers who can participate in a utility's DSM program.
Eligible Firm Sales Service Agreement
For purposes of establishing an open access pipeline's obligations to offer CD CONVERSION, an agreement between an open access interstate pipeline and a sales customer that was entered into before the date the pipeline became an open access transporter. See CD CONVERSIONS.
Eligible Market
The subset of the total market that is allowed to participate in a utility's DSM program based on eligibility criteria.
Ell or Elbow
A pipe fitting that makes an angle in a piperun. Unless stated otherwise, the angle is usually assumed to be 90 degrees. Compare STREET ELL.
The actual purpose for which gas is used by the ultimate consumer to whom it is delivered.
End-Use Metering
The direct measuring of consumption by specific end-use appliances, typically as part of load research studies or to measure the impacts of DSM programs.
An entity which is the ultimate consumer for natural gas. An end-user purchases the gas for consumption but not for resale purposes.
Heat absorbing. An endothermic reaction is one in which heat must be supplied to further the reaction.
Energy Audit
A review of a customer's energy usage, often including recommendations to alter the customer's demand or reduce energy usage. An audit normally involves a visit to the customer's facility.
Energy Conservation Measure
A device, material, or appliance used or installed to improve energy efficiency.
Energy Conservation Practice
Actions or practices taken to reduce energy consumption.
Energy Factor
A measure of the overall efficiency of a water heater, based on its recovery efficiency, standby loss and energy input as set out in standardized Department of Energy test procedures.
Energy Information Administration (EIA)
The statistical information collection and analysis branch of the Department of Energy.
Energy-Efficiency Program
A DSM program aimed at reducing overall consumption, often without regard for the timing of the program-induced savings. Such savings are generally achieved by substituting technically more efficient equipment to produce the same level of end-use services with less energy.
Engine, Reciprocating
An apparatus which converts the energy in a fluid to mechanical energy by means of the expansion of the fluid (gas) against a piston. It normally includes a cylinder closed by a piston connected by means of a connecting rod to a crankshaft; a valve mechanism admits and discharges fluid at appropriate times in the cycle. Compare TURBINE, STEAM OR GAS.
Enhanced Oil Recovery (EOR) Fields
Reservoirs in which secondary recovery techniques are used to extract oil. Most notably, EOR fields in Kern County, California, are expected to use large amounts of natural gas in the future to produce steam for secondary recovery, as well as electricity to be sold to local utilities.
Increasing the heat content of a gas by mixing with it a gas of higher Btu content.
Working interest owner's share of production. This volume may not equal actual sales due to contractual or market conditions. Also, the amount of gas to which a customer is entitled from a seller.
The aggregate of all surrounding conditions, influences, or forces affecting the life, development, and survival of an organism.
Environmental Protection Agency (EPA)
A federal agency created in 1970 to permit coordinated and effective governmental action, for protection of the environment by the systematic abatement and control of pollution, through integration of research monitoring, standard setting, and enforcement activities.
Environmental Stress Cracking (ESC)
Cracks that develop when the material is subjected to stress or strain in the presence of specific chemicals.
Epoxy Resins
Resins made by the reaction of epoxides or oxiranes with other materials such as amines, alcohols, phenols, carboxylic acids, acid anhydrides, and unsaturated compounds.
Equal Rate Treatment
Term used to designate a test of the reasonableness of an allocation of costs. In this test the rates designed to recoup the costs allocated to jurisdictional business are applied to the billing units of non-jurisdictional business to determine whether such rates will produce more or less revenues than the costs which have been assigned to the non-jurisdictional business. The "equal rate treatment" is also used as an allocation methodology. In this instance rates are designed which will recoup the total cost of service and are applied equally to jurisdictional and non-jurisdictional business.
Equitable Sharing Mechanism
One of two distinct mechanisms for passthrough of take-or-pay buyout costs of interstate natural gas pipelines. The first is pursuant to the Commission's historic policy of permitting prudently incurred costs to be recovered in the sales commodity rate. The second, alternate method was developed in Order No.500. The EQUITABLE SHARING MECHANISM, is available to open access pipelines which agree to an equitable sharing of take-or-pay costs and permits them to recover costs over a specified amortization period, such as five years. Where a pipeline agrees to absorb from 25 to 50 percent of take-or-pay costs, the Commission permits the pipeline to recover through a fixed charge an amount equal to, but not greater than, the amount absorbed. Any remaining costs up to 50 percent of total buyout and buydown costs may be recovered either through a commodity rate surcharge or a volumetric surcharge on total throughput. Fixed charges are allocated among firm sales customers in accordance with the PURCHASE DEFICIENCY METHODOLOGY. See BASE PERIOD and DEFICIENCY PERIOD.
Equity refers to the considerations of fairness or justice in the setting of rates - fairness between investors and consumers when the general level of rates is at issue, and the fairness among different classes of consumers when the rate relationships are under inquiry. Fair treatment in the setting of rates does not necessarily mean equal rates since, for example, the unit costs of serving different customer classes may be different. Also, that part of a business enterprise owned by the stockholders. Usually represented in the financial
Equity Capital
Investment capital provided by common and preferred stockholders.
Equity Return
The after-tax return to common and preferred stockholders.
Equivalent Direct Radiation
Heat expressed in terms of a square foot of steam radiator surface emitting 240 Btu per hour. (Btu per hour divided by 240).
Equivalent Length of Pipe
The resistance of pipe valves, controls, and fittings to gas flow expressed as equivalent length of pipe or pipe of other sizes, for convenience in calculating pipe diameters.
Equivalent of Fuels Burned
The Btu equivalent of fuels burned is the aggregate heat energy of all fuels burned. It is derived by calculating total Btu content of each kind of fuel burned and summing to establish the Btu content of all fuels burned. Based on its Btu content, any kind and quantity of fuel burned may be expressed as an equivalent quantity of some other kind of fuel.
Equivalent Quantities
A quantity of gas containing an amount of Btus equal to the amount of Btus received by Transporter for the account of Shipper at the Point(s) of Receipt reduced, where applicable, by the Btus removed for Transporter's compressor fuel and Transporter's lost-and-unaccounted for gas and BTU shrinkage in the treatment and processing of Shipper's gas, all as attributable to transportation of Shipper's gas.
Equivalent Volumes
The term "Equivalent Volumes" shall mean the sum of the volumes of gas measured in MMBtu received by Transporter for the account of Shipper at the Transporter Receipt Point(s) during any given period of time, (a) reduced by a percentage for Fuel Gas consumed and a percentage for Gas Lost and Unaccounted For on Transporter's system as provided in the Agreement, (b) reduced by any plant volume reductions assessed as a result of Shipper's or its supplier's election to process the gas, and (c) adjusted for any variations in Btu content. It is the intent of the parties that the volumes of gas delivered at the Transporter Delivery Point(s) after transportation shall be the equivalent in Balancing Units of the volumes of gas received at the Transporter Receipt Point(s) for transportation, as adjusted for items (a), (b) and (c) above.
Escalator Clause
A clause in a purchase or sales contract that permits adjustment of price or profit, under specific conditions.
Estimated Bill
Estimated Proved Recoverable Reserves
Ethane (C2H6)
A colorless hydrocarbon gas of slight odor having a gross heating value of 1,773 Btu per cubic foot and a specific gravity of 1.0488. It is a normal constituent of natural gas.
Ethylene (C2H4)
A colorless hydrocarbon gas of slight odor having a gross heating value of 1,604 Btu per cubic foot and a specific gravity of 0.9740. It is usually present in manufactured gas, constituting one of its elements.
An instrument for the volumetric measurement and analysis of gases.
Evaporative Cooling
The adiabatic exchange of heat between air and a water spray or wetted surface. The water approaches the wet bulb temperature of the air, which remains constant during its traverse of the exchanger.
Equipment or device that extracts or drives out vapors from liquid solutions or gases. Also, equipment that is part of refrigerating systems to permit liquid refrigerants to evaporate in the process of absorbing heat.
Evergreen Clause
A provision in a contract that provides for the automatic extension of the contract for specified periods beyond the primary term unless either party specifically elects to terminate the contract by giving the required notice prior to the anniversary date.
Ex Parte Communications
Off-the-record communication between any party to a proceeding before the Commission and any Commissioner, his or her staff, or any employee of the Commission.
Excess Air
Air which passes through a combustion zone in excess of the quantity theoretically required for complete combustion.
Exchange Agreement
An agreement between two parties which defines the terms and conditions for the exchange of gas and title transfer.
Exchange Gas
Gas that is received from (or delivered to) another party in exchange for gas delivered to (or received from) such other party.
Exchange Transactions
In a gas exchange between two parties, gas is received from (or delivered to) the first party in exchange for gas delivered to (or received from) the second party. An exchange provides a means for delivering gas supplies to a customer without the necessity of constructing and operating duplicative facilities. Central to the concept of an exchange is mutual benefits to the two parties engaging in the exchange. The transaction must involve reciprocal benefit or the trade of comparable values.
Exhaust Port
In engines, the opening through which a fluid discharges out of a cylinder. In gas meter, the openings through which gas leaves the metering chamber.
Exit Temperature
The flue gas temperature taken at the point where the gas leaves the combustion chamber.
That characteristic of a chemical reaction, such as fuel combustion, in which heat is liberated.
Expander Cycle
A liquefaction process using expansion turbines or engines to produce mechanical energy while refrigerating the gas to be liquefied.
Expander Turbine
A rotary motion machine employing the hot air blast of jet engines as the turning force.
Expansion Loop
Either a bend like the letter "U" or a coil in a line of pipe to provide for expansion and contraction.
Expansion Ratio
The ratio of gas volume after expansion to the gas volume before expansion.
Expansion Valve
A special valve used in refrigerating systems through which the liquid refrigerant (under high pressure) is allowed to escape into a lower pressure and thus expand into a gas.
Generally, the act of searching for potential subsurface reservoirs of gas or oil. Methods include the use of magnetometers, gravity meters, seismic exploration, surface mapping, exploratory drillings, and other such methods.
Exploratory Well
A well drilled either in search of a new and as yet undiscovered accumulation of oil or gas, or in an attempt to significantly extend the limits of a known reservoir.
Explosion Head
A term applied to a protective device that is arranged to blow out a disk, usually if an air-gas mixture explodes in a piping system. Thereafter, the gas will escape until a shut-off valve is closed.
Explosive Limits
The lowest (lower limit) and highest (upper limit) concentrations of a specific gas or vapor in mixture with air that can be ignited at ordinary temperature and pressure of the mixture. Also called COMBUSTIBLE LIMITS or FLAMMABLE LIMITS.
A substance, generally having some adhesive action, added to a plastic composition to reduce the amount of the primary resin required per unit volume.
Extension (of Gas Reserves)
Any new reserve credited to a previously producing reservoir because of enlargement of its producing area due to new well drilling or completions outside the previously known producing limits of the reservoir.
Exterior Zones
The portions of a building, with significant amounts of exterior walls, windows, roofs, or exposed floors. Such zones have heating or cooling needs largely dependent upon weather conditions. Compare INTERIOR ZONES.
Externality, Environmental
The environmental costs to society of the production, distribution and consumption of energy that are not reflected in the price to the end-users.
Extraction Loss
The reduction in volume of natural gas resulting from the removal of the natural gas liquid constituents of natural gas at extraction plants. See SHRINKAGE, NATURAL GAS.
Extraction Plant
A plant in which products, such as propane, butane, oil, ethane, or natural gasoline, which are initially components of the gas stream, are extracted or removed for sale. See GASOLINE PLANT.
Extraordinary Property Losses
An amortizable (Deferred Debit) account, which includes the depreciated value of property abandoned or damaged by circumstances that could not have been reasonably anticipated and which is not covered by insurance.
The process whereby heated or unheated plastic forced through a shaping orifice becomes one continuously formed piece.


Join the Energy Conversation