Natural Gas Glossary

British Thermal Unit (Btu) - The quantity of heat necessary to raise the temperature of one pound of water one degree Fahrenheit from 58.5 to 59.5 degrees Fahrenheit under standard pressure of 30 inches of mercury at or near its point of maximum density. One Btu equals 252 calories, (gram), 778 foot-pounds, 1,055 joules or 0.293 watt hours.

By-Products (Residuals) - Secondary products which are obtained from the processing of a raw material and have commercial value. They may be the residues of the gas production process, such as coke, tar and ammonia, or they may be the result of further processing of such residues, such as ammonium sulphate.

Carbon Monoxide (CO) - A colorless, odorless combustible gas formed by incomplete combustion of carbon, or reduction of carbon dioxide.

City Gate Station - Point at which a distribution gas company receives gas from a pipeline company.

Coke - A porous, solid residue resulting from the incomplete combustion of coal heated in a closed chamber, or oven, with a limited supply of air. Coke is largely carbon and is a desirable fuel in certain metallurgical industries.

Commodity Charge - A charge per unit volume or heat content (i.e., therm) of gas delivered to the buyer.

Consumption - The quantity of natural gas used by ultimate consumers.

Cubic Foot  - The most common unit of measurement of gas volume. It is the amount of gas required to fill a volume of one cubic foot under stated conditions of temperature, pressure and water vapor.

Daily Average Sendout - The total quantity of gas delivered for a period of time divided by the number of days in the period.

Degree Day, Heating - A measure of the coldness of the weather experienced, based on the extent to which the daily mean temperature falls below a reference temperature, usually 65 degrees Fahrenheit. For example, on a day when the mean outdoor dry-bulb temperature is 35 degrees Fahrenheit, there would be 30 degrees days experienced. A daily mean temperature usually represents the sum of the high and low readings divided by two.

Fixed Cost - Certain costs which in the aggregate do not vary in amount regardless of the quantity of gas sold or transported.

Liquefied Natural Gas (LNG) - Natural gas which has been liquefied by reducing its temperature to minus 260 degrees Fahrenheit at atmospheric pressure. It remains a liquid at minus 116 degrees Fahrenheit and 673 psig. In volume, it occupies 1/600 of that of the vapor at standard conditions.

Manufactured Gas - A gas obtained by destructive distillation of coal, by the thermal decomposition of oil, or by the reaction of steam passing through a bed of heated coal or coke. Examples are coal gasses, coke or oven gases, producer gas, blast furnace gas, blue (water) gas, or carbureted water gas. The Btu content varies widely.

Rate Case - A proceeding before a regulatory commission involving the rates to be charged for a public utility service.

Spot Market - A market characterized by short-term, interruptible (or best efforts) contracts for specified volumes of gas. Participants may be any of the elements of the gas industry; producer, transporter, distributor or end user. Brokers may also be utilized.

Storage, Underground - The utilization of subsurface facilities for storing gas which has been transferred from its original location for the primary purposes of load balancing. The facilities are usually natural geological reservoirs such as depleted oil or gas fields or water-bearing sands sealed on the top by an impermeable cap rock. The facilities may be man-made or natural caverns.

Therm - A unit of heating value equivalent to 100,000 British thermal units (Btu).