• Haulageay

    Main transportation tunnel for deep mines in which rail tracks have been laid for mine cars.

  • Head

    The vertical height of the water in a reservoir above the turbine. In general, the higher the head, the greater the capability to generate electricity.

  • Headstation

    Mainline receipt point on a pipeline.

  • Heat Content

    The sum of the latent heat and sensible heat contained in a substance, above the heat contained at a specified temperature and pressure; expressed as Btu or calories per unit of volume or weight. Also CALORIFIC VALUE.

  • Heat or Heating Rate

    The measure of efficiency in converting input fuel to electricity. Heat rate is expressed as the number of Btu's of fuel (e.g., natural gas) per kilowatt hour (Btu/kWh). Heat rate for power plants depends on the individual plant design, its operating conditions, and its level of electric power output. The lower the heat rate, the more efficient the plant.

  • Heating Value

    The amount of heat produced by the complete combustion of a unit quantity of fuel. The gross, or higher, heating value is that which is obtained when all of the products of combustion are cooled to the temperature existing before combustion, the water vapor formed during combustion is condensed, and all the necessary corrections have been made. The net, or lower, heating value is obtained by subtracting the latent heat of vaporization of the water vapor formed by the combustion of the hydrogen in the fuel from the gross, or higher, heating value.

  • Heavy Load Hours

    Generally speaking, this refers to the time of day on a system that would be considered peak demand. Actual hours vary by individual power system.

  • Heavy Oil

    The fuel oils remaining after the lighter oils have been distilled off during the refining process.

  • Hedging

    To offset a position with the intent of managing risk. The process of protecting the value of an investment from the risk of loss in case the price fluctuates. Hedging is accomplished by protecting one transaction with another. A long position in an underlying instrument can be hedged or protected with an offsetting short position in a related underlying instrument.

  • Helium, Contained

    The helium constituent in crude helium.

  • Helium, Crude

    The mixture of elemental helium and other constituents of natural gas, principally nitrogen, extracted from natural gas by helium extraction plants. Crude helium is typically 60-80% contained helium.

  • Helium (HE)

    A light, colorless, nonflammable gaseous element found especially in conjunction with natural gas and used mainly in cryogenic applications, medical technology, military uses, and welding.

  • Helium, Refined

    Helium that is of a high level of purity after the processing of crude helium.

  • Herfindahl-Hirschman Index (HHI)

    A formula for defining market concentration by summing the squares of the individual market shares of all participants.

  • High Transmission Voltage

    A measure of frequency of electric current in North America. The standard frequency is 59.5 - 60.5 hertz.

  • Highwall

    The unexcavated face of exposed overburden and coal of a surface mine or the exposed face or bank of a hill on the uphill side of a contour mine excavation site.

  • Hinshaw Pipeline

    A pipeline company (defined by the Natural Gas Act and exempted from FERC jurisdiction under the NGA) defined as a regulated company engaged in transportation in interstate commerce, or the sale in interstate commerce for resale, of natural gas received by that company from another person within or at the boundary of a state, if all the natural gas so received is ultimately consumed within such state. A Hinshaw pipeline may receive a certificate authorizing it to transport natural gas out of the state in which it is located, without giving up its status as a Hinshaw pipeline.

  • Historic Sales Customers

    A pipeline's traditional customers who purchased bundled sales service from the pipeline prior to Order No. 636.

  • Hopper Cars

    Open freight cars with a floor sloping to one or more hinged doors for discharging bulk materials such as coal.

  • Host Control Area

    The control area within the metered boundaries a unit not owned by the host or a unit jointly owned by the host and another entity is physically located.

  • Hourly Peak

    The maximum demand for energy from a transmission or distribution system in any hourly period of time.

  • Hourly Value

    Data measured on a clock-hour basis.

  • Hub

    An interchange where multiple pipelines or electric transmission lines interconnect and form a market center.

  • Hydrocarbon

    Organic compound made up of carbon and hydrogen atoms. Heavier fossil fuels, such as coal, have a large ratio of carbon to hydrogen, while natural gas (methane) is the lightest hydrocarbon, with one atom of carbon and four atoms of hydrogen (CH4). Natural gas liquids are heavier than methane but lighter than crude oil. Crude oil is a complex of many hydrocarbons.

  • Hydroelectric Plant

    A plant in which the turbine generators are driven by falling water.