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R–Value: A unit of thermal resistance used for comparing insulating values of different material. It is basically a measure of the effectiveness of insulation in stopping heat flow. The higher the R–value number, a material, the greater its insulating properties and the slower the heat flow through it. The specific value needed to insulate a home depends on climate, type of heating system and other factors.

Rack (Terminal) Price: Wholesale price.

Rack Sales: Wholesale truckload sales or smaller of gasoline where title transfers at a terminal.

RAD: A unit of measure of absorbed radiation. Abbreviation for Radiation Absorbed Dose. One rad equals 100 ergs of radiation energy per gram of absorbing material.

Radiant Barrier: A device designed to reduce or stop the flow of radiant energy.

Radiant Energy: Energy transferred by the exchange of electromagnetic waves from a hot or warm object to one that is cold or cooler. Direct contact with the object is not necessary for the heat transfer to occur.

Radiation: The flow of energy across open space via electromagnetic waves such as light. Passage of heat from one object to another without warming the air space in between.

Rankine Cycle: The steam–Rankine cycle employing steam turbines has been the mainstay of utility thermal electric power generation for many years. The cycle, as developed over the years, uses superheat, reheat and regeneration. Modern steam Rankine systems operate at a cycle top temperature of about 1,073 degrees Celsius with efficiencies of about 40 percent.

Raw Fuel: Coal, natural gas, wood or other fuel that is used in the form in which it is found in nature, without chemical processing.

Reactor: A device in which a controlled nuclear chain reaction can be maintained, producing heat energy.

Reclaimed Oil: Lubricating oil that is processed to be used over again.

Recovered Energy: Reused heat or energy that otherwise would be lost. For example, a combined cycle power plant recaptures some of its own waste heat and reuses it to make extra electric power.

Refined Petroleum Products: Refined petroleum products include but are not limited to gasolines, kerosene, distillates (including No. 2 fuel oil), liquefied petroleum gas, asphalt, lubricating oils, diesel fuels, and residual fuels.

Refiner: Any person who owns, operates, or controls the operations of one or more refineries.

Refinery: A facility that separates crude oil into varied oil products. The refinery uses progressive temperature changes to separate by vaporizing the chemical components of crude oil that have different boiling points. These are distilled into usable products such as gasoline, fuel oil, lubricants, and kerosene.

Refinery Margin: The difference between the spot price of refined petroleum products and the price of crude oil.

Reforestation: Replanting of forests on lands that have recently been harvested.

Reformulated Gasoline: Finished gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regulations promulgated by the U.S. Environmental Protection Agency under Section 211(k) of the Clean Air Act. In other words, a cleaner–burning gasoline that has had its compositions and/or characteristics altered to reduce vehicular emissions of pollutants. Reformulated gasoline includes gasoline produced to meet or exceed emissions performance and benzene content standards of federal–program reformulated gasoline even though the gasoline may not meet all of the composition requirements (e.g. oxygen content) of federal–program reformulated gasoline. Note: This category includes Oxygenated Fuels Program Reformulated Gasoline (OPRG). Reformulated gasoline excludes Reformulated Blendstock for Oxygenate Blending (RBOB) and Gasoline Treated as Blendstock (GTAB).

Refrigerant: A fluid such as freon that is used in cooling devices to absorb heat from surrounding air or liquids as it evaporates.

Refuse Derived Fuel (RDF): The fuel component of municipal solid waste (MSW), which is the by–product of shredding MSW to a uniform size, screening out oversized materials and isolating ferrous material in magnetic separation. The resulting RDF can be burned as a fuel source.

Regional Transmission Group (RTG): A voluntary organization of transmission owners, users and other entities interested in coordinating transmission planning, expansion, operation,and use on a regional and inter–regional basis. Such groups are subject to Federal Energy Regulatory Commission approval.

Regular Grade Gasoline: Gasoline having an antiknock index, i.e., octane rating, greater than or equal to 85 and less than 88. Note: Octane requirements may vary by altitude.

Regular Unleaded Gasoline: Gasoline having an antiknock index, i.e., octane rating, greater than or equal to 85 and less than 88 and containing no more than 0.05 gram of lead per gallon and no more than 0.005 gram of phosphorus per gallon. Notes: Octane requirements may vary by altitude. Premium regular and midgrades are included, depending on the octane rating.

Reid Vapor Pressure (RVP): A standard measurement of a liquid's vapor pressure in pounds per square inch at 100 degrees Fahrenheit. It is an indication of the propensity of the liquid to evaporate.

Reliability: Electric system reliability has two components––adequacy and security. Adequacy is the ability of the electric system to supply the aggregate electrical demand and energy requirements of the customers at all times, taking into account scheduled and unscheduled outages of system facilities. Security is the ability of the electric system to withstand sudden disturbances such as electric short circuits or unanticipated loss of system facilities.

Renewable Energy: Resources that constantly renew themselves or that are regarded as practically inexhaustible. These include solar, wind, geothermal, biomass including alcohol fuels, hydro and wood. Although particular geothermal formations can be depleted, the natural heat in the earth is a virtually inexhaustible reserve of potential energy. Renewable resources also include some experimental or less–developed sources such as tidal power, sea currents and ocean thermal gradients.

Renewable Energy Resources: Renewable energy resources are naturally replenishable, but flow–limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Some (such as geothermal and biomass) may be stock–limited in that stocks are depleted by use, but on a time scale of decades, or perhaps centuries, they can probably be replenished. Renewable energy resources include: biomass, hydro, geothermal, solar, wind, and wood. In the future they could also include the use of ocean thermal, wave, and tidal action technologies. Utility renewable resource applications include bulk electricity generation, on–site electricity generation, distributed electricity generation, non–grid–connected generation, and demand–reduction (energy efficiency) technologies.

Reregulation: The design and implementation of regulatory practices to be applied to the remaining regulated entities after restructuring of the vertically–integrated electric utility. The remaining regulated entities would be those that continue to exhibit characteristics of a natural monopoly, where imperfections in the market prevent the realization of more competitive results, and where, in light of other policy considerations, competitive results are unsatisfactory in one or more respects. Reregulation could employ the same or different regulatory practices as those used before restructuring.

Research And Development (R&D): Research is the discovery of fundamental new knowledge. Development is the application of new knowledge to develop a potential new service or product. Basic power sector R&D is most commonly funded and conducted through the Department of Energy, its associated government laboratories, university laboratories, the Electric Power Research Institute (EPRI) and private sector companies.

Reserve: The extra generating capability that an electric utility needs, above and beyond the highest demand level it is required to supply to meet its users’ needs.

Reserve Generating Capacity: The amount of power that can be produced at a given point in time by generating units that are kept available in case of special need. This capacity may be used when unusually high power demand occurs, or when other generating units are off–line for maintenance, repair or refueling.

Reserve Margin: The differences between the dependable capacity of a utility's system and the anticipated peak load for a specified period.

Residential Building: Means any hotel, motel, apartment house, lodging house, single and dwelling, or other residential building which is heated or mechanically cooled.

Residential Sector: Private households that consume energy primarily for heating, water heating, air conditioning, lighting, refrigeration, and cooking.

Residual Fuel: The heavier oils that remain after the distillate fuel oils and lighter hydrocarbons are distilled away in refinery operations.

Residue: Any organic matter left as residue, such as agricultural and forestry residue, including, but not limited to, conifer thinnings, dead and dying trees, commercial hardwood, noncommercial hardwoods and softwoods, chaparral, burn, mill, agricultural field, and industrial residues and manure.

Resistance (Electrical): The ability of all conductors of electricity to resist the flow of current, turning some of it into heat. Resistance depends on the cross section of the conductor (the smaller the cross section, the greater the resistance) and its temperature (the hotter the cross section, the greater its resistance).

Resistance (Thermal): The reciprocal of thermal conductance. See R–Value.

Resource Efficiency: The use of smaller amounts of physical resources to produce the same product or service. Resource efficiency involves a concern for the use of all physical resources and materials used in the production and use cycle, not just the energy input.

Restructuring: The reconfiguration of a vertically–integrated utility. Restructuring usually refers to separation of the various utility functions into individually–operated and –owned entities.

Retail Competition: A system under which more than one electric or natural gas provider can sell to retail customers, and retail customers are allowed to buy from more than one provider. See Direct Access.

Retail Market: A market in which electricity and other energy services are sold directly to the end–use customer.

Retail Sales: Sales of electric energy to residential, commercial, and industrial end–use customers.

Retail Wheeling: See Direct Access.

Retorting: The heating of oil shale to get the oil out from it.

Retrofit: A broad term that applies to any change after the original purchase, such as adding equipment not a part of the original purchase. As applied to alternative fuel vehicles, it refers to conversion devices or kits for conventional fuel vehicles. Also called "aftermarket."

Road Oil: Any heavy petroleum oil, such as residual alphaltic oil, used as a dust palliative and surface treatment on roads and highways.

Rural Electric Cooperative: A nonprofit, customer–owned electric utility that distributes power in a rural area.