(A - E) (F - J) (K - O) (P - T) (U - Z)

  • Daily Peak : The maximum amount of energy or service demanded in one day from a company or utility service.
  • Degree-day : A unit measuring the extent to which the outdoor mean (average of maximum and minimum) daily dry-bulb temperature falls below (in the case of heating) or rises above (in the case of cooling) an assumed base. The base is normally taken as 65 degrees for heating and cooling unless otherwise designated.
  • Demand (electric) : The rate at which electric energy is delivered to or by a system, part of a system, or a piece of equipment. Demand is expressed in kW, kVA, or other suitable units at a given instant or over any designated period of time. The primary source of "demand" is the power-consuming equipment of the customers.
  • Demand Billing : The electric capacity requirement for which a large user pays. It may be based on the customer's peak demand during the contract year, on a previous maximum or on an agreed minimum. It is measured in kilowatts.
  • Demand Charge : The sum to be paid by a large electricity consumer for its peak usage level.
  • Demand Controller : An electrical, mechanical, or electromechanical device or system that monitors the customer demand and causes that demand to be leveled and/or limited.
  • Demand Ratchet : This is the minimum billing demand based upon a given percentage of the actual demand use, recorded during the last eleven months of demand history.
  • Demand-Side Management (DSM) : A technology or program that encourages customers to use electricity differently.
  • Demonstration : The application and integration of a new product or service into an existing or new system. Most commonly, demonstration involves the construction and operation of a new electric technology interconnected with the electric utility system to demonstrate how it interacts with the system. This includes the impacts the technology may have on the system and the impacts that the larger utility system may have on the functioning of the technology.
  • Departing Member : A member consumer served at retail by an electric cooperative corporation that hs given notice of intent to receive generation services from another source or that is otherwise in the process of changing generation suppliers. These persons shall nonetheless remain members of the electric distribution cooperative corporation for purposes of distribution service.
  • Dependable Capacity : The system's ability to carry the electric power for the time interval and period specified. Dependable capacity is determined by such factors as capability, operating power factor and portion of the load the station is to supply.
  • Depletable Energy Sources : This includes: 1) electricity purchased from a public utility and 2) energy obtained from burning coal, oil, natural gas or liquefied petroleum gasses.
  • Depreciation, Straight-line : Straight-line depreciation takes the cost of the asset less the estimated salvage value and allocates the cost in equal amounts over the asset's estimated useful life.
  • Deregulation : The elimination of regulation from a previously regulated industry or sector of an industry.
  • Designated Agent : An agent that acts on behalf of a transmission provider, customer or transmission customer as required under the tariff.
  • Direct Access : The ability of a retail customer to purchase commodity electricity directly from the wholesale market rather than through a local distribution utility.
  • Direct Current (DC) : Electric that flows continuously in the same direction.
  • Direct Energy Conversion : Production of electricity from an energy source without transferring the energy to a working fluid or steam. For example, photovoltaic cells transform light directly into electricity. Direct conversion systems have no moving parts and usually produce direct current.
  • Direct Load Control : Activities that can interrupt load at the time of peak by interrupting power supply on consumer premises, usually applied to residential consumers.
  • Direct Utility Cost : A cost identified with one of the DSM categories.
  • Disaggregation : The functional separation of the vertically integrated utility into smaller, individually owned business units (I.e. generation, dispatch/control, transmission, distribution). The terms "deintegration", "disintegration" and "delimitation" are sometimes used to mean the same thing.
  • Discount/Interest Rate : The discount rate is used to determine the present value of future or past cash flows. The rate accounts for inflation and the potential earning power of money.
  • Dispatchability : This is the ability of a generating unit to increase or decrease generation, or to be brought on line or shut down at the request or a utility's system operator.
  • Distributed Generation : A distributed generation system involves small amounts of generation located on a utility's distribution system for the purpose of meeting local (substation level) peak loads and/or displacing the need to build additional (or upgrade) local distribution lines.
  • Distribution : The system of wires, switches, and transformers that serve neighborhoods and business, typically lower than 69,000 volts. A distribution system reduces or downgrades power from high-voltage transmission lines to a level that can be used in homes or businesses.
  • Distribution Line : This is a line or system for distributing power from a transmission system to a customer. It is any line operating at less than 69,000 volts.
  • Distribution System : That part of the electric system that delivers electric energy to consumers.
  • Distribution Utility (Disco) : The regulated electric utility entity that constructs and maintains the distribution wires connecting the transmission grid to the final customer. The Disco can also perform other services such as aggregating customers, purchasing power supply and transmission services for customers, billing customers and reimbursing suppliers, and offering other regulated or non-regulated energy services to retail customers. The "wires" and "customer service" functions provided by a distribution utility could be split so that two totally separate entities are used to supply these two types of distribution services.
  • Distributive Power : A packaged power unit located at the point of demand. While the technology is still evolving, examples include fuel cells and photovoltaic applications.
  • Diversity Exchange : Exchange of capacity or energy between systems that have peak loads occurring at different times.
  • Diversity Factor : The ratio of the sum of the non-coincident maximum demands of two or more loads to their coincident maximum demand for the same period.
  • Divestiture : The stripping off of one utility function from the others by selling (spinning-off) or in most other way changing the ownership of the assets related to that function. Most commonly associated with spinning-off generation assets so they are no longer owned by the shareholders that own the transmission and distribution assets.
  • DSM Measure Technology Program : Single devices, equipment, or rates as listed in the Reference Data. A demand-side management program is usually a group of DSM measures or technologies. However, a DSM program could in some cases be a single measure.

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