Glossary by "M"

  • 360

    Magnetic field

    A description of the magnetic effect that electric currents and magnetic materials have on their surroundings. The magnetic field is a vector field meaning that it is characterized by both the direction and a magnitude of the magnetic influence.  

    Source: ESA Technical Working Group
  • 361

    Marginal cost

    See: Incremental cost
    Source: ESA Technical Working Group
  • 362

    Market clearing price

    In any exchange, sellers prefer to part with their assets for the highest price possible while investors interested in buying the same asset desire the lowest purchase price possible. At some point, a mutually agreeable price is reached between buyers and sellers. It is at this point that economists say the market has “cleared” and transactions take place. Thus, the clearing price of an asset is the price at which it was most recently traded.

  • 363


    A unit of power equal to one million watts.

  • 364


    Acronym(s): MWh

    A measure involving one million watts being generated, transmitted, distributed or used continuously for one hour. The MegaWatt-hour a common unit of electric energy. (Note the difference between MegaWatt-hours of energy and a Megawatt of power where power reflects the rate at which electric energy is generated, transmitted, distributed or used).

    Source: ESA Technical Working Group
  • 365

    Merit order rank

    Ranking of electric supply resources according to their availability and the price that will be applied to the energy they produce.  

    Source: ESA Technical Working Group
  • 366


    A combination of co-located distributed electric resources that can operate as one entity that either 1. interacts with the greater electric grid (if available) or 2. as an autonomous power system that is not connected with a large power system (i.e. in “island” mode).

    Source: ESA Technical Working Group
  • 367

    Midwest Independent Transmission System Operator, Inc.

    Acronym(s): MISO

    An Independent System Operator (ISO) and Regional Transmission Organization (RTO) providing open-access transmission service and that monitors the high voltage transmission system throughout the Midwest United States and Manitoba, Canada.

  • 368

    Midwest Reliability Organization

    Acronym(s): MRO

    Midwest Reliability Organization (MRO) is a non-profit organization dedicated to ensuring the reliability and security of the bulk power system in the north central region of North America, including parts of both the United States and Canada. MRO is one of eight regional entities in North America operating under authority from regulators in the United States through a delegation agreement with the North American Electric Reliability Corporation (NERC) and in Canada through arrangements with provincial regulators. The primary purpose of MRO is to ensure compliance with reliability standards and perform regional assessments of the grid

  • 369

    Minimum generation

    The lowest level of production that a generating unit can maintain before it ceases to be cost-effective to keep online.

  • 370

    Mobile substation

    Transportable substation equipment designed for use as temporary infrastructure when a permanent substation is not practical or is out of service such as to provide temporary electric service at construction sites or emergency service.  

    Source: ESA Technical Working Group
  • 371

    Modular pumped hydroelectric electricity storage

    Acronym(s): MPHS

    Pumped hydroelectric storage systems with small or relatively small rated power and whose components.

    Source: ESA Technical Working Group
  • 372

    Municipal electric utility

    Acronym(s): muni

    A municipal corporation, municipal utility district, an irrigation district or a joint power authority furnishing electric services over its own transmission facilities, or furnishing electric service over its own or its members  

  • 373

    Must take resource

    An electric supply resource, including generation and power purchase agreements (PPAs) with “minimum energy take requirements” whose output must be purchased, without regard to the purchasing entity’s need for the output..  

    Source: ESA Technical Working Group