Marginal Cost: The cost of producing one additional unit of a particular product or service.

Market-Based Pricing: Electric service prices determined in an open market system of supply and demand under which the price is set solely by agreement as to what a buyer will pay and a seller will accept. Such prices could recover less or more than full costs, depending upon what the buyer and seller see as their relevant opportunities and risks.

Master-metered: The system by which multi-unit buildings or mobile home parks are connected to a single meter. The master-meter holder receives a single bill from the utility and collects from tenants individually. The utility has no liability for repairs or maintenance beyond the master meter.

MAS – Multiple Address System: A communications system serving a minimum of four remote stations.

Maximum Rates: The ceiling set by the Commission on what household goods moving and storage companies can charge. Such carriers may charge no more than these rates but may reduce their rates to respond to competition.

MB – Megabyte or Meg.: A measure of storage capacity equal to about one million bytes or about 500 typed pages.

Mbps – Megabits per second: 1,000,000 bits per second. A measure of how fast data can be transmitted.

Mbps: megabytes per second.

MCF: One thousand cubic feet

MCP – Market Clearing Price: The price at which supply equals demand for the Day Ahead and/or Hour Ahead Markets.

Measured Telephone Rates: A telephone rate plan by which customers pay for the number of calls and the duration of each call. In California , most businesses are already on such a plan and, in most areas, residential customers may choose the service.

Measured Telephone Service: An accounting procedure which allows a utility to record expenses and/or revenues off-book for a set period of time during which, because of such changes as fuel cost increases, those expenses or costs differ from its projected figures for that period of time; the utility's accounts may be balanced, that is, increased or decreased, in its next formal rate increase or other proceeding.

Memory: The part of a computer where information is stored.

Menu: A list of options (e.g., EDIT, PRINT) in computer processing displayed on a video screen, with selection made on a keyboard or by pointing a special device (the mouse) at the item listed on the screen.

Mercalli: A standard scale of relative measurement of earthquake intensity.

Meter Retrofit Programs: Programs targeted toward un-metered homes and businesses that either install a new meter or repair an existing meter to provide for billing based on volume of use.

Mhz: megahertz.

MHP: Mobile Home Park .

Minimum Rates: Covering highway carriers, these charges are the minimum set by the Commission that a carrier can charge for transporting materials and are published in minimum rate tariffs (MRTs). It is unlawful to charge below these rates, unless the Commission approves a deviation.

MMBtu: Million British Thermal Units (equals on Dth).

MMcf/d: Million cubic feet per day (also MMCfd).

MMth: Million therms.

Modem –Modular-Demodulator: Hardware that allows a computer to communicate with other computers through ordinary telephone lines (if they also have modems attached).

MOD-POD – Modified Presiding Officer's Decision: Issued by PUC Administrative Law Judges (ALJ). In certain proceeding the ALJ issues a ruling called a POD. If that decision is modified, it becomes a MOD-POD.

Monitor: Computer Screen

Motor Transportation Broker: Any person or corporation arranging or offering to arrange for compensation for the hauling of property by any motor carrier over California highways.

MOU - Memoranda of Understanding: A formalized, legal understanding between parties to enter into an agreement or create stipulations in proceedings or cases.

Mountain Front Recharge: Natural recharge that occurs at the base of the mountains because of rainfall or snow melt at higher elevations.

Mouse: A peripheral device that is connected to a computer allowing the operator to move around the screen without the aid of the keyboard.

MSA – Metropolitan Statistical Area: The MSA is comprised of one of more counties and of a high degree of social and economic integration as defined by the U.S. Census Bureau.

MSO – Multiple System Operator: A company that operates more than one cable TV system.

MUD – Multi-User Dimension: This term refers to users who connect to each other via a host computer.

MUNI – Municipally-Owned Utility: A utility owned and operated by a city or county. The PUC does not have regulatory authority over munis.

Municipal Water Use: All non-irrigation uses of water supplied by a city, town, private water company or irrigation district.

MW – Megawatt: One million watts or 1,000 kW.

MWh: Megawatt-hours.