Electric Meter
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North American domestic analog ( Ferraris disk) electricity meter. Electricity meter with transparent plastic case (Israel) Electricity meter in West Bengal, IndiaAn electricity meter, electric meter, electrical meter, energy meter, or kilowatt-hour meter is a device that measures the amount of
electric energy Electrical energy is the energy transferred as electric charges move between points with different electric potential, that is, as they move across a potential difference. As electric potential is lost or gained, work is done changing the energy o ...
consumed by a residence, a
business Business is the practice of making one's living or making money by producing or Trade, buying and selling Product (business), products (such as goods and Service (economics), services). It is also "any activity or enterprise entered into for ...
, or an electrically powered device over a time interval.
Electric utilities An electric utility, or a power company, is a company in the electric power industry (often a public utility) that engages in electricity generation and Electricity retailing, distribution of electricity for sale generally in a regulated market. El ...
use electric meters installed at customers' premises for billing and monitoring purposes. They are typically calibrated in billing units, the most common one being the
kilowatt hour A kilowatt-hour ( unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a commo ...
(''kWh''). They are usually read once each billing period. When energy savings during certain periods are desired, some meters may measure demand, the maximum use of power in some interval. "Time of day" metering allows electric rates to be changed during a day, to record usage during peak high-cost periods and off-peak, lower-cost, periods. Also, in some areas meters have relays for
demand response Demand response is a change in the power consumption of an electric utility customer to better match the demand for power with the supply. Until the 21st century decrease in the cost of pumped storage and batteries, electric energy could not b ...
load shedding during peak load periods.


History

The earliest commercial uses of electric energy, in the 1880s, had easily predictable usage; billing was based on the number of lamps or motors installed in a building. However, as usage spread, and especially with the invention of pluggable appliances, it also became more variable, and the electric utilities sought a means to bill customers based on actual rather than estimated usage.


Direct current

An Aron type DC electricity meter showing that the calibration was in charge consumed rather than energy Many experimental types of meter were developed.
Thomas Edison Thomas Alva Edison (February11, 1847October18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These inventions, ...
at first worked on a
direct current Direct current (DC) is one-directional electric current, flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor (material), conductor such as a wire, but can also flow throug ...
(DC) electromechanical meter with a direct reading register, but instead developed an
electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase (typi ...
metering system, which used an
electrolytic cell An electrolytic cell is an electrochemical cell that utilizes an external source of electrical energy to force a chemical reaction that would otherwise not occur. The external energy source is a voltage applied between the cell's two electrodes; ...
to totalise current consumption. At periodic intervals the plates were removed and weighed, and the customer billed. The electrochemical meter was labor-intensive to read and not well received by customers. DC meters often measured
charge Charge or charged may refer to: Arts, entertainment, and media Films * ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * ''Charge'' (David Ford album) * ''Charge'' (Machel Montano album) * '' Charge!!'', an album by The Aqu ...
in ampere hours. Since the voltage of the supply should remain substantially constant, the reading of the meter was proportional to actual energy consumed. For example, if a meter recorded that 100 ampere hours had been consumed on a 200-volt supply, then 20 kilowatt-hours of energy had been supplied. left, A 'Reason' meter An early type of electrochemical meter used in the United Kingdom was the 'Reason' meter. This consisted of a vertically mounted glass structure with a mercury reservoir at the top of the meter. As current was drawn from the supply, electrochemical action transferred the mercury to the bottom of the column. Like all other DC meters, it recorded ampere hours. Once the mercury pool was exhausted, the meter became an open circuit. It was therefore necessary for the consumer to pay for a further supply of electricity, whereupon, the supplier's agent would unlock the meter from its mounting and invert it restoring the mercury to the reservoir and the supply. In practice the consumer would get the supply company's agent in before the supply ran out and pay only for the charge consumed as read from the scale. The agent would then reset the meter to zero by inverting it. In 1885
Ferranti Ferranti International PLC or simply Ferranti was a UK-based electrical engineering and equipment firm that operated for over a century, from 1885 until its bankruptcy in 1993. At its peak, Ferranti was a significant player in power grid system ...
offered a mercury motor meter with a register similar to gas meters; this had the advantage that the consumer could easily read the meter and verify consumption. The first accurate, recording electricity consumption meter was a DC meter by Hermann Aron, who patented it in 1883. Hugo Hirst of the British
General Electric Company The General Electric Company (GEC) was a major British industrial conglomerate involved in consumer and Arms industry, defence electronics, communications, and engineering. It was originally founded in 1886 as G. Binswanger and Company as an e ...
introduced it commercially into Great Britain from 1888. Aron's meter recorded the total charge used over time, and showed it on a series of clock dials.


Alternating current

The first specimen of the AC kilowatt-hour meter produced on the basis of Hungarian
Ottó Bláthy Ottó Titusz Bláthy (11 August 1860 – 26 September 1939) was a Hungarian electrical engineer. During his career he became the co-inventor of the modern electric transformer, the voltage regulator, the AC watt-hour meter, the turbo genera ...
's patent and named after him was presented by the
Ganz The Ganz Machinery Works Holding is a Hungarian holding company. Its products are related to rail transport, power generation, and water supply, among other industries. The original Ganz Works or Ganz ( or , ''Ganz companies'', formerly ''Ganz ...
Works at the Frankfurt Fair in the autumn of 1889, and the first induction kilowatt-hour meter was already marketed by the factory at the end of the same year. These were the first alternating-current watt-hour meters, known by the name of Bláthy-meters. The AC kilowatt hour meters used at present operate on the same principle as Bláthy's original invention. Student paper read on January 24, 1896 at the Students' Meeting.The Electrical engineer, Volume 5. (February, 1890) Also around 1889,
Elihu Thomson Elihu Thomson (March 29, 1853 – March 13, 1937) was an English-American engineer and inventor who was instrumental in the founding of major electricity, electrical companies in the United States, the United Kingdom and France. Early life He ...
of the American
General Electric General Electric Company (GE) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...
company developed a recording watt meter (watt-hour meter) based on an ironless commutator motor. This meter overcame the disadvantages of the electrochemical type and could operate on either alternating or direct current. In 1894 Oliver Shallenberger of the
Westinghouse Electric Corporation The Westinghouse Electric Corporation was an American manufacturing company founded in 1886 by George Westinghouse and headquartered in Pittsburgh, Pennsylvania. It was originally named "Westinghouse Electric & Manufacturing Company" and was ...
applied the induction principle previously used only in AC ampere hour meters to produce a watt-hour meter of the modern electromechanical form, using an
induction disk Induction or inductive may refer to: Biology and medicine * Labor induction (of birth) * Induction chemotherapy, in medicine * Enzyme induction and inhibition * General anaesthesia Chemistry * Induction period, slow stage of a reaction ...
whose rotational speed was made proportional to the power in the circuit. The Bláthy meter was similar to Shallenberger and Thomson meter in that they are two-phase motor meter. Although the induction meter would only work on alternating current, it eliminated the delicate and troublesome commutator of the Thomson design. Shallenberger fell ill and was unable to refine his initial large and heavy design, although he did also develop a polyphase version.


Units

Panel-mounted solid state electricity meter, connected to a 2 MVA electricity substation. Remote current and voltage sensors can be read and programmed remotely by modem and locally by infrared. The circle with two dots is the infrared port. Tamper-evident seals can be seen">infrared.html" ;"title="modem and locally by infrared">modem and locally by infrared. The circle with two dots is the infrared port. Tamper-evident seals can be seen The most common unit of measurement on the electricity meter is the
kilowatt hour A kilowatt-hour ( unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a commo ...
[''kWh''], which is equal to the amount of energy used by a load of one kilowatt over a period of one hour, or 3,600,000 joules. Some electricity companies use the SI megajoule instead. Demand is normally measured in watts, but averaged over a period, most often a quarter- or half-hour.
Reactive power In an electric circuit, instantaneous power is the time rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the ...
is measured in "thousands of
volt-ampere reactive The volt-ampere ( SI symbol: VA, sometimes V⋅A or V A) is the unit of measurement for apparent power in an electrical circuit. It is the product of the root mean square voltage (in volts) and the root mean square current (in amperes). ...
-hours", (kvarh). By convention, a "lagging" or inductive load, such as a motor, will have positive reactive power. A "leading", or capacitive load, will have negative reactive power. Volt-amperes measures all power passed through a distribution network, including reactive and actual. This is equal to the product of root-mean-square volts and amperes. Distortion of the electric current by loads is measured in several ways.
Power factor In electrical engineering, the power factor of an AC power system is defined as the ratio of the ''real power'' absorbed by the electrical load, load to the ''apparent power'' flowing in the circuit. Real power is the average of the instantaneou ...
is the ratio of resistive (or real) power to volt-amperes. A capacitive load has a leading power factor, and an inductive load has a lagging power factor. A purely resistive load (such as a filament lamp, heater or kettle) exhibits a power factor of 1. Current harmonics are a measure of distortion of the wave form. For example, electronic loads such as computer power supplies draw their current at the voltage peak to fill their internal storage elements. This can lead to a significant voltage drop near the supply voltage peak which shows as a flattening of the voltage waveform. This flattening causes odd harmonics which are not permissible if they exceed specific limits, as they are not only wasteful, but may interfere with the operation of other equipment. Harmonic emissions are mandated by law in EU and other countries to fall within specified limits. In addition to metering based on the amount of energy used, other types of metering are available. Meters which measured the amount of charge (
coulomb The coulomb (symbol: C) is the unit of electric charge in the International System of Units (SI). It is defined to be equal to the electric charge delivered by a 1 ampere current in 1 second, with the elementary charge ''e'' as a defining c ...
s) used, known as ampere hour meters, were used in the early days of electrification. These were dependent upon the supply voltage remaining constant for accurate measurement of energy usage, which was not a likely circumstance with most supplies. The most common application was in relation to special-purpose meters to monitor charge / discharge status of large batteries. Some meters measured only the length of time for which charge flowed, with no measurement of the magnitude of voltage or current being made. These are only suited for constant-load applications and are rarely used today.


Operation

Mechanism of induction meter. 1: Voltage coil: many turns of fine wire encased in plastic, connected in parallel with load. 2: Current coil: three turns of thick wire, connected in series with load. 3: Stator: concentrates and confines magnetic field. 4: Aluminum rotor disc. 5: rotor brake magnets. 6: spindle with worm gear. 7: display dials: the 1/10, 10 and 1000 dials rotate clockwise while the 1, 100 and 10000 dials rotate counterclockwise Electricity meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) to give
energy Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...
used (in
joules The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram- metre squared per second squared One joule is equal to the amount of work don ...
, kilowatt-hours etc.). Meters for smaller services (such as small residential customers) can be connected directly in-line between source and customer. For larger loads, more than about 200 ampere of load,
current transformer A current transformer (CT) is a type of transformer that reduces or multiplies alternating current (AC), producing a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or poten ...
s are used, so that the meter can be located somewhere other than in line with the service conductors. The meters fall into two basic categories, electromechanical and electronic.


Electromechanical

The most common type of electricity meter is the
electromechanical Electromechanics combine processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focus on the interaction of electrical and mechanical systems as a whole and how the two systems interact with each ...
watt-hour meter. On a
single-phase In electrical engineering, single-phase electric power (abbreviated 1φ) is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when loads ...
AC supply, the electromechanical induction meter operates through
electromagnetic induction Electromagnetic or magnetic induction is the production of an electromotive force, electromotive force (emf) across an electrical conductor in a changing magnetic field. Michael Faraday is generally credited with the discovery of induction in 1 ...
by counting the revolutions of a non-magnetic, but electrically conductive, metal disc which is made to rotate at a speed proportional to the power passing through the meter. The number of revolutions is thus proportional to the energy usage. The voltage coil consumes a small and relatively constant amount of power, typically around 2 watts which is not registered on the meter. The current coil similarly consumes a small amount of power in proportion to the square of the current flowing through it, typically up to a couple of watts at full load, which is registered on the meter. The disc is acted upon by two sets of
induction coil An induction coil or "spark coil" ( archaically known as an inductorium or Ruhmkorff coil after Heinrich Rühmkorff) is a type of transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 To create the ...
s, which form, in effect, a two phase
linear induction motor A linear induction motor (LIM) is an alternating current (AC), asynchronous linear motor that works by the same general principles as other induction motors but is typically designed to directly produce motion in a straight line. Characteristica ...
. One coil is connected in such a way that it produces a
magnetic flux In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the we ...
in proportion to the voltage and the other produces a magnetic flux in proportion to the current. The field of the voltage coil is delayed by 90 degrees, due to the coil's inductive nature, and calibrated using a lag coil. This produces eddy currents in the disc and the effect is such that a
force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...
is exerted on the disc in proportion to the product of the instantaneous current and instantaneous voltage. A
permanent magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, c ...
acts as an eddy current brake, exerting an opposing force proportional to the speed of rotation of the disc. The equilibrium between these two opposing forces results in the disc rotating at a speed proportional to the power or rate of energy usage. The disc drives a register mechanism which counts revolutions, much like the
odometer An odometer or odograph is an instrument used for measuring the distance traveled by a vehicle, such as a bicycle or car. The device may be electronic, mechanical, or a combination of the two (electromechanical). The noun derives from ancient Gr ...
in a car, in order to render a measurement of the total energy used. Different phase configurations use additional voltage and current coils. Three-phase electromechanical induction meter, metering 100 A 240/415 V supply. Horizontal aluminium rotor disc is visible in centre of meter The disc is supported by a spindle which has a
worm gear A worm drive is a gear train, gear arrangement in which a worm (which is a gear in the form of a Screw thread, screw) meshes with a worm wheel (which is similar in appearance to a spur gear). Its main purpose is to translate the motion of two p ...
which drives the register. The register is a series of dials which record the amount of energy used. The dials may be of the ''cyclometer'' type, an odometer-like display that is easy to read where for each dial a single digit is shown through a window in the face of the meter, or of the pointer type where a pointer indicates each digit. With the dial pointer type, adjacent pointers generally rotate in opposite directions due to the gearing mechanism. The amount of energy represented by one revolution of the disc is denoted by the symbol Kh which is given in units of watt-hours per revolution. The value 7.2 is commonly seen. Using the value of Kh one can determine their power consumption at any given time by timing the disc with a stopwatch. P = . Where: :: = time in seconds taken by the disc to complete one revolution, :: = power in watts. For example, if = 7.2 as above, and one revolution took place in 14.4 seconds, the power is 1800 watts. This method can be used to determine the power consumption of household devices by switching them on one by one. Most domestic electricity meters must be read manually, whether by a representative of the
power company The Power Company is a team of superheroes-for-hire in the DC Comics universe. The team, created by Kurt Busiek and Tom Grummett, first appeared in '' JLA'' #61 (February 2002). They subsequently starred in an eponymous series that ran for eigh ...
or by the customer. Where the customer reads the meter, the reading may be supplied to the power company by
telephone A telephone, colloquially referred to as a phone, is a telecommunications device that enables two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most ...
, post or over the
internet The Internet (or internet) is the Global network, global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a internetworking, network of networks ...
. The electricity company will normally require a visit by a company representative at least annually in order to verify customer-supplied readings and to make a basic safety check of the meter. In an induction type meter, creep is a phenomenon that can adversely affect accuracy, that occurs when the meter disc rotates continuously with potential applied and the load terminals open circuited. A test for error due to creep is called a creep test. Two standards govern meter accuracy, ANSI C12.20 for North America and IEC 62053.


Electronic

Solid state Danish-made electricity meter used in a home in the Netherlands Electronic meters display the energy used on an
LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...
or LED display, and some can also transmit readings to remote places. In addition to measuring energy used, some electronic meters can also record other parameters of the load and supply such as instantaneous and maximum rate of usage demands, voltages, power factor and
reactive power In an electric circuit, instantaneous power is the time rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the ...
used etc. They can also support time-of-day billing, for example, recording the amount of energy used during on-peak and off-peak hours. The meter has a power supply, a metering engine, a processing and communication engine (i.e. a
microcontroller A microcontroller (MC, uC, or μC) or microcontroller unit (MCU) is a small computer on a single integrated circuit. A microcontroller contains one or more CPUs (processor cores) along with memory and programmable input/output peripherals. Pro ...
), and other add-on modules such as a real time clock (RTC), a liquid crystal display, infra red communication ports/modules and so on. The metering engine is given the voltage and current inputs and has a voltage reference, samplers and quantisers followed by an analog to digital conversion section to yield the digitised equivalents of all the inputs. These inputs are then processed using a
digital signal processor A digital signal processor (DSP) is a specialized microprocessor chip, with its architecture optimized for the operational needs of digital signal processing. DSPs are fabricated on metal–oxide–semiconductor (MOS) integrated circuit chips. ...
to calculate the various metering parameters. The largest source of long-term errors in the meter is drift in the preamp, followed by the precision of the voltage reference. Both of these vary with temperature as well, and vary wildly when meters are outdoors. Characterising and compensating for these is a major part of meter design. The processing and communication section has the responsibility of calculating the various derived quantities from the digital values generated by the metering engine. This also has the responsibility of communication using various protocols and interface with other addon modules connected as slaves to it. RTC and other add-on modules are attached as slaves to the processing and communication section for various input/output functions. On a modern meter most if not all of this will be implemented inside the microprocessor, such as the RTC, LCD controller, temperature sensor, memory and analog to digital converters.


Communication methods

Remote meter reading is a practical example of
telemetry Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', 'far off', an ...
. It saves the cost of a human meter reader and the resulting mistakes, but it also allows more measurements, and remote provisioning. Many smart meters now include a switch to interrupt or restore service. Historically, rotating meters could report their metered information remotely, using a pair of
electrical contacts An electrical contact is an electrical circuit component found in electrical switches, relays, connectors and circuit breakers. Each contact is a piece of electrically conductive material, typically metal. When a pair of contacts touch, they ...
attached to a ''KYZ'' line. A KYZ interface is a Form C contact supplied from the meter. In a KYZ interface, the Y and Z wires are switch contacts, shorted to K for a measured amount of energy. When one contact closes the other opens to provide count accuracy security. Each contact change of state is considered one pulse. The frequency of pulses indicates the power demand. The number of pulses indicates energy metered. When incorporated into an electromechanical meter, the relay changes state with each full or half rotation of the meter disc. Each state change is called a "pulse." KYZ outputs were historically attached to "totaliser relays" feeding a "totaliser" so that many meters could be read all at once in one place. KYZ outputs are also the classic way of attaching electricity meters to
programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that ...
s,
HVAC Heating, ventilation, and air conditioning (HVAC ) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. ...
s or other control systems. Some modern meters also supply a contact closure that warns when the meter detects a demand near a higher electricity tariff, to improve
demand side management Energy demand management, also known as demand-side management (DSM) or demand-side response (DSR), is the modification of consumer demand for energy through various methods such as financial incentives and behavioral change through education. Us ...
. EN 62053-31 (formerly DIN 43864) defines the S0 interface, which is a galvanically isolated open collector output. Voltage and current are limited to 27 V and 27 mA, respectively. Each metered amount of electrical energy produces one impulse with a length of 32-100 ms. The meter constant (pulses per kWh) is programmable on some meters, but often fixed to 1000-10000 pulses per kWh. Other meters implement a similar pulse interface, but with an infrared LED instead of an electrical connection. The interface is also used on other kinds of meters, like water meters. Many meters designed for semi-automated reading have a
serial port A serial port is a serial communication Interface (computing), interface through which information transfers in or out sequentially one bit at a time. This is in contrast to a parallel port, which communicates multiple bits simultaneously in Pa ...
that communicates by
infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...
LED through the faceplate of the meter. In some multi-unit buildings, a similar protocol is used, but in a wired bus using a serial
current loop In electrical signalling an analog current loop is used where a device must be monitored or controlled remotely over a pair of conductors. Only one current level can be present at any time. A major application of current loops is the industry ...
to connect all the meters to a single plug. The plug is often near a more easily accessible point. In the European Union, the most common infrared and protocol is "FLAG", a simplified subset of mode C of IEC 61107. In the United States and Canada, the favored infrared protocol is ANSI C12.18. Some industrial meters use protocols for
programmable logic controller A programmable logic controller (PLC) or programmable controller is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that ...
s, like
Modbus Modbus (or MODBUS) is a client/server data communications protocol in the application layer. It was originally designed for use with programmable logic controllers (PLCs), but has become a ''de facto'' standardization, standard communication pr ...
or DNP3. One protocol proposed for this purpose is DLMS/COSEM which can operate over any medium, including serial ports. The data can be transmitted by
Zigbee Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and oth ...
,
Wi-Fi Wi-Fi () is a family of wireless network protocols based on the IEEE 802.11 family of standards, which are commonly used for Wireless LAN, local area networking of devices and Internet access, allowing nearby digital devices to exchange data by ...
,
telephone line A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or oth ...
s or over the power lines themselves. Some meters can be read over the internet. Other more modern protocols are also becoming widely used, like OSGP (Open Smart Grid Protocol). Electronic meters now also use low-power radio,
GSM The Global System for Mobile Communications (GSM) is a family of standards to describe the protocols for second-generation (2G) digital cellular networks, as used by mobile devices such as mobile phones and Mobile broadband modem, mobile broadba ...
,
GPRS General Packet Radio Service (GPRS), also called 2.5G, is a mobile data standard on the 2G cellular communication network's Global System for Mobile Communications, global system for mobile communications (GSM). Networks and mobile devices wit ...
,
Bluetooth Bluetooth is a short-range wireless technology standard that is used for exchanging data between fixed and mobile devices over short distances and building personal area networks (PANs). In the most widely used mode, transmission power is li ...
,
IrDA IrDA is a wireless standard designed for exchanging data using infrared (IR). Infrared ports for this purpose have been implemented in portable electronic devices such as mobile telephones, laptops, cameras, printers, and medical devices. The mai ...
, as well as
RS-485 RS-485, also known as TIA-485(-A) or EIA-485, is a standard, originally introduced in 1983, defining the electrical characteristics of drivers and receivers for use in serial communications systems. Electrical signaling is balanced, and Telecomm ...
wired link. The meters can store the entire usage profiles with timestamps and relay them at the click of a button. The demand readings stored with the profiles accurately indicate the load requirements of the customer. This
load profile In electrical engineering, a load profile is a graph of the variation in the electrical load versus time. A load profile will vary according to customer type (typical examples include residential, commercial and industrial), temperature and hol ...
data is processed at the utilities for billing and planning purposes. ''AMR'' ( Automatic Meter Reading) and ''RMR'' (Remote Meter Reading) describe various systems that allow meters to be checked remotely, without the need to send a meter reader. An electronic meter can transmit its readings by telephone line or radio to a central billing office.


Monitoring and billing methods


Commercial uses

Large commercial and industrial premises may use electronic meters which record power usage in blocks of half an hour or less. This is because most
electricity grid An electrical grid (or electricity network) is an interconnected network for electricity delivery from producers to consumers. Electrical grids consist of power stations, electrical substations to step voltage up or down, electric power trans ...
s have demand surges throughout the day, and the power company may wish to give price incentives to large customers to reduce demand at these times. These demand surges often correspond to meal times or, famously, to advertisements interrupting popular
television programme A television show, TV program (), or simply a TV show, is the general reference to any content produced for viewing on a television set that is broadcast via over-the-air, satellite, and cable, or distributed digitally on streaming platf ...
s, such as the TV pickup.


Home energy monitoring

A potentially powerful means to reduce household energy consumption is to provide convenient real-time feedback to users so they can change their energy using behaviour. Recently, low-cost energy feedback displays have become available, that may be able to measure energy (Watt-hours), momentary power (wattage), and may additionally be able to measure the MAINS voltage, current, uptime,
apparent power In an electric circuit, instantaneous power is the time rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the d ...
, capturing peak wattage and peak current, and have a manually set clock. The display may indicate the power consumption over the week graphically. A study using a consumer-readable meter in 500 Ontario homes by '' Hydro One'' showed an average 6.5% drop in total electricity use when compared with a similarly sized control group. ''Hydro One'' subsequently offered free power monitors to 30,000 customers based on the success of the pilot. Projects such as Google PowerMeter, take information from a smart meter and make it more readily available to users to help encourage conservation. Plug-in electricity meters (or plug load meters) measure energy used by individual appliances. There are a variety of models available on the market today but they all work on the same basic principle. The meter is plugged into an outlet, and the appliance to be measured is plugged into the meter. Such meters can help in
energy conservation Energy conservation is the effort to reduce wasteful energy consumption by using fewer energy services. This can be done by using energy more effectively (using less and better sources of energy for continuous service) or changing one's behavi ...
by identifying major energy users, or devices that consume excessive
standby power Standby power, also called vampire power, vampire draw, phantom load, ghost load, or leaking electricity, refers to how certain electronic and electrical appliances consume electricity while they are not actively in use, but which are still ...
. Web resources can also be used, if an estimate of the power consumption is enough for the research purposes. A power meter can often be borrowed from the local power authorities or a local public library.


Multiple tariff

Electricity retailers may wish to charge customers different tariffs at different times of the day to better reflect the costs of generation and transmission. Since it is typically not cost effective to store significant amounts of electricity during a period of low demand for use during a period of high demand, costs will vary significantly depending on the time of day. Low cost generation capacity (baseload) such as nuclear can take many hours to start, meaning a surplus in times of low demand, whereas high cost but flexible generating capacity (such as gas turbines) must be kept available to respond at a moment's notice (spinning reserve) to peak demand, perhaps being used for a few minutes per day, which is very expensive. Some multiple tariff meters use different tariffs for different amounts of demand. These are usually industrial meters. Domestic variable-rate meters generally permit two to three tariffs ("peak", "off-peak" and "shoulder") and in such installations a simple electromechanical time switch may be used. Historically, these have often been used in conjunction with electrical storage heaters or hot water storage systems. Multiple tariffs are made easier by time of use (TOU) meters which incorporate or are connected to a
time switch A time switch (also called a timer switch, or simply timer) is a device that operates an electric switch controlled by a timer. Intermatic introduced its first time switch in 1945, which was used for "electric signs, store window lighting, apartm ...
and which have multiple registers. Switching between the tariffs may happen via
ripple control Load management, also known as demand-side management (DSM), is the process of Load balancing (electrical power), balancing the supply of electricity on the network with the electrical load by adjusting or controlling the load rather than the pow ...
, or via a radio-activated switch. In principle, a sealed time switch can also be used, but is considered more vulnerable to tampering to obtain cheaper electricity. Economy 7 Meter and Teleswitcher Radio-activated switching is common in the UK, with a nightly data signal sent within the longwave carrier of
BBC Radio 4 BBC Radio 4 is a British national radio station owned and operated by the BBC. The station replaced the BBC Home Service on 30 September 1967 and broadcasts a wide variety of spoken-word programmes from the BBC's headquarters at Broadcasti ...
, 198 kHz. The time of off-peak charging is usually seven hours between midnight and 7:00am GMT/BST, and this is designed to power storage heaters and
immersion heater Electric heating is a process in which electrical energy is converted directly to heat energy. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that convert ...
s. In the UK, such tariffs are typically branded '' Economy 7'', ''White Meter'' or ''Dual-Rate''. The popularity of such tariffs has declined in recent years, at least in the domestic market, because of the (perceived or real) deficiencies of storage heaters and the comparatively much lower cost of
natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...
per kWh (typically a factor of 3-5 times lower). Nevertheless, a sizeable number of properties do not have the option of gas, with many in rural areas being outside the gas supply network, and others being expensive upfront to upgrade to a radiator system. An Economy 10 meter is also available, which gives 10 hours of cheap off-peak electricity spread out over three timeslots throughout a 24-hour period. This allows multiple top-up boosts to storage heaters, or a good spread of times to run a wet electric heating system on a cheaper electricity rate. Most meters using '' Economy 7'' switch the entire electricity supply to the cheaper rate during the 7 hour night time period, not just the storage heater circuit. The downside of this is that the daytime rate per kWh is significantly higher, and that standing charges are sometimes higher. For example, as of July 2017, normal ("single rate") electricity costs 17.14p per kWh in the London region on the standard default tariff for EDF Energy (the post-privatisation incumbent electricity supplier in London), with a standing charge of 18.90p per day. The equivalent Economy 7 costs are 21.34p per kWh during the peak usage period with 7.83p per kWh during the off-peak usage period, and a standing charge of 18.90p per day. Timer switches installed on
washing machine A washing machine (laundry machine, clothes washer, washer, or simply wash) is a machine designed to laundry, launder clothing. The term is mostly applied to machines that use water. Other ways of doing laundry include dry cleaning (which uses ...
s, tumble dryers,
dishwasher A dishwasher is a machine that is used to clean dishware, cookware, and cutlery automatically. Unlike dishwashing, manual dishwashing, which relies on physical scrubbing to remove soiling, the mechanical dishwasher cleans by spraying hot wat ...
s and
immersion heater Electric heating is a process in which electrical energy is converted directly to heat energy. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical device that convert ...
s may be set so that they only switch on during the off-peak usage period.


Smart meters

Smart meters go a step further than simple AMR ( automatic meter reading). They offer additional functionality including a real-time or near real-time reads,
power outage A power outage, also called a blackout, a power failure, a power blackout, a power loss, a power cut, or a power out is the complete loss of the electrical power network supply to an end user. There are many causes of power failures in an el ...
notification, and power quality monitoring. They allow price setting agencies to introduce different prices for consumption based on the time of day and the season. Another type of smart meter uses nonintrusive load monitoring to automatically determine the number and type of appliances in a residence, how much energy each uses and when. This meter is used by electric utilities to do surveys of energy use. It eliminates the need to put timers on all of the appliances in a house to determine how much energy each uses.


Prepayment meters

Prepayment meter and magnetic stripe tokens, from a rented accommodation in the UK. The button labelled A displays information and statistics such as current tariff and remaining credit. The button labelled B activates a small amount of emergency credit should the customer run out file:Smart card prepaid electric meter.jpg, A digital smart card type prepaid meter file:London electricity keymeter key.jpg, A prepayment key The standard business model of electricity retailing involves the electricity company billing the customer for the amount of energy used in the previous month or quarter. In some countries, if the retailer believes that the customer may not pay the bill, a prepayment meter may be installed. This requires the customer to make advance payment before electricity can be used. If the available credit is exhausted then the supply of electricity is cut off by a
relay A relay Electromechanical relay schematic showing a control coil, four pairs of normally open and one pair of normally closed contacts An automotive-style miniature relay with the dust cover taken off A relay is an electrically operated switc ...
. In the UK, mechanical prepayment coin meters used to be common, both in private rented accommodation and residential customers of the electricity boards, the nationalised electricity sector. Disadvantages of these included the need for regular visits to remove the cash, and risk of theft of the cash in the meters by both customers and burglars. The first automated pre-payment meters were introduced by London Electricity, in conjunction with the Schlumberger Metering based in Felixstowe, UK. They were initially called Key Meters and later renamed Budget Meters. They avoided the 60,000 disconnections for non-payment per annum and the many disadvantages of cash prepayment. They were also popular with customers who wanted a convenient payment method, especially in short term tenancies. Well over 1 million such meters were installed across the UK in the first few years after introduction. Modern solid-state electricity meters, in conjunction with
smart card A smart card (SC), chip card, or integrated circuit card (ICC or IC card), is a card used to control access to a resource. It is typically a plastic credit card-sized card with an Embedded system, embedded integrated circuit (IC) chip. Many smart ...
s, have removed these disadvantages and such meters are commonly used for customers considered to be a poor
credit risk Credit risk is the chance that a borrower does not repay a loan In finance, a loan is the tender of money by one party to another with an agreement to pay it back. The recipient, or borrower, incurs a debt and is usually required to pay ...
. In the UK, customers can use organisations such as the
Post Office Limited Post Office Limited, formerly Post Office Counters Limited and commonly known as the Post Office, is a state-owned retail post office company in the United Kingdom that provides a wide range of postal and non-postal related products including po ...
or PayPoint network, where rechargeable tokens (Quantum cards for natural gas, or plastic "keys" for electricity) can be loaded with whatever money the customer has available. In
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
,
Sudan Sudan, officially the Republic of the Sudan, is a country in Northeast Africa. It borders the Central African Republic to the southwest, Chad to the west, Libya to the northwest, Egypt to the north, the Red Sea to the east, Eritrea and Ethiopi ...
and
Northern Ireland Northern Ireland ( ; ) is a Countries of the United Kingdom, part of the United Kingdom in the north-east of the island of Ireland. It has been #Descriptions, variously described as a country, province or region. Northern Ireland shares Repub ...
prepaid meters are recharged by entering a unique, encoded twenty digit number using a keypad. This makes the tokens, which may be electronically delivered or printed on a slip of paper at point of purchase, very cheap to produce. Around the world, experiments are going on, especially in developing countries, to test pre-payment systems. In some cases, prepayment meters have not been accepted by customers. There are various groups, such as the Standard Transfer Specification (
STS STS, or sts, may refer to: Medicine * Secondary traumatic stress, a condition which leads to a diminished ability to empathize * Sequence-tagged site, a gene-reference in genomics * Soft-tissue sarcoma * Staurosporine, an antibiotic * STS (gene ...
) association, which promote common standards for prepayment metering systems across manufacturers. Prepaid meters using the STS standard are used in many countries.


Time of day metering

Time of Day metering (TOD), also known as Time of Usage (TOU) or Seasonal Time of Day (SToD), metering involves dividing the day, month and year into tariff slots and with higher rates at peak load periods and low tariff rates at off-peak load periods. While this can be used to automatically control usage on the part of the customer (resulting in automatic load control), it is often simply the customer's responsibility to control his own usage or pay accordingly (voluntary load control). This also allows the
utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...
to plan their transmission infrastructure appropriately. See also Demand-side Management (DSM). TOD metering normally splits rates into an arrangement of multiple segments including on-peak, off-peak, mid-peak or shoulder, and critical peak. A typical arrangement is a peak occurring during the day (non-holiday days only), such as from 1 pm to 9 pm Monday through Friday during the summer and from 6:30 am to 12 noon and 5 pm to 9 pm during the winter. More complex arrangements include the use of critical peaks that occur during high demand periods. The times of peak demand/cost will vary in different markets around the world. Large commercial users can purchase power by the hour using either forecast pricing or real-time pricing. Some utilities allow residential customers to pay hourly rates, such as in Illinois, which uses day ahead pricing.


Power export metering

Many electricity customers are installing their own electricity generating equipment, whether for reasons of economy, redundancy or environmental reasons. When a customer is generating more electricity than required for his own use, the surplus may be exported back to the
power grid ''Power Grid'' is the English-language version of the second edition of the multiplayer German-style board game ''Funkenschlag'', designed by Friedemann Friese and first released in 2004. ''Power Grid'' was released by Rio Grande Games. I ...
. Customers that generate back into the "grid" usually must have special equipment and safety devices to protect the grid components (as well as the customer's own) in case of faults (electrical short circuits) or maintenance of the grid (say voltage on a downed line coming from an exporting customers facility). This exported energy may be accounted for in the simplest case by the meter running backwards during periods of net export, thus reducing the customer's recorded energy usage by the amount exported. This in effect results in the customer being paid for his/her exports at the full retail price of electricity. Unless equipped with a ratchet or equivalent, a standard meter will accurately record power flow in each direction by simply running backwards when power is exported. Where allowed by law, utilities maintain a profitable margin between the price of energy delivered to the consumer and the rate credited for consumer-generated energy that flows back to the grid. Lately, upload sources typically originate from renewable sources (e.g.,
wind turbine A wind turbine is a device that wind power, converts the kinetic energy of wind into electrical energy. , hundreds of thousands of list of most powerful wind turbines, large turbines, in installations known as wind farms, were generating over ...
s,
photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...
cells), or
gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...
or steam
turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...
s, which are often found in
cogeneration Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time. Cogeneration is a more efficient use of fuel or heat, because otherwise- wasted heat from elec ...
systems. Another potential upload source that has been proposed is
plug-in hybrid A plug-in hybrid electric vehicle (PHEV) or simply plug-in hybrid is a type of hybrid electric vehicle equipped with a rechargeable battery pack that can be directly replenished via a charging cable plugged into an external electric power so ...
car batteries (
vehicle-to-grid Vehicle-to-grid (V2G) describes a system in which plug-in electric vehicles (PIEVs) sell demand response services to the electrical grid. Such services are either backfeeding electricity to the grid, or reducing the rate of charge from the gri ...
power systems). This requires a "
smart grid The smart grid is an enhancement of the 20th century electrical grid, using two-way communications and distributed so-called intelligent devices. Two-way flows of electricity and information could improve the delivery network. Research is main ...
," which includes meters that measure electricity via communication networks that require remote control and give customers timing and pricing options. Vehicle-to-grid systems could be installed at workplace
parking lot A parking lot or car park (British English), also known as a car lot, is a cleared area intended for parking vehicles. The term usually refers to an area dedicated only for parking, with a durable or semi-durable surface. In most jurisdi ...
s and garages and at
park and ride A park and ride, also known as incentive parking or a commuter lot, is a parking lot with public transport connections that allows commuters and other people heading to city centres to leave their vehicles and transfer to a bus, Rail transport, r ...
s and could help drivers charge their batteries at home at night when off-peak power prices are cheaper, and receive bill crediting for selling excess electricity back to the grid during high-demand hours.


Location

Current transformers used as part of metering equipment for three-phase 400 A electricity supply. The fourth neutral wire does not require a current transformer because current cannot flow in the neutral without also flowing in metered phase wires. ( Blondel's theorem) file:Dunkin donuts electric power meter in framingham ma shot by brian katt with a canon digital rebel in June of 2006.JPG, A commercial power meter file:Electricity meters in India.JPG, Electricity meters placed outside the homes of residents in a common place, which is accessible only for the department staff and concerned residents file:2008-08-12 Technician disconnecting electricity for nonpayment.jpg">A Duke Energy technician removes the tamper-proof seal from an electricity meter at a residence in Durham, North Carolina The location of an electricity meter varies with each installation. Possible locations include on a
utility pole A utility pole, commonly referred to as a transmission pole, telephone pole, telecommunication pole, power pole, hydro pole, telegraph pole, or telegraph post, is a column or post used to support overhead power lines and various other public util ...
serving the property, in a street-side cabinet (meter box) or inside the premises adjacent to the
consumer unit A consumer is a person or a group who intends to order, or use purchased goods, products, or services primarily for personal, social, family, household and similar needs, who is not directly related to entrepreneurial or business activities. Th ...
/
distribution board Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ...
. Electricity companies may prefer external locations as the meter can be read without gaining access to the premises but external meters may be more prone to
vandalism Vandalism is the action involving deliberate destruction of or damage to public or private property. The term includes property damage, such as graffiti and defacement directed towards any property without permission of the owner. The t ...
.
Current transformer A current transformer (CT) is a type of transformer that reduces or multiplies alternating current (AC), producing a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or poten ...
s permit the meter to be located remotely from the current-carrying conductors. This is common in large installations. For example, a substation serving a single large customer may have metering equipment installed in a cabinet, without bringing heavy cables into the cabinet.


Customer drop and metering equation

Since electrical standards vary in different regions, "customer drops" from the grid to the customer also vary depending on the standards and the type of installation. There are several common types of connections between a grid and a customer. Each type has a different ''metering equation.'' Blondel's theorem states that for any system with N current-carrying conductors, that N-1 measuring elements are sufficient to measure electrical energy. This indicates that different metering is needed, for example, for a three-phase three-wire system than for a three-phase four-wire (with neutral) system. In Europe, Asia, Africa and most other locations,
single phase In electrical engineering, single-phase electric power (abbreviated 1φ) is the distribution of alternating current electric power using a system in which all the voltages of the supply vary in unison. Single-phase distribution is used when load ...
is common for residential and small commercial customers. Single phase distribution is less-expensive, because one set of transformers in a substation normally serve a large area with relatively high voltages (usually 230 V) and no local transformers. These have a simple metering equation:
Watt The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...
s =
volts The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). Definition One volt is defined as the electric potential between two point ...
x amps, with volts measured from the neutral to the phase wire. In the United States, Canada, and parts of Central and South America similar customers are normally served by three-wire single phase. Three-wire single-phase requires local transformers, as few as one per ten residences, but provides lower, safer voltages at the socket (usually 120 V), and provides two voltages to customers: neutral to phase (usually 120 V), and phase to phase (usually 240 V). Additionally, three-wire customers normally have neutral wired to the zero side of the generator's windings, which gives earthing that can be easily measured to be safe. These meters have a metering equation of Watts = 0.5 x volts x (amps of phase A − amps of phase B), with volts measured between the phase wires. Industrial power is normally supplied as three phase power. There are two forms: three wire, or four wire with a system neutral. In "three wire" or "three wire delta", there is no neutral but an earth ground is the safety ground. The three phases have voltage only relative to each other. This distribution method has one fewer wire, is less expensive, and is common in Asia, Africa, and many parts of Europe. In regions that mix residences and light industry, it is common for this to be the only distribution method. A meter for this type normally measures two of the windings relative to the third winding, and adds the watts. One disadvantage of this system is that if the safety earth fails, it is difficult to discover this by direct measurement, because no phase has a voltage relative to earth. In the four-wire three-phase system, sometimes called "four-wire wye", the safety ground is connected to a neutral wire that is physically connected to the zero-voltage side of the three windings of the generator or transformer. Since all power phases are relative to the neutral in this system, if the neutral is disconnected, it can be directly measured. In the United States, the National Electrical Code requires neutrals to be of this type. In this system, power meters measure and sum all three phases relative to the neutral. In North America, it is common for electricity meters to plug into a standardised socket outdoors, on the side of a building. This allows the meter to be replaced without disturbing the wires to the socket, or the occupant of the building. Some sockets may have a bypass while the meter is removed for service. The amount of electricity used without being recorded during this small time is considered insignificant when compared to the inconvenience which might be caused to the customer by cutting off the electricity supply. Most electronic meters in North America use a serial protocol, ANSI C12.18. In many other countries the supply and load terminals are in the meter housing itself. Cables are connected directly to the meter. In some areas the meter is outside, often on a utility pole. In others, it is inside the building in a niche. If inside, it may share a data connection with other meters. If it exists, the shared connection is often a small plug near the post box. The connection is often EIA-485 or infrared with a serial protocol such as IEC 62056. In 2014, networking to meters is rapidly changing. The most common schemes seem to combine an existing national standard for data (e.g. ANSI C12.19 or IEC 62056) operating via the
Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP ...
with a small circuit board for powerline communication, or a digital radio for a
mobile phone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This rad ...
network, or an
ISM band The ISM radio bands are portions of the radio spectrum reserved internationally for ''industrial, scientific, and medical'' (ISM) purposes, excluding applications in telecommunications. Examples of applications for the use of radio frequency (RF ...
.


Accuracy

Electricity meters are required to register the energy consumed within an acceptable degree of accuracy. Any significant error in the registered energy can represent a loss to the electricity supplier, or the consumer being over billed. The accuracy is generally laid down in statute for the location in which the meter is installed. Statutory provisions may also specify a procedure to be followed should the accuracy be disputed. For the United Kingdom, any installed electricity meter is required to accurately record the consumed energy, but it is permitted to under-read by 3.5%, or over-read by 2.5%. Disputed meters are initially verified with a check meter operating alongside the disputed meter. The final resort is for the disputed meter to be fully tested both in the installed location and at a specialist calibration laboratory. Approximately 93% of disputed meters are found to be operating satisfactorily. A refund of electricity paid for, but not consumed (but not vice versa) will only be made if the laboratory is able to estimate how long the meter has been misregistering. This contrasts with gas meters where if a meter is found to be under reading, it is assumed that it has under read for as long as the consumer has had a gas supply through it. Any refund due is limited to the previous six years.


Tampering and security

Meters can be manipulated to make them under-register, effectively allowing power use without paying for it. Power companies often install remote-reporting meters specifically to enable remote detection of tampering, and specifically to discover energy theft. The change to smart power meters is useful to stop energy theft. When tampering is detected, the normal tactic, legal in most areas of the United States, is to switch the subscriber to a " tampering" tariff charged at the meter's maximum designed current. At US $0.095/kWh, a standard residential 50 A meter causes a legally collectible charge of about US$5,000.00 per month. Meter readers are trained to spot signs of tampering, and with crude mechanical meters, the maximum rate may be charged each billing period until the tamper is removed, or the service is disconnected. A common method of tampering on mechanical disk meters is to attach
magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
s to the outside of the meter. Strong magnets saturate the magnetic fields in the meter so that the motor portion of a mechanical meter does not operate. Lower power magnets can add to the drag resistance of the internal disk resistance magnets. Magnets can also saturate current transformers or power-supply transformers in electronic meters, though countermeasures are common. Some combinations of capacitive and inductive load can interact with the coils and mass of a rotor and cause reduced or reverse motion. All of these effects can be detected by the electric company, and many modern meters can detect or compensate for them. The owner of the meter normally secures the meter against tampering. Revenue meters' mechanisms and connections are sealed. Meters may also measure VAR-hours (the reflected load), neutral and DC currents (elevated by most electrical tampering), ambient magnetic fields, etc. Even simple mechanical meters can have mechanical flags that are dropped by magnetic tampering or large DC currents. Newer computerised meters usually have counter-measures against tampering. AMR (Automated Meter Reading) meters often have sensors that can report opening of the meter cover, magnetic anomalies, extra clock setting, glued buttons, inverted installation, reversed or switched phases etc. Some tampers bypass the meter, wholly or in part. Safe tampers of this type normally increase the neutral current at the meter. Most split-phase residential meters in the United States are unable to detect neutral currents. However, modern tamper-resistant meters can detect and bill it at standard rates. Disconnecting a meter's neutral connector is unsafe because shorts can then pass through people or equipment rather than a metallic ground to the generator or earth. A
phantom loop In telecommunications and electrical engineering, a phantom circuit is an electrical circuit derived from suitably arranged wires with one or more conductive paths being a circuit in itself and at the same time acting as one conductor of another ci ...
connection via an earth ground is often much higher resistance than the metallic neutral connector. Even if an earth ground is safe, metering at the substation can alert the operator to tampering. Substations, inter-ties, and transformers normally have a high-accuracy meter for the area served. Power companies normally investigate discrepancies between the total billed and the total generated, in order to find and fix power distribution problems. These investigations are an effective method to discover tampering. Power thefts in the United States are often connected with indoor marijuana grow operations. Narcotics detectives associate abnormally high power usage with the lighting such operations require. Indoor marijuana growers aware of this are particularly motivated to steal electricity simply to conceal their usage of it.


Global standards for Electricity Metering

Electricity meters are governed by various standards worldwide to ensure accuracy, reliability, and interoperability. These standards vary by region and are often based on national or international regulations. Below are the key standards used in different regions. European Standards :In Europe, electricity meters are primarily regulated under the Measuring Instruments Directive (MID), established by the European Union. MID ensures that electricity meters meet specific technical and operational criteria for accurate billing. Key standards include: :* EN 50470-1 to EN 50470-3: These standards specify general requirements, particular requirements, and tests for active energy meters. :* IEC 62052 and IEC 62053 series: Commonly applied for the functional and accuracy performance of electricity meters. American Standards :In the United States, the standards are developed by the American National Standards Institute (ANSI) and the Institute of Electrical and Electronics Engineers (IEEE). Key standards include: :*ANSI C12 Series: Covering meter accuracy, testing, and performance for residential, commercial, and industrial meters. :*IEEE 1708: Provides guidelines for testing the cybersecurity of smart meters. Chinese Standards :In China, electricity meter standards are governed by the China National Standards (GB), which align with international practices but also reflect specific local requirements: :*GB/T 17215: Sets the requirements for static electricity meters for active energy. :*DL/T 645: Specifies the communication protocol for multi-function electricity meters, ensuring interoperability. Australian Standards :In Australia, electricity meters adhere to the standards set by Standards Australia and the National Measurement Institute (NMI): :*AS 62052.11 and AS 62053.21: Align with IEC standards for general requirements and accuracy classes of electricity meters. :*NMI M 6: Specifies the metrological requirements for electricity meters used for billing.


Regulation and legislation

Following the
deregulation Deregulation is the process of removing or reducing state regulations, typically in the economic sphere. It is the repeal of governmental regulation of the economy. It became common in advanced industrial economies in the 1970s and 1980s, as a ...
of electricity supply markets in many countries, the company responsible for an electricity meter may not be obvious. Depending on the arrangements in place, the meter may be the property of the meter Operator, electricity distributor, the
retailer Retail is the sale of goods and services to consumers, in contrast to wholesaling, which is the sale to business or institutional customers. A retailer purchases goods in large quantities from manufacturers, directly or through a wholesal ...
or for some large users of electricity the meter may belong to the customer. The company responsible for reading the meter may not always be the company which owns it. Meter reading is now sometimes subcontracted and in some areas the same person may read
gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...
,
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
and electricity meters at the same time. The introduction of advanced meters in residential areas has produced additional privacy issues that may affect ordinary customers. These meters are often capable of recording energy usage every 15, 30 or 60 minutes. Some meters have one or two IR LEDs on the front: one used for testing and which acts as the equivalent of the timing mark on the older mechanical meters and the other as part of a two-way IR communications port for reading / programming the meter. These IR LEDs are visible with some night vision viewers and certain video cameras that are capable of sensing IR transmissions. These can be used for surveillance, revealing information about peoples' possessions and behaviour. For instance, it can show when the customer is away for extended periods. Nonintrusive load monitoring gives even more detail about what appliances people have and their living and use patterns. A more detailed and recent analysis of this issue was performed by the Illinois Security Lab.


See also

* Energy management software * Energy monitoring and targeting * Meter operator * Utility submeter * Zellweger off-peak *
Multimeter A multimeter (also known as a multi-tester, volt-ohm-milliammeter, volt-ohmmeter or VOM, avometer or ampere-volt-ohmmeter) is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, elec ...


Notes


References

*"Handbook for Electricity Metering" by The Edison Electric Institute


External links

* {{Authority control Electrical instruments