Third-party access to the network (ATR): Access to the network by those who are not owners of the transport and distribution network.

Connection: It is the part of the mains piping that goes from the distribution network to the mains shut-off key, including the latter. It is not part of the consumer installation.

Underground storage: This is made up of artificially created gas fields in underground formations suitable for this purpose, in order to match gas supplies to seasonal demand.

High pressure: A pressure in excess of 4 bar, effective (or relative)

Ampere (Amp): Unit of electric current.

Control cabinet: This is the set of gas pressure regulation equipment when it is housed inside a cabinet.


Back up: Backup power plants guarantee electricity supply when other production sources stop generating electricity. In Spain, coal and combined cycle thermal power plants act as backup power plants. These technologies are able to become fully operational in a short period of time when non-manageable renewable energies stop feeding energy into the network.

Low pressure: In natural gas distribution activity, this corresponds to values less than or equal to 0.05 effective (or relative) bar.

BCM: Billion Cubic Metres, which is equivalent to one thousand million cubic metres. A unit of measurement usually used for natural gas.

Earnings before interest and taxes: Company profit/loss calculated as total operating income minus total operating expense. A term that is often shortened to EBIT.

Net Profit after Taxes: Final company profit/loss calculated as operating profit/loss minus financial expense minus corporation tax.

Biogas: This is a type of gas (made up of carbon dioxide equivalent, carbon monoxide and methane) that is generated through fermentation of organic waste, mainly in landfills, agricultural waste or in wastewater. Once it has been collected, it can be used to generate electricity.

Biomass: Organic material obtained from biological processes, whether spontaneous or induced, that is used as an energy source. In Spain, it is mainly produced in the forest industry and is used both in a domestic environment (as firewood) and in thermal and electrical production

Pumping: Hydraulic technology that allows energy to be stored (in the form of water) during times of lower electricity demand and kilowatt hours to be generated at times of peak consumption or of electricity system demand. Pumping plants transport water from a lower reservoir to a higher one, where it is converted into electricity again in a hydroelectric plant. Thanks to the way they operate, pumping stations help optimise the electricity system and perfectly complement non-manageable renewable generation.

Social tariff: Tariff set by the government with a discount on PVPC, to protect vulnerable consumers.


Centralised Boiler: Installation through which a property's supply points are connected to a Central Boiler.

Piping: This is the set of pipelines and accessories joined together to enable gas to flow through them.

Market capitalisation: Company's stock value, calculated by multiplying the value of the company's shares in the stock market by its number of outstanding shares.

Gas centre: A centre at the disposal of the public regarding gas related services rendered by the company: Gas supply, sale of appliances and services, systematic inspections, etc.

Combined cycle, CGT: Power generation plants that use natural gas as a raw material. They are more efficient than other traditional thermal technologies, such as coal or fuel, as they produce energy in two phases. In the first phase, they generate electricity through direct gas combustion and, in the second, they take advantage of the residual gases, which are still hot, to generate water vapour that moves a turbine and in turn produces more energy.

Cogeneration, CHP:  Cogeneration enables us to produce and take advantage of heat and electricity in a combined manner. Cogeneration facilities are designed so that the vapour produced in a boiler can generate electricity and also be used to provide heat in industrial processes

Marketing companies: These are companies that buy electricity or natural gas (from producers or from other marketing companies) and sell it to their eligible customers or to other marketing companies under freely arranged conditions. Marketing companies use the facilities of transport and distribution companies to transport gas and electricity and supply it to their customers, for which they pay a charge.

Contracted consumption: This is the consumption agreed between the customer and the company, which is stated in the contract.

Consumption by third parties accessing the network: Consumption expressed in kWh for which the distributor invoices the marketing companies, corresponding to liberalised market customers, for third party access to the network.

Demand Charge Consumption: Consumption expressed in kWh that is billed for the various demand charges for electrical energy.

Estimated consumption: Consumption forecast for a customer; it is calculated every time a reading is taken, and according to the customer's seniority, the record of their readings and the estimation indicators they have activated. It is used as a validation screening mechanism to ensure that the consumption to be billed is correct.

Invoiced consumption: Consumption expressed in kWh that is billed according the gas volume or the electricity consumed during the billing period.

Meter: An instrument that allows us to calculate the amount of energy consumed in a determined period of time.

Smart meter: A technologically advanced meter that calculates electricity consumption in a more detailed manner than conventional meters. These devices provide the option of sending this information via a network to a service company control centre, which  may use the data for billing or monitoring purposes.

Universal Supply Point Code, CUPS: This is the code used for identifying supply points, for both gas and electricity. Codes for supply points consist of 20 and 22 digits for gas and electric respectively 22.

Market price: The price a stock or share holds on the stock market.


Environmental Impact Statement: This is the ruling of the appropriate environmental authority which determines whether or not it is advisable to go ahead and undertake the projected activity, and, if the ruling is positive, the conditions that must be met to protect the environment.

Tariff deficits: A tariff deficit is the difference between the total amount collected by network access tariffs (regulated tariffs set by administrative bodies and paid by consumers for their supply) and the actual costs associated with these tariffs (transport and distribution costs, premiums for certain technologies, etc.). Differences between regulated tariff collections and their actual corresponding costs are essentially generated for two reasons: deviations in the estimates and political or economic objectives of the successive governments, who, are ultimately responsible for establishing the regulated tariffs.

Electricity demand: Amount of electricity consumed by users in a determined period of time.

Distribution: Distribution is a regulated activity that is mainly aimed at transmitting energy or natural gas from transport networks to points of consumption. Distribution companies are responsible for distributing power, as well as constructing, maintaining and overseeing distribution installations. .

Dividend: A percentage of the company's profit that is distributed periodically among its shareholders.

Downstream (distribution and marketing): Those activities that take place from when hydrocarbons are received at the import terminals through to their distribution and marketing to the end user. Also see upstream (exploration and production) and midstream (processing and transport).


Energy efficiency: Set of programmes and strategies that reduce the amount of energy used by certain systems and devices without affecting the quality of the services provided. Efficiency protects the environment, ensures supply and sustainable practices for the use of resources.

Control and measurement station: A facility used to lower the pressure and measure the gas flow volume; they are the linkages between the gas pipeline network and the distribution networks.

Strategy, 20-20-20 objective: A European Union strategy for 2020 aimed at  reducing greenhouse gas emissions by 20% compared to 1990 figures, ensuring that 20% of  final energy consumption is sourced from renewable energies and achieving a 20% saving in future energy demands


Compressed natural gas: This is a fuel used in vehicles, due to it being economical and environmentally clean. It is considered a sustainable alternative for replacing liquid fuels. On occasion the terms "compressed natural gas" (CNG) and "natural gas for vehicles" (NGV) are used interchangeably. However, NGV, as well as CNG, can also be liquefied natural gas (LNG), which is also used as a fuel for vehicles, although to a much lesser extent.
Liquefied natural gas (LNG): Natural gas that has been liquefied by cooling to approximately -161°C at atmospheric pressure. Natural gas has a volume 600 times greater than liquefied natural gas (LNG).

Natural gas for vehicles, NGV: Natural gas used as fuel for vehicles.

Distributed generation: Distributed, or decentralised generation, in relation to electricity production at points of consumption. For this, smaller-scale facilities are used rather than conventional plants. The great advantage offered by this form of production is the reduced losses brought about by energy transportation and distribution. The most common forms of distributed generation in Spain are cogeneration and solar photovoltaic panels.

Renewable generation: Renewable energy is energy that is obtained from natural sources considered to be practically inexhaustible, some because of the vast amount of energy that they contain, and others because they are able to regenerate naturally.

Geothermal: Geothermal technology takes advantage of the earth's heat for electricity generation or for thermal uses (heating and cooling).

Gas pipelines: Pipelines that allow combustible gas to be transported, at high pressure and over long distances. They are made of high tensile carbon steel tubes, through which natural gas is transported. They can be buried or submerged in water, connected to international networks and can supply energy to one or several regions. When they run through a country, they are known as transit pipelines.


Thermal gap:section of electricity production that is supplied by thermal technologies: natural gas, coal and heavy fuel combined cycles.

Gas hub: Organised market for contracting gas, working in a similar way as the stock market


Power control switch, (PCS) An automatic switch installed by the  energy utility company when electricity is initially installed in homes that customers can use at any particular time to control the amount of power they consume. If their consumed power is greater than their contracted power, the switch automatically reacts by cutting the electricity supply off and it is necessary to rearm it to resume use
Electricity tax: The amount in euros corresponding to a tax levied on electricity bills. Chapter IX of Law 66/1997, of 30 December, the Tax, Administrative and Social Order Measures Act, levies the tax on electricity. The tax base for this tax is the result that comes from multiplying the total amount that, upon payment of the tax, would have been the tax base for Value Added Tax, excluding electricity tax itself, by a quotient of 1.05113, for an electricity supply in return for payment within the boundaries of the regions in which Value Added Tax between unrelated parties is applicable. The tax is levied at a rate of 4.864 %.

Coverage rate: The  coverage rate correlates the power available in the electricity system with peak demand. For Red Eléctrica de España (Spanish Power Transmission Company), the desired rate is 1.1. In other words, there is 10% more power available than the peak demand.

Infrastructure: Each one of the elements that, with its own characteristics and particular operating conditions, makes up the gas system and, by communicating between themselves, enable natural gas to be transported from points of entry (provisioning, supply) to points of exit (consumption, demand).


Kilowatt hour: An energy unit that is equivalent to the energy produced by one kilowatt (kW) of power for one hour, equal to 3.6 million joules. It is equivalent to 0.0949 cubic metres of gas.

Kilovolt:  Unit of electrical voltage equivalent to 1,000 volts.


Estimated reading: An estimated reading of the customer's consumption, obtained in the estimation process, and which is billed if a real or recently submitted reading is not available. This is also used in quarterly readings.

Real reading: A reading taken directly by the reading agent, without any third party intervention.

LED: The acronym LED stands for “Light-Emitting Diode”. A diode is a device manufactured with two different conducting materials that allow current to circulate in just one direction. When electricity passes through the diode, the atoms in one of the materials move with a higher level of energy. This energy is released when the atoms transfer electrons to the other material. Light is produced during this release of energy. They have many advantages when compared with incandescent light sources: their energy consumption is much less, they have a much longer duration, are smaller in size, and have good durability and dependability


Medium pressure:  In natural gas distribution activity, this corresponds to values between 0.05 and 4 effective (or relative) bar.

Forward market: Forward electricity or gas markets are a set of markets where, in the years, months, weeks or days prior to the physical delivery of energy, gas and electricity sales contracts with delivery periods greater than 24 hours are exchanged. The forward markets fulfil a crucial role in a developed liberalised market as they allow purchasers and sellers to manage their risks, while facilitating competition in wholesale and retail markets.

Daily market: The daily market is a market held the day before energy is delivered where purchasers and sellers exchange energy for each and every hour of the following day.

Intraday market: The intraday market is an adjustment market that takes place within the 24 hours prior to the time of generation / consumption. Participants can adjust their commercial position by buying and selling energy in the intraday markets

Liberalised market: This is the market in which the customer contracts their supply through any other marketing company that is duly authorised by the proper authority. The sales tariffs are agreed between the buyer and the sellers.

OTC market: The financial OTC (Over The Counter) market is an unorganised market in which the participants interchange, through intermediaries or brokers, financial settlement contracts drawn up in line with their preferences, without having to abide to the different participation and trading rules imposed by them.

Regulated market: This is the market in which the customer's gas and electricity is supplied by their authorised regular distributor. The sales rates for both energy types are set by law and published in the Official State Gazette (BOE).

Spot market: This is a market in which the delivery and payment of the negotiated good are made at the time of agreement. The price which is negotiated is known as the  spot price .

Cubic metre (CM): Unit for measuring gas volume. The amount of gas required to fill a volume of one cubic metre.

MIBEL: The Mercado Ibérico de la Electricidad (MIBEL) is the result of the integration between Spanish and Portuguese electricity markets.

Midstream (processing and transport): Activities which condition hydrocarbon production to meet the quality specifications required in the end markets, together with their transport from the processing facility to said markets. Also see upstream (exploration and production) and downstream (distribution and marketing).

Mini-hydraulic: A hydroelectric power plant is considered mini-hydraulic if it has an installed capacity of less than or equal to 10 MW.

Generation mix: Combination of power generation technologies that come together in one system.

MVA: MVA is an abbreviation of megavolt amperes, a power unit used frequently in large-scale  electricity generation facilities.

MW/MWh: Megawatts (MW) is a measurement that reflects the power, or capacity, of an electricity generation facility; equivalent to 1,000 kilowatts (kW). A combined cycle power plant, for example, typically has one or more groups of 400 MW. The largest plant in Spain has a power capacity of 1,400 MW, while a wind mill has around 1 MW. To measure the energy generated by a plant, or consumed by a customer, megawatts/hour (MWh) or kilowatts/hour (kWh) are used. kWh is the energy produced, or consumed, by a facility with an hourly capacity of 1 kW.


Odorisation: An operation that involves mixing odourless gasses with a product that has a smell so that they can be detected. For this, odorants are used, a chemical compound with a characteristic smell that is added to natural gas so that it can be detected.

OMIE: The organism in charge of overseeing the economic management of the daily and intraday markets for electricity production in the Iberian Peninsula. OMIE also organises various auctions for energy products related to electricity and natural gas.

OMIP: The Operador de Mercado Ibérico de la Energía (polo portugués), was established in  June 2003 and it focuses on the management of the MIBEL forward market in Portugal.


Capacity payment:  Market complementary remuneration mechanism that allows generation technologies to recover fixed costs, both in operations and in maintenance.

Liquefaction plant: A facility that manages to change the state of natural gas from gas to liquid.

Regasification plant: A facility that returns LNG to gas.

Charge (access tariffs): Utilisation cost of the different electrical and gas networks necessary to transport  to the final supply point (transport and distribution networks). This network access cost is fixed by these access tariffs colloquially known as charges.

Fuel cell: A fuel cell is an electrochemical device that allows the direct or continuous transformation of chemical energy resulting from the oxidation reaction.of a fuel into electricity. Fuel cells are similar to batteries, but they have a core difference; batteries store a fixed amount of energy between their electrodes, while fuel cells continue to work as long as they are fed with fuel and oxidants.

Pool: The name given to the electricity wholesale market by members of the energy sector. In this market, governed by the operator OMIE, electricity is bought and sold daily.

Power: In electrical appliances it is defined as the capacity of the appliances to produce work. It is also defined as the amount of work carried out in a unit of time. The measurement unit used is a Watt (W) or Kilowatt (kW).

Premium: In Spain, there is a supporting framework for renewable energies that establishes that each kWh generated by these technologies should receive a determined about of money or a premium, aside from that which is obtained through the sale of the kWh in the electricity market.

Matching process: This is the process through which the market operator deals with energy supply and demand, with the aim of achieving a price and a volume.

Supply points: Number of gas consumer-customers classified by the network owner companies to be connected, irrespective of their marketing company.

PVPC; Voluntary Price for the Small Consumer: This is the maximum price that Referral Marketers can charge consumers who are eligible for the price. This tariff was previously known as the Last Resort Tariff (TUR)  through which the price was set by the government.


REE: Red Eléctrica de España (Spanish Power Transmission Company) is the  Electric System Operator (SO). It guarantees continuity and safety in electricity supply, keeping our country's generation and consumption in constant balance, and it exercises these functions according to principals of transparency, objectivity and independence. REE is also the transport network managing body and acts as a single carrier.

Regasification: Regasification is the process which includes the whole series of stages found in the transportation of liquefied natural gas (LNG) to the natural gas distribution network. This process is carried out in a regasification plant, where natural gas enters as a liquid and comes out as a gas, being subsequently transported through gas pipelines to the thermal power plants and industrial and tourist centres. At present, there are six regasification plants in Spain: in Barcelona, Cartagena, Huelva, Sagunto, Mugardos and Bilbao. Enagás is also in the process of building a seventh regasification plant, El Musel, which is located in Gijón and will be brought into operation in 2011.

Special Regime: the  Special Regime for electricity production consists of the following technologies: waste treatmentbiomasshydraulics, wind energysolar and cogeneration.

Ordinary Regime: electricity generation activity may be considered under Ordinary Regime production whenever the necessary requirements for being considered under Special Regime production are not met.

Electricity distribution network: The electricity distribution network is made up of the lines, equipment yards, transformers and other electrical components with voltages below 220 kV, provided that they do not belong to the transport network. Likewise, the distribution network also includes all communication, protection and control assets, ancillary services, buildings and other ancillary elements, electrical or otherwise, that are necessary for the aforementioned specific facilities in the distribution network to operate properly.

Natural gas distribution network: The natural gas distribution network includes gas pipelines with a pressure equal to or greater than 16 bar as well as others which, regardless of their maximum designed pressure, provide gas to a single consumer using a gas pipeline belonging to the basic network or secondary transport.

Electricity transport network: The electricity transport network comprises the lines, equipment yards, transformers and other electrical components with voltages of 220 kV or above and all those other facilities, of whatever voltage, that are involved in international interconnection transport and, if applicable, the interconnections with Spanish electricity systems on the islands and off the Spanish mainland. Likewise, the transport network also includes all communication, protection and control assets, ancillary services, buildings and other ancillary elements, electrical or otherwise, that are necessary for the aforementioned specific facilities in the transport network to operate properly.

Natural gas distribution network:: The gas system includes facilities in the Basic Transport Network, the Secondary Transport Network, the Distribution Network and other additional facilities. The basic transport network comprises Liquefaction plants:Regasification plants, Primary Transport gas pipelines, underground storage facilities and international connections.

Network remonitoring: This is the set of tasks performed by qualified staff, provided with the relevant graphical information and suitable electronic material and implements, aimed at locating possible gas leaks existing in the pipes in the network.

Technical restriction: Any circumstance or incident arising from the situation of the transport network or system which, due to impacting on the supply’s security, quality and reliability conditions according to the rules and using the relevant operating procedures, requires programme modification using the system operator´s technical criteria.


Last Resort Supplier: Marketing company appointed by the government to assume the obligation of attending applications for natural gas supply from certain consumers, at a maximum price set by the Ministry of Industry, Tourism and Trade and previously agreed in the Government Executive Committee for Economic Affairs, which is termed the Last Resort Tariff.

System adjustment services: Actions that the generators provide to the SO in order to maintain the electrical system in physical equilibrium and within acceptable security levels in the immediate term: from a few minutes before dispatch to a few hours before.These services are managed in markets organized by the System Operator and fall into three categories: technical restrictions management, additional services management and diversion management.

Solar photovoltaic:  photovoltaic technology generates electricity in semiconductor devices integrated into the photovoltaic panels, which transform solar radiation energy into electrical energy..

Solar Thermal: Solar thermal energy consists of harnessing the sun´s energy to produce heat.

Switching: This is the process of transferring a customer whose energy supply is contracted on the regulated market, at the prices and tariffs published in the Official State Gazette (BOE), to the liberalised market, where the companies may offer discounts and additional benefits.


Voltage (high, medium, low): Electrical voltage is aphysical magnitude that quantifies the difference in electric potential between two points. It can also be defined as the workload per unitcharge exerted by theelectrical field on ancharged particle to move it between two determined points. This can be measured as a voltmeter.

Thermal Solar, Solar Thermal, Thermoelectric: A solar thermal power plant is an industrial facility where fluidis heated using solar radiation and used in a conventional thermodynamic cycle, producing enough power to move analternator to generate electrical energy as is done in a classic thermal power plant.

SAIDI: The duration of outage equivalent to the power capacity in medium voltage transformation facilities.

Securitisation: operation by which an entity transforms an asset or a collection right into standardised fixed income values, thus eligible for trading on securities markets.


Unesa: Spanish Association of Electrical Energy is a professional sectorial organisation for the coordination, representation, management, promotion and defence of associated electrical companies´ interests.

Upstream (exploration and production): Activities related to explorations and operation of hydrocarbon fields (gas and oil). Also see downstream (distribution and marketing) and midstream (processing and transport).


Watt: This is the basic unit for electricity, defined as one joule per second. The symbol for this is W. Expressed in units used in electricity, a watt is the power produced by a 1 volt difference in potential and an electrical current of 1 amp (1 VA). The power of electrical appliances is expressed in watts if they are low power; but if they are medium- or high-power appliances it is expressed in kilowatts (kW) which are equal to 1000 watts. One kW is equivalent to 1.35984 CV (horse power).

Volt: Unit of electrical pressure whose symbol is V.