Ancillary services are all services necessary for the operation of a transmission or distribution system. They include compensation for energy losses, frequency control, voltage and power flow control (reactive power and active power), restoration of supply (black start, temporary island operation) and balancing. See Electricity Directive (2003/54/EC). Traditionally TSOs, big generators and big loads have been the actors involved with ancillary services, but the need for DSOs and DERs to participate is expected to increase due to increase in DG, RES and smart grid technologies.

Synonyms: Ancillary system services

Sources for further information:

In competitive electricity market the generation, trading and retail of electric energy are subject to competition, but (with rare exceptions) transmission, distribution and system operation are regulated monopolies. In competitive electricity markets there are market operators that provide market places or pools for trading electricity efficiently.

Sources for further information:Descriptions of instances of competitive electricity market can be found, for example, from www.nordpool.com, www.elmarknadshandboken.se and www.elexon.com

The organisation that is responsible for reading the data from the meter and passing it on for processing.

Demand response is the ability of electricity demand to respond to variations in electricity prices in 'market' or 'real' time. It can be achieved through load reductions or utilizing alternative onsite generation sources.

Synonyms: Demand side elasticity, Demand elasticity

Sources for further information:www.demandresponseresources.com

DER is a controllable energy resource connected to the electricity distribution network. Thus controllable loads, DG and electricity storage are DER.

Power generation connected to the electricity distribution network. Today DG is seldom centrally planned or dispatched, but that will change, because the increasing penetration of DG will make is necessary to increasingly use DG as controllable resources for the power system and for the electricity market.

Synonyms: distributed generation, embedded generation

Sources for further information:

• CIRED working group No 4 on Dispersed Generation, www.cired.be
• W. El-Khattam,  M.M.A.Salama,  Distributed generation technologies, definitions and benefits, Electric Power System Research 71 (2004), pp. 119-128.

DNO manages and operates a distribution network for energy (electricity, gas, heat) or water.  DNO has operators, control rooms and various ICT systems for distribution management and automation.  In the competitive electricity market the distribution of electricity is usually a natural monopoly controlled by the regulating authorities. 

Synonyms: Distribution System operator (DSO)

Final Customer is a customer of RESC.They are the users of the energy supplied and do not pass it on to further customers.

MAP is the organisation that owns the meters. This may be as part of a vertically integrated utility operation or it may be a separate function where the MAP leases the meters to the RESC or other party.

MO operates the billing meters. In some countries billing metering is unbundled and competitive and in some countries metering is part of the electricity distribution monopoly. Also in the latter case separate meter operators are common, because many distribution operators outsource the metering. In some countries (e.g. UK) the MO is split further to MAP (Meter asset provider) and MAM (meter asset manager)

Synonyms: MOP

the EU Directive 2001/77/EC[5] provides the following definition of renewable energy sources:  (2)(a) ‘renewable energy sources’ shall mean renewable non-fossil energy sources (wind, solar, geothermal, wave, tidal, hydropower, biomass, landfill gas, sewage treatment plant gas and biogases); further specifying biomass: (2)(b) ‘biomass’ shall mean the biodegradable fraction of products, waste and residues from agriculture (including vegetable and animal substances), forestry and related industries, as well as the biodegradable fraction of industrial and municipal waste;

Sources for further information:

- RENEWABLES IN GLOBAL ENERGY SUPPLY An IEA Fact Sheet, IEA-OECD Paris 2006

- DIRECTIVE 2001/77/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 27 September 2001 on the promotion of electricity produced from renewable energy sources in the internal electricity market.

An actor in the competitive electricity market that connects retail market customers with the bulk market.  

Synonyms: Retail Energy Supplier, Energy Retailer and often barely Supplier is used, when the context is strictly the electricity retail market.

Sources for further information:

Comments: See Supplier below

Two definitions with different meaning have been proposed:

1) Supplier is an actor in the electricity market that supplies energy to some other actor. (Also market pools are actors. ) Thus suppliers include the following: retail energy supply company, electricity generating company, electricity trader, etc.

2) Supplier is the licensed supplier of electricity to an end-user.
( Energy Broker = electricity trader, Generator = electricity generating company )

Sources for further information: Comment: These two definitions have different meaning and the latter definition is unclear. Resolve or avoid.

See Retail Energy Supply Company.

SO is the operator of the electricity transmission system. SO is responsible for balancing of the electricity transmission system, for example.

Sources for further information: Webpage of the European Transmission System Operators ETSO, www.etso-net.org

An actor who is responsible for the maintenance and operation of the High Voltage Electricity Transmission System.  This carries power from central power stations to the Distribution System, where responsibility transfers to the DSO.

Sources for further information: European Transmission System Operators ETSO www.etso-net.org