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In economic terms, electricity (both power and energy) is a commodity capable of being bought, sold, and traded. An electricity market is a system enabling purchases, through bids to buy; sales, through offers to sell; and short-term trades, generally in the form of financial or obligation swaps. Bids and offers use supply and demand principles to set the price. Long-term trades are contracts similar to power purchase agreements and generally considered private bi-lateral transactions between counterparties. Wholesale transactions (bids and offers) in electricity are typically cleared and settled by the market operator or a special-purpose independent entity charged exclusively with that function. Market operators do not clear trades but often require knowledge of the trade in order to maintain generation and load balance. The commodities within an electric market generally consist of two types: power and energy. Power is the metered net electrical transfer rate at any given moment and is measured in megawatts (MW). Energy is electricity that flows through a metered point for a given period and is measured in megawatt hours (MWh). Markets for energy-related commodities trade net generation output for a number of intervals usually in increments of 5, 15 and 60 minutes. Markets for power-related commodities required and managed by (and paid for by) market operators to ensure reliability, are considered ancillary services and include such names as spinning reserve, non-spinning reserve, operating reserves, responsive reserve, regulation up, regulation down, and installed capacity. In addition, for most major operators, there are markets for transmission congestion and electricity derivatives such as electricity futures and options, which are actively traded. These markets developed as a result of the restructuring of electric power systems around the world. This process has often gone on in parallel with the restructuring of natural gas markets. ==History== One early introduction of energy market concepts and privatization to electric power systems took place in Chile in the early 1980s, in parallel with other market-oriented reforms associated with the Chicago Boys. The Chilean model was generally perceived as successful in bringing rationality and transparency to power pricing. Argentina improved on the Chilean model by imposing strict limits on market concentration and by improving the structure of payments to units held in reserve to assure system reliability. One of the principal purposes of the introduction of market concepts in Argentina was to privatize existing generation assets (which had fallen into disrepair under the government-owned monopoly, resulting in frequent service interruptions) and to attract capital needed for rehabilitation of those assets and for system expansion. The World Bank was active in introducing a variety of hybrid markets in other Latin American nations, including Peru, Brazil, and Colombia, during the 1990s, with limited success. A key event for electricity markets occurred in 1990 when the UK government under Margaret Thatcher privatised the UK electricity supply industry. The process followed by the British was then used as a model or at least a catalyst for the deregulation of several other Commonwealth countries, notably Australia and New Zealand, and regional markets such as Alberta. However, in many of these other instances the market deregulation occurred without the widespread privatisation that characterised the UK example. In the USA the traditional model of the vertically integrated electric utility with a transmission system designed to serve its own customers worked extremely well for decades. As dependence on a reliable supply of electricity grew and electricity was transported over increasingly greater distances, power pools were formed and interconnections developed. Transactions were relatively few and generally planned well in advance. However, in the last decade of the 20th century, some US policy makers and academics projected that the electrical power industry would ultimately experience deregulation and independent system operators (ISOs) and regional transmission organizations (RTOs) were established. They were conceived as the way to handle the vastly increased number of transactions that take place in a competitive environment. About a dozen states decided to deregulate but some pulled back following the California electricity crisis of 2000 and 2001. In different deregulation processes the institutions and market designs were often very different but many of the underlying concepts were the same. These are: separate the potentially competitive functions of generation and retail from the natural monopoly functions of transmission and distribution; and establish a wholesale electricity market and a retail electricity market. The role of the wholesale market is to allow trading between generators, retailers and other financial intermediaries both for short-term delivery of electricity (see spot price) and for future delivery periods (see forward price). Some states exempt non investor-owned utilities from some aspects of deregulation such as customer choice of supplier. For example, some of the New England states exempt municipal lighting plants from several aspects of deregulation and these municipal utilities do not have to allow customers to purchase from competitive suppliers. Municipal utilities in these states can also opt to function as vertically-integrated utilities and operate generation assets both inside and outside of their service area to supply their utility customers as well as sell output to the market. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Electricity market」の詳細全文を読む スポンサード リンク
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