The purchase and sale relations in the energy market are framed in one of the following environments:

• Ambiente de Contratação Regulada (ACR) [Regulated Contracting Environment] - the contracting is formalized in energy auctions made possible by the CCEE. The contracts are bilateral, regulated by ANEEL and celebrated between sellers (traders, generators, independent producers or self-producers) and buyers (distributors).
• Ambiente de Contratação Livre (ACL) [Free Contracting Environment] - it covers bilateral contracts also regulated by ANEEL, but with free negotiation among the generating agents, traders, free consumers, importers and exporters.

The agency responsible for managing the market is the Câmara de Comercialização de Energia Elétrica (CCEE) [Chamber of Commercialization of Electric Energy], regulated by Decree number 5.177, of August 12, 2004, succeeding to the Mercado Atacadista de Energia (MAE) as the Civil Association integrated by the agents of generation, distribution and commercialization. The institution perform a strategic role to make viable the purchase and sale operations of electric energy, registering and administering contracts signed among generators, traders, distributors and free consumers.

CCEE registers the aggregation of net volumes of energy measured, generated and/or consumed. The differences are liquidated in the Short-Term Market and integrated to the calculation of the PLD (Preço de Liquidação das Diferenças) [Liquidation Price of the Differences]. The PLD is formulated weekly and is differentiated for each submarket (North, Northeast, South and Southeast / Center-West) and for each level of load (light, medium or heavy).

The value of the PLD is based on the Custo Marginal de Operação (CMO), [Marginal Cost of Operation] informed by the Operador Nacional do Sistema (ONS) [National System Operator], taking into account estimated availability information and demand for the following week, within a maximum and minimum price limit established annually by Aneel and always aiming at optimizing the operation of the Sistema Interligado Nacional.

The market agents, the commercializing companies exercise, preponderantly, the following functions:

• Promote the rationalization in the apportionment of the balance and deficits of energy through the incorporation of the laws of supply and demand.
• Assume the price risk and make the balance price viable.
• Assume amount and deadline risks, adjusting the purchase and sale portfolio.
• Offer liquidity to the market.
• Increase the liquidity of the free market and of the market of difference liquidation.