The agreement gives Alinta access rights to the South West Interconnected System (SWIS) and pledges back-up support from Western power during times of shutdown.

To gain access to the network, new generators entering the market must have standby arrangements in place to supply their customers with power while their generator is out of service for routine or breakdown maintenance.

Alinta intends to construct a 140MW co-generation facility at the Alcoa Pinjarra alumina refinery and the agreement sees Western Power providing standby power to cover any unavailability of the 140MW generator.

The agreement was signed after eight months of negotiations and is anticipated it will come into effect when Alinta's gas-fired Pinjarra plant comes online in the second half of 2005.

The arrangement will stand until the introduction of the new electricity market in 2006.

Ongoing deregulation of the electricity market means that since 1 January 2003 consumers using more than 34kW of electricity have been able to choose their electricity retailer.

With the proposed 140MW generating unit, Alinta will be able to supply about 1,000 gigawatt hours (GWh) or almost 10% of Western Power's current customer sales.