The North West Interconnected System (NWIS), Regional Power (RP) and the South West Interconnected System (SWIS) are the three main geographical areas which make up the Western Australian electricity market.

The South West interconnected System (SWIS) is the primary electricity grid in Western Australia, supplying the bulk of the South-West region. It extends from Albany in the South, to Kalgoorlie in the East and up to Kalbarri in the North.

The SWIS is geographically isolated from the interconnected power systems of Eastern and Southern Australia and with these networks being separated by a distance of some 1,500 kilometres; it is unlikely that the SWIS will be connected to the National Electricity Market (NEM) in the future.

With a peak demand of around 3,800MW, primarily during the summer period, and a total installed generation capacity of just over 4,500MW, the SWIS is a much smaller power system compared to overseas international markets. Around 65% of the installed generation capacity is owned by the State Government generator, Verve Energy, and the remaining 35% is privately owned. In total, the network supplies around 840,000 retail customers, which is comprised of industrial and commercial users.

Energy production within the SWIS derives predominately from non-renewable fuels such as black coal, natural gas and oil. Renewable energy sources, largely wind, hydro and biomass, only account for 1% of peak demand and this number is set to increase in 2010 with the Western Australian State Government targeting 6% of electricity to be sourced from renewable energy.