Acting Energy Minister Clive Brown said users with an annual average load of more than 34 kilowatts (300 megawatt hours per annum) - such as senior high schools, larger restaurants, mid-sized hotels, suburban shopping centres and medium-sized office blocks - would be the latest group able to choose their preferred supplier.

"Typically, these customers will pay between $45,000 and $206,000 a year for their electricity, so it is a large amount of expenditure," Mr Brown said.

"In the past, these customers have been obliged to buy their electricity from Western Power, but from today, any of these customers can opt to go to another electricity supplier if they feel they can get a better deal.

"These rules aim to create the environment to deliver customers competitive prices and better service."

The Minister said that in 1997 the previous government started phasing in access to Western Power customers by private electricity suppliers.

The first group of 'contestable' customers on the South-West grid were those with an annual average load of 10 megawatts (87,600 megawatt hours per annum) - the largest customers. The latest group brings the total of contestable customers to more than 2,300 - or 52 per cent of Western Power's power sales.

Mr Brown said the Gallop Government would extend the number of contestable customers to a total of 12,500 from January 1, 2005. This meant that any business with an annual average load of 5.7 kilowatts (50 megawatt hours per annum), such as a pizza shop or corner store, could opt for another electricity supplier.

In addition, Mr Brown said the Government's electricity reforms would open up the electricity market further by creating the conditions for private sector investment in power stations.