The South Australian Chamber of Mines and Energy and 27 other South Australian businesses have been given the green light to establish a joint electricity purchasing group, for the next 11 years.
This means the group will be able to buy electricity at better prices.
Together, the group's total load of 269 MW accounts for around 16 per cent of electricity demand in South Australia, and less than one per cent of the National Electricity Market, according to the ACCC.
"Three more companies have joined the buying group since the ACCC made its draft determination in April, increasing the total load from 245MW to 269MW. This strengthens the benefits of the conduct," ACCC Chairman Rod Sims said.
"The greater combined load increases the group's bargaining power in the retail supply of energy contracts in South Australia, which will be good for competition in a market which is highly concentrated at times on the supply side."
Sims said the joint tender has the potential to change wholesale market dynamics, by allowing generators to use existing plants more efficiently - or encouraging new entrants into South Australian electricity generation.
"This could bring the benefits of increased competition in the wholesale market for electricity," Mr Sims said.
The ACCC also considered the transaction cost savings likely to result from the tender provided a further source of public benefit.
In the 2017-18 Federal Government, the government is making $110 million of its $1.6 billion of spending available to kickstart private investment in a solar thermal plant in Port Augusta in South Australia.