A public-owned energy retailer would drive electricity prices down and stop big companies rorting, the Greens say.

Greens leader Richard Di Natale wants to introduce a national energy retailer, PowerAustralia, to focus on the public interest, rather than maximise profits.

He will announce plans for the retailer in a speech to the National Press Club in Canberra on Wednesday.

"For-profit energy retailers have not improved the quality of our lives by spending our money mercilessly advertising back to us," Senator Di Natale says.

"They have simply captured profits instead of creating value."

The Greens' plan would see PowerAustralia deliver energy at the lowest cost, after the Australian Consumer and Competition Commission found the average residential customer pays $273 a year in a retail costs and profit.

"By eliminating profits completely, and taking away the excessive spending on advertising, this non-profit public retailer would save an average family around $200 a year," Senator Di Natale says.

"This public retailer would provide the competition needed to end price gouging and super profits, while pushing down prices.

"It would also contract the next wave of renewable energy projects that the public so desperately wants to see built."

Senator Di Natale said the retailer would create real choice and return a dividend to the national budget that can be reinvested.

He said a majority of Australians blame excessive profit margins and privatisation of generation and supply for the spike in electricity prices.

"The time has come for publicly-owned institutions to play a much bigger role in the provision of essential services," he says.

The plan comes on the bank of the Greens' push for a People's Bank, which would offer fair financial services and help more first homebuyers.