The big batteries will support the territory's own grid, providing power to help avoid blackouts during periods of high demand and when large fossil fuel generators fail in heatwave conditions.

The winners of the latest reverse auction round were Neoen of the Goyder South Wind Farm in South Australia, and GPG of the Berrybank Wind Farm in Victoria.

They will supply 200 megawatts of additional wind power into the grid.

In addition to the energy generation, successful bidders in the reverse auction were required to build a battery.

The locations of these batteries are yet to be determined.

Chief Minister Andrew Barr said the process delivered significantly lower prices than previous auctions, with an average price below $50 per megawatt.

ACT Climate Change Minister Shane Rattenbury said the auction would help Canberra maintain 100 per cent renewable electricity into the next decade.

"Our investment is on par with the Tesla Hornsdale battery on a per capita basis - the largest investment of its kind in the world," he said.

The two winning renewable energy companies will build large-scale batteries, located in Canberra.

As an indicator of their size, the Neoen battery - 50MW - has enough storage to power around 15,000 typical homes for an hour in the event of a blackout.

The GPG battery will be smaller at 10MW.

"We undertake these types of reverse auctions so that the ACT consumer can get best value electricity. This round has delivered the best pricing outcome to ACT households and businesses in the five rounds we've held," Mr Rattenbury said.

"Today's announcement means more investment in Canberra, more jobs, and more cutting edge research in renewables."

The price of wind power was about a third lower than in previous auctions.

Neoen have been granted a 10-year feed-in tariff at $44.97 per megawatt hour. GPG have been granted a 14-year feed-in tariff at $54.48 per megawatt hour.

The cost to households from all auctions is expected to remain below $4.90 per household per week.