The Wellington North project in New South Wales and smaller Wunghnu project in Victoria, would give it five projects operating or under construction, with a combined capacity of more than 1 gigawatt (GW), Lightsource bp said.
That would make the company Australia's biggest solar developer by capacity, it said.
Australia's new Labor government is looking to slash carbon emissions by 43% from 2005 levels and have 82% of power generated by renewable energy by 2030.
"We see the acceleration of renewables happening more rapidly than previously anticipated," said Adam Pegg, Lightsource bp Australia and New Zealand managing director, in a statement.
Australia is expected to make a "significant contribution" to the company's global target of 25 GW of solar power by 2025, Pegg said.
"The outlook for solar in Australia and the region is incredibly strong, with increasing political support, greater investor certainty, and capital looking to participate in the sector," he said.
To help underpin the new solar projects, Lightsource bp has signed power purchase agreements with Engie SA, Orica Ltd and Mars Australia.
Orica, the world's biggest maker of industrial explosives, said with the Wellington North solar deal, renewables will make up around 30% of its global electricity supply, half way to its 2030 target of sourcing 60% of its electricity from renewables.
($1 = 1.4259 Australian dollars)
(Reporting by Sonali Paul; Editing by Tom Hogue)
By Sonali Paul