Close to 500 maintenance workers will be bound by strict COVID-19 safety protocols as they commence work on a major maintenance project at Eraring power station on Thursday.
The project, which has been delayed for a year due to the pandemic, will see Unit 4 taken offline.
The work is due to run until October 21.
It will involve conducting inspections and repairs to boilers, turbine and cooling water systems in Unit 4.
The project will ensure Australia's largest coal-fired power station, which currently meets a quarter of the state's power needs, is able to run at full capacity for the summer peak period.
Origin Energy declined to put a dollar figure on the project.
A spokesman said the company had been working with experts for several months to develop COVID-19 management plans and controls for the outage.
"We have put in place a significant number of controls, including PCR (polymerase chain reaction) and Rapid Antigen tests for personnel attending site, to ensure the safety of our staff, contractors and the community during the Unit 4 maintenance outage," he said.
"These works were deferred last year and are now necessary to ensure the safe and reliable operation of Eraring during the upcoming summer peak consumption period."
Origin Energy announced earlier this year that it will permanently switch off Eraring's first generator in 2030.
The 2800 megawatt power station is due to cease production in 2032. Unit 4 will close in 2030, and Unit 1 in 2031. The other two units will shut, as intended, in 2032.
However, those dates could be brought forward depending on developments in the rapid transition to renewable energy.
Origin unveiled plans in January to develop Australia's largest battery at Eraring as part of a plan to take pressure off the energy network and provide back-up for renewable energy generation.
The 700 megawatt battery will be able to send power into the grid for up to four hours at times when renewable sources are not available.
The project will be developed in three phases. The first phase is expected to be operational by late 2022.
The company has issued an expression of interest for the supply and installation of the battery.
A connection enquiry has also been lodged with TransGrid to connect the battery to the national grid via the Eraring substation.
Origin executive general manager, energy supply and operations, Greg Jarvis, said the project was consistent with the company's decarbonisation goals and recent NSW government energy policy announcements.
"We recognise we have an important role to play in positioning Origin's electricity generation portfolio to support Australia's rapid transition to renewables," he said.
"The deployment of this battery at Eraring will support Origin's orderly transition away from coal-fired generation by 2032, while complementing the policy objectives of the NSW energy roadmap."
