State-owned electricity utility Eskom says its Medupi coal-fired power station in Limpopo has produced first power out of its last unit.

In a statement late on Tuesday, Eskom said Unit 1 attained 190MW earlier in the day, making it the last of Medupi's six units to be synchronised to the national grid.

First synchronisation or first power is when the generator in the unit is electrically connected to the national power grid so that it is aligned with all other generators.

Unit 1 will start generating and delivering electricity intermittently into the grid over several months during a testing and optimisation phase to ensure the country has stable supply.

Eskom was forced to implement rotational powercuts earlier this year to avoid a total collapse of the grid as supply struggled to keep up with demand.

"The first synchronisation of Unit 1 also marks a key milestone towards the full commercial operation of the unit ahead of its scheduled commercial operation in November 2020," the company said on Tuesday.

"The swiftness in delivering the unit has been due to the fact that lessons learned on previous units were implemented."

The testing and optimisation of the unit will result in it being able to generate full power of 800MW, taking it a step closer to being commercially operational, which generally occurs within six to nine months after first synchronisation.

"Eskom takes pride in Team Medupi and its contractors having achieved this milestone. The team is commended for the dedication and commitment for working tirelessly to ensure the synchronisation of Unit 1," Eskom utility said.