The fourth unit of Eskom's Kusile power station is up and running and expected to soon contribute an additional 800MW to the country's power system.

Eskom said on Thursday that unit 4 was connected to the national grid for the first time on December 23.

“The unit will supply electricity intermittently during the testing and optimisation phase over the next six months, before being handed over to the generation division to officially be part of the commercial fleet,” it said.

“This will further assist Eskom as it works to address the supply capacity challenges.”

Eskom described the feat as a milestone towards what the country needs to power SA and its economy.

“This achievement signifies the efforts from the team in ensuring that the power station project is completed without any further delays, which would help strengthen SA’s electricity capacity,” said Bheki Nxumalo, group executive for group capital.

Construction and commissioning activities on the remaining Kusile units 5 and 6 continue.

“At completion, the station will consist of six units, and will produce a maximum 4,800MW.”

Situated near Emalahleni in Mpumalanga, Kusile is SA's largest construction project and will be the world’s fourth-largest coal plant once completed.

Kusile will also be the first power station in SA and Africa to use wet flue gas desulphurisation (WFGD) technology, a state-of-the-art way to remove oxides of sulphur (SOx), for example sulphur dioxide (SO2), from the emissions of power plants that burn coal or oil.