Both units of the Koeberg nuclear power station in the Cape Peninsula are now out of commission, SABC news reported on Friday.

Unit one was shut down following a detection of a suspected fault in the cooling system.

Eskom's spokesperson Tony Stott said this would mean a loss of another 900 megawatts from the grid.

On Monday, unit two shut down as a result of a technical fault and would be out of action for three weeks.

Stott said Eskom did not foresee any immediate power cut as demand was usually low over weekends.

He said engineers were investigating the full nature of the problem, the SABC reported.

Specialists from Alstom — the original equipment manufacturer — are at the site to assist with the inspection and diagnosis of the problem which resulted in the closure of station's second unit.

Eskom appealed to consumers to reduce electricity demand by switching off all non-essential lights and electrical applications during peak hours, 5pm until 9pm.

Sapa