Eskom said on Monday that the test, which will take place between 10am and midday on Tuesday, will affect Atlantis, Bloubergstrand, Van Riebeekstrand, Sunningdale, Duynefontein, West Beach, Melbosstrand, Parklands, Philadelphia and Robben Island.
"The siren system has been installed in your area to inform you of an emergency at Koeberg," Eskom said in a statement to residents. "The sirens are for the benefit of the public and need to be maintained and in a working condition at all times."
It said Tuesday's planned siren test forms part of Koeberg's emergency plan in the event of a nuclear accident.
"You will be alerted to the testing of the sirens by public address announcements before and after the sirens are sounded. Don't take any action," Eskom warned.
"If necessary, individual sirens may be retested on 5 and 6 March for maintenance purposes- As a precaution, please ensure that your pets are indoors or are in an area where they cannot escape. Due to the volume and the sound of the wailing test done, dogs have been known to run away from their homes."