Power utility Eskom on Wednesday called on consumers to switch off geysers, pool pumps and all non-e.
Of the 13, Trevor Noah, DJ Sbu and Bonang Matheba are the only South Africans who made the list.
Other celebrities to make the list are Serge Ibaka, a Congolese basketball player who plays in the American National Basketball Association, Julius Onah, a Nigerian filmmaker, and Ajak Deng, a model from Sudan.
"I'm so honoured to have made the Forbes list. It was amazing," Matheba said. "I never thought I'd ever make it to a Forbes list and being the only South African female to have made the list and to be among greats like Trevor Noah and DJ Sbu is an honour.
"Making the Forbes list contributes to a great start to the new year. Who knows what else is in store for the rest of the year?"
Matheba said she thought her work ethic and consistency had helped her earn a coveted spot on the list.
"There is also the fact that I am able to bounce back from hardships and tend to kick butt, so no one can tell me anything about attitude," she said.
Noah made waves in the Unites States last year when he made appearances on the Tonight Show with Jay Leno, the first South African comedian to do so.
DJ Sbu, real name Sibusiso Leope, has helped launch the music careers of artists such as Zahara and the late Brown Dash through the TS Records label.
Ahmen Soultan, Recording Artist, Morocco
David Oyelowo, Actor, Nigeria
Trevor Noah, Comedian, South Africa
Serge Ibaka, NBA basketball player, Republic of Congo
Julius Onah, Film-maker, Nigeria
Kudzanai Chiurai, Artist, Painter, Zimbabwe
Mataano, Fashion Designers, Ethiopia
DJ Sbu, DJ, Recording Artist, Social Entrepreneur, South Africa
Ajak Deng, Supermodel, Sudan
Camp Mulla, Hip Hop Group, Kenya
Sarkodie / R2Bees, Recording Artists, Ghana
Mark Tonderai Hodges, Film-maker, Zimbabwe
Bonang Matheba, Media Personality, South Africa