The Eskom board has confirmed that Brian Molefe has reported for work on Monday morning as the utility's CEO.
A small group of protesters wanted to prevent him from entering Megawatt Park but demonstrated instead, saying he must leave.
Brian Molefe has been at work for several hours already.
Protesters planned to stop him from entering Eskom's Megawatt Park but arrived well after Molefe had reported for duty.
Molefe has already held what the board says is a successful meeting.
Meanwhile, the DA has lodged papers at the high court in Pretoria to interdict Molefe's reappointment.
The Eskom board announced on Friday that Molefe has been reinstated to his position as CEO following a dispute about his R30 million pension payout.
Molefe resigned last year after the Public Protector's State of Capture report revealed his alleged relationship with the controversial Gupta family.
There's been widespread condemnation of the board's decision to offer Molefe his job back, especially after he left the utility under a cloud after his relationship with the Guptas was made public.
With the African National Congress (ANC) joining organised business, labour unions and other parts of society in condemning this move, it appears this could be a test of strength between Luthuli House, the Eskom board and possibly President Jacob Zuma.
The ANC has demanded a meeting with Minister Brown and said it will order her to reverse this decision.
But Brown may feel she was appointed by Zuma and could be caught in the middle.
At the same time, Zuma's opponents in the party may feel that incidents like this mean they have to act now and can't wait until the party's December conference.