It says Eskom has enough capacity to provide adequate electricity supply.
The country has been hit by load-shedding, which reached the highest levels this week.
President Cyril Ramaphosa blamed sabotage for Eskom's rolling blackouts.
NUM representatives who work at the Tutuka Power Station said the president was incorrectly informed.
They stated sabotage doesn't make sense, considering the lost capacity was estimated at 2,000 megawatts and each boiler produces 600 megawatts.
At least three boilers would have had to have been sabotaged in order to create the need for load-shedding.
Meanwhile, political analyst Dirk Koze said the sabotage claim is unfortunate.
"I think it's unfortunate that he refers to the notion of sabotage because it looks very much like he's using a conspiracy theory," Kotze said.