SA Power Networks has been hit with a $40,000 fine after human errors left customers on life support machines without electricity during planned power outages.

The network provider must give customers at least four workdays' notice of any planned outages but on two occasions in December 2015 and February this year it failed to do so.

The Australian Energy Regulator fined SA Power Networks $20,000 for each error.

SA Power Networks spokesman Paul Roberts said the outages had been investigated.

"While neither of these incidents caused any harm for the customers concerned, we recognise they would have been challenging and apologise to the customers involved for our failure to notify them," he said in a statement.

"Both [incidents] related to human error. In response, additional training has been provided for relevant staff," Mr Roberts said.

He said improvements had been made to the process of notifying people of planned power outages.

Also, customers on life support will be visited or contacted by phone before any disruptions under the new measures.

Australian Energy Regulator chairwoman Paula Conboy said protecting customers requiring life support equipment was a priority.

"An unexpected loss of supply can have serious, and potentially fatal, consequences for customers who depend upon life support equipment," she said.