Some South Australian energy companies could have done a better job in their changes to billing systems, with the shifts blamed for a massive increase in complaints this year.

Almost fifty per cent more angry customers contacted South Australia’s energy and water Ombudsmen in the last 12 months than in the preceding year.

The Ombudsman's annual report says over 21,000 complaints were lodged; the majority were over late, missing or inaccurate bills.

Ombudsman Sandy Canale said part of the increase could have been because two providers, Origin Energy and Energy Australia, changed their billing systems in that period of time.

“There were a number of instances of late bills, no bills or in some cases inaccurate bills which caused consumers to question what was happening and it required our intervention to resolve the problems,” he said.

Mr Canale says energy companies need to work harder to provide more than just utilities for their customers.

“To be prepared for the questions that are going to arise when customers get bills which may be delayed over two or three periods and then be able to reassure the customer that action will be taken to resolve the complaint in a prompt fashion.”

The Energy & Water Ombudsmen found complaints were down for some suppliers.

Reports say Origin Energy has declined to comment, and a spokesperson from Energy Australia confirmed a new billing system had caused problems for some customers, also apologising for interruptions.