An Adelaide-based national solar-panel company, Unleash Solar, is going into voluntary administration.
Commissioner for Consumer Affairs Paul White said the company was being investigated for 17 complaints about faulty equipment and warranty work not being completed.
Mr White said it had not been dealing satisfactorily with customers' issues.
"What the company has told us is that it will take between three and six months to source replacement inverters from China," he said.
"We believe that's not reasonable and those goods are unfit for purpose and it needs to be rectified sooner than that.
"We're advising the public to be wary of dealing with this company, Unleash Solar."
Unleash Solar had been a sponsor of A-League team Adelaide United and SANFL club Woodville West Torrens.
The Adelaide 36ers basketball team recently dropped the company as a sponsor and is in negotiations to recover money allegedly owed.
Woodville West Torrens CEO Uby Faddoul said Unleash Solar had been its oval sponsor for two years, but negotiations on a further agreement broke down recently.
Unleash Solar could not be reached for comment.