Synergy has come under fire for a second time this year after admitting to taking $40 million from Western Australia customers.

The state-owned utility is blaming a “system failure” for the error as they work to pay back hundreds of thousands of people.

“This isn’t good enough, it’s not acceptable and we’ve let our customers down,” Synergy chief executive Kurt Baker said.

The provider collected overpayments from accounts that were meant to be closed, impacting 174,000 customers – both residential and business.

The payments date back to 2009 for amounts ranging from $1 to tens of thousands of dollars.

“Our systems and our processes should identify that, but they haven’t, so our systems have let us down,” Baker said.

He reassures customers they’ve now been stopped but wouldn’t reveal exactly when Synergy discovered the blunder.

“We’ve only concluded that in recent times,” he said.

It’s expected to take several months for customers to be reimbursed but Synergy’s CEO said the company had hired extra staff to speed up the process.

“It’s utterly unacceptable that this situation occurred, and those who have overpaid deserve reimbursement immediately,” declared Reece Whitby, the state minister.

It isn’t the first time Synergy has slipped up.

In March, it was discovered that nearly 3000 vulnerable customers using Centrepay experienced overcharges on closed accounts, with automatic deductions amounting to a total of $2.29 million.

“This is a matter of trust. The people of Western Australia must be confident that their government departments are acting in their best interest, and in this instance, that trust has been compromised,” stated opposition energy minister Steve Thomas.