Energy Minister Geoff Wilson on Wednesday announced a new billing code that will force power companies that overcharge to give a $40 credit to affected customers on their next bill.
It follows a series of glitches where pensioners missed out on the government's rebate of $165 a year and were wrongly charged the state's ambulance levy.
The bungles cost Origin Energy $50,000, AGL $30,000 and Queensland Energy $15,000 in fines.
Wilson said the $40 penalty would hit power companies in the hip pocket and pressure them to life their game.
"I've had a gutful of power billing companies doing the wrong thing by their customers," he said.
But Opposition Leader Lawrence Springborg said it was proof that companies were doing as they wished in the deregulated energy sector.
Springborg said it should not be the responsibility of householders to police energy retailers.
"You've got the poor old pensioners of Queensland who have now got to be the police officers as well," he told reporters.
"They've got to go out there and try to dig up the fact they have been overcharged, they've got to pursue it.
"The government has basically admitted that as it's gone to retail contestability, they've taken their eye off the ball."
Springborg said the $40 penalty was not a great deterrent.
"Forty dollars is hardly going to have them shaking in their boots," he said.
One of the retailers previously fined, AGL Energy, responded positively to the move.
A spokesman said the company sent millions of bills each year, and made every effort to avoid mistakes.
"AGL would like its customers, and all other Queensland consumers, to understand that it is not deliberately making mistakes, especially in regard to pensioners' bills," the spokesman said.
"Every effort is made to ensure that our customers are not out of pocket.
"A small number of billing errors have occurred in the past and we fixed them as soon as we were made aware of them.
"We have put systems in place to help prevent such errors happening again."
Energy Ombudsman Barry Adams welcomed the penalty, saying 96 cases concerning fees and charges were investigated in August alone.
"For too long, energy companies are not giving Queensland's pensioners the rebates they are entitled to," Adams said.
The new code will not penalise companies that adjust an overcharged bill before it has been paid, or if the billing error relates to a faulty meter or other causes outside their control.
It is expected to start in a matter of weeks, and will be administered by the independent Queensland Competition Authority.
