The big three electricity retailers are charging as much as triple the rate for power in deregulated markets compared with the ACT, costing consumers hundreds of dollars a year, according to a study by energy economist Bruce Mountain.

The report, commissioned by the GetUp! group, analysed how much AGL, EnergyAustralia and Origin Energy were charging customers for the retail component of bills. It found South Australian customers, for instance, were paying about twice as much for the retailing component as it cost to generate the electricity itself.

Taking a snapshot of offers on the market, Mr Mountain found NSW households would typically cop an annual retail charge of about $444, $485 in Victoria and about $650 in SA. By contrast, ACT household could expect to pay about $225 in their regulated market.

"Once deregulation occurs, prices rise substantially," Mr Mountain said, adding NSW prices from the big retailers had jumped 10-15 per cent since caps were lifted in July 2015.