The consumer watchdog is “painstakingly” sifting through data to ensure households are paying less for their electricity after the repeal of the carbon tax.

The latest consumer price index showed electricity prices fell 5.1 per cent in the September quarter, the biggest quarterly drop since records began in 1980.

Australian Competition and Consumer Commission chairman Rod Sims told a Senate committee hearing in Canberra on Friday there could be further price falls.

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“What we’re going to do in a very painstaking way is to check that all the reductions come through,” he said.

The commission needs to understand what other factors caused price changes when the carbon tax no longer applied.

In August notices were issued to 250 energy companies to estimate to their customers how much the removal of the carbon tax would affect prices.

The ACCC has 30 staff checking the data.

Mr Sims said the commission is not seeing a lot of consumer complaints so far.

However, the commission is investigating claims by Qantas and Virgin that while they had a carbon surcharge when the tax came in, they didn’t pass that on to customers.

The airlines argued there was nothing to remove now that the impost had been abolished.

“We are looking closely at that,” Mr Sims said.