An ActewAGL spokesman said as a result of the Gillard government's carbon price being repealed in July, electricity prices in the ACT would drop by about two cents per kilowatt and gas prices would fall by approximately $2 per gigajoule.

Overall, he said average Canberra utility prices were estimated to drop $222 a year for electricity users and $98 a year for those connected to natural gas, about $320 annually in total.

He said the prices would come into effect for all electricity bills from August 1, 2014 and be backdated to the beginning of July, meaning customers will no longer pay the carbon price from July 1.

"Customers who have already paid their bill will receive a credit for the carbon amount which will appear in their next bill," the spokesman said.

"Customers who receive their bills after August 1 2014 will only see the carbon exclusive prices on their bills,"

Gas prices in the ACT will change from September 2014 and also be backdated to July.

The ActewAGL data suggeststhe drop in electricity and gas prices has been larger for Canberrans than was originally predicted by the Abbott government before the carbon price repeal.

Treasury modelling earlier in 2014 said the average household's annual electricity bill would drop by about $172 following the repeal, with gas bills falling by $53.

For residents living across the border in NSW, ActewAGL said it was still working through the changes and would have more information for users shortly.

But the spokesman said all changes would be backdated to July 1, 2014.