Canberrans will save an average $24 a year on electricity bills in the year from July, after the Australian Energy Regulator rejected a bid by ActewAGL for higher prices.

Small businesses' bills will fall by an estimated $35 on average.

But the saving looks to be offset by a separate price increase being considered by the second body that regulates electricity prices in the territory - the Independent Competition and Regulatory Commission. The commission is considering an average increase of $23 in retail electricity costs.

For its distribution arm, ActewAGL had asked for a price rise that would have added an estimated $45 to domestic bills and $68 to small businesses, but the bid has been knocked back by the energy regulator.

The regulator says ActewAGL can collect $173 million in distribution and transmission charges from customers in the year, about 7 per cent less than it requested.

The regulator also knocked back price rises requested by NSW electricity distributors Ausgrid, Endeavour and Essential, saying it had not accepted the companies' proposed rates of return and had a set a lower allowance for corporate tax.

The regulator noted that ActewAGL overspent its capital expenditure allowance by more than 10 per cent in every year since 2010, and in 2013-14 it overspent by $63 million - spending $384 million on capital works instead of the allowed $321 million.

It has forecast $400 million of capital expenditure for the five years from 2014, which is $79 million (25 per cent) more than the allowed capital spending for the past five years, and $16 million more than actual spending for the past five years.

Asked about the impact of the pricing decision on ActewAGL's business, chief executive Michael Costello said he would need to assess the decision in detail over the next few days.

Electricity prices are set by two bodies - the Australian Energy Regulator, which sets prices for electricity distributors (owners of the poles and wires), and the Independent Competition and Regulatory Commission, which sets retail prices.

Because ActewAGL is both a distributor and retailer, its prices are set by both. The retail price decision is due on June 6.