The ACT government will lease a hybrid bus from Volvo and two electric buses from Carbridge as part of the $900,000 trial, measuring how the alternate energy buses perform against ACTION's existing diesel fleet.

The results will decide which technology will replace ACTION's ageing fleet, as the territory moves towards an emissions reductions target of 40 per cent below 1990 levels by 2020.

Transport currently makes up about one-quarter of the ACT's emissions, and transport minister Meegan Fitzharris said rolling out the buses would cement Canberra's position as a leader on climate change.

"This is a major part of our transition to more sustainable fuels in our public transport system," Ms Fitzharris said.

Carbridge chief executive Luke Todd said while electric buses were more expensive up front, they paid themselves off in about four years.

The company has six buses in operation at Sydney Airport, with another 11 on the way for Brisbane Airport, but Mr Todd said Canberra would be their first trial on public routes.

"We have plans to roll them out across the country," Mr Todd said.

The electric buses can drive for 600 kilometres per charge in a straight line or about 430 kilometres on route operations.

There are about 16,000 battery cells which can carry up to 324 megawatts of charge.

The electric buses will recharge overnight at the Tuggeranong depot, where special charging stations have been built at a "minor cost", Ms Fitzharris said.

Volvo's electric diesel hybrid requires no charging station and can work either as a diesel, electric or parallel hybrid bus.

"We see it as a stepping stone to the future. The future is electric, Volvo has electric chassis in development and actually in service in Europe which we are planning on bringing to Australia at some point in the future," Volvo Bus Australia's national contracts manager Ian Clarke said.

The price of diesel hybrid buses sits somewhere in the middle of standard diesel and electric buses, but use between 30 and 40 per cent less fuel than normal diesel engines.

ACTION's operational fleet technical officer Steven Jones said the buses regenerate when rolling, which has meant those driving them have had to be specially trained.

"The more you can roll and lightly brake, the more electricity you generate," Mr Jones said.

Public Transport Association of Canberra chair Damian Haas said it was a "sensible idea" to compare the two emerging technologies in the trial.

"I think hybrid and electric buses are the technology of the future. Diesel bus technology has peaked so I think a 12-month trial to see how they work in Canberra's fleet is a very good idea," Mr Haas said.

One more electric bus will join the trial in December, making a total of three alternate energy buses on Canberra's roads.

Mr Todd said when the ACT government placed the order for two electric buses, they only had one available so they had to build the second from scratch.

The electric bus trial was delayed after the ACT's government first contract fell through because the tenderer could not deliver the buses on time.