The slower-than-planned arrival of electric buses to Transport Canberra's fleet prompted the government to trim its target for the zero-emission vehicles entering service.
The target was cut from 60 zero emission buses in service by 2024-25 to 56 between the 2023-24 and 2024-25 territory budgets.
The budget papers this year said the "revised" target, included as a performance indicator for Transport Canberra, was a result of "lead times for construction of additional electrical supply infrastructure".
Transport Minister Chris Steel told budget estimates on Monday the government was regularly reporting against the ultimate target to have a 100 per cent zero-emissions bus fleet by 2040.
"The overarching target is transitioned by 2040 or earlier, and there are some interim targets between. But the fundamental target that we are trying to meet is the 2040 or earlier target, which is in the transition plan, which is referenced in the papers," Mr Steel said.
Mr Steel said a zero-emission transition plan for the Transport Canberra fleet would be published by the ACT government "very soon".
A September 2020 transition plan included a target of a "minimum" of 80 electric buses to be on the road in 2024-25.
The government in April defended bus advertising that said electric buses were "1 of 106" when only 12 of the vehicles were on the road.