Canberra must now reduce its net emissions to zero by 2045, 15 years earlier than the original carbon neutrality date.

That deadline was brought forward by a decade in 2016 by then climate change minister Simon Corbell, when he announced the ACT's move to 100 per cent renewable energy by 2020.

It's that shift that will enable the ACT to meet its first interim target of a 40 per cent emissions reduction on 1990 levels by 2020, climate change minister Shane Rattenbury said.

Mr Rattenbury said while the ACT's carbon levels were still above 1990 levels two years out from the 40 per cent reduction target, they would drop dramatically in the next 12-18 months as 300-400MW of renewable energy came online.

"We will definitely make the 2020 target," Mr Rattenbury said.

The latest inventory put the ACT's carbon emissions at 23 per cent above 1990 levels, with about half of the territory's electricity coming from renewables.

In 2018-19, 77.7 per cent of the ACT's power will be green. In 2019-20, it will be 96.6 per cent before reaching the 100 per cent target in 2020-21.

The targets were a recommendation of a Climate Council report last year detailing how the ACT could meet its climate targets.

The report recommended the interim targets, but warned the ACT against buying carbon offsets from abroad to meet them.

Mr Rattenbury confirmed the government had not yet made a decision on whether to heed the Climate Council's warning, but said it was his preference that the ACT did not offload its carbon commitments to other nations.

"The community broadly supported that [preference] although we will do some more analysis of the feedback," Mr Rattenbury said.

Mr Rattenbury said the targets had been released before the issue of buying offsets had been resolved because there was policy work under way in the transport and planning spaces that would ultimately affect the ACT's ability to meet the targets.

"That's the beauty of the interim targets, they will hold us to account," Mr Rattenbury said.

Mr Rattenbury acknowledged the 2025 target would be harder to meet, as transport and natural gas consumption will become the biggest contributor to the ACT's carbon emissions once all electricity is sourced renewably.

Reducing those emissions will require a behaviour change from consumers, a shift that will be harder to manage than setting a 100 per cent renewable energy target.

However Mr Rattenbury said work was already under way to make that change happen, with a new electric vehicles strategy launched last month, and construction on Canberra's first gas-free suburb beginning.

Through a public feedback process, people also made more than 1500 suggestions on how the ACT could reduce carbon emissions.

Those suggestions will be collated into a report that will be released later in the year.