Mr Rattenbury introduced draft laws to bring forward the territory's zero emissions target by five years to 2045 on Thursday, with the caveat that the full cost of cutting greenhouses gases was unknown at this stage.

"The answer will ultimately depend on changes we see in the future, such as developments in national energy policy, and how much behaviour change can occur from community leadership," Mr Rattenbury said.

"We have undertaken some work on costs. The ACT government engaged a consultant to analyse the costs of achieving the 2030 interim target.

"Their report suggests that a 65 per cent reduction on 1990 emissions can be achieved by 30 June 2030 at an estimated cost of $5.8 million."

But Mr Rattenbury said the cost of tackling climate change now is better "than the costs we will have to pay for inaction".

"If we wait, we will be playing catch up in dealing with issues like stresses on the health system brought about by extreme heat, and replacing locked in infrastructure that has both a negative effect on our climate, and isn’t built to cope with the impacts of climate change," Mr Rattenbury said.

"Businesses will also have additional costs, such as lost employee productivity. These benefits of taking action now are known as co-benefits, and we have the opportunity to grasp them now or miss them.  Tackling climate change now makes economic sense for governments, businesses and the community."

The revised target was a recommendation of a Climate Council report last year, which also called for interim targets to help the ACT meet its deadline.

The interim targets that will be adopted are a 50-60 per cent reduction on 1990 emissions by 30 June 2025; 65-75 per cent less by 30 June 2030; and 90-95 per cent less than 1990 emissions by 30 June 2040.

Mr Rattenbury has said before said the ACT will meet its existing target of 40 per cent reduction target in 2020 because of the transition to 100 per cent renewable energy. Electricity accounted for 57 per cent of carbon emissions in 2012-13.

The difficult target to meet will be the reduction of 50-60 per cent by 2025 because it will rely on a drop in transport and natural gas emissions.

However Mr Rattenbury said climate-friendly technologies were becoming more affordable, which would make them more attractive than their higher-emitting counterparts.

" The price of wind and solar is reducing, and households are finding that they can achieve major energy savings through the use of solar panels," Mr Rattenbury said.

"More recent technologies, such as electric vehicles, are also dropping in cost and will eventually be cheaper than their high emitting alternatives. In other words, such technologies will be business as usual."