The government set a target of emissions being 40 per cent below the 1990 level by 2020. But they are currently 26 per cent higher than 1990, and rising.

But Climate Change Minister Shane Rattenbury said emissions would begin to steeply decline from next year as more ACT-funded wind farms begin operating.

"From next year, another large portion of ACT procured clean energy generation will come online, helping commence the dramatic decrease," he said, tabling the latest greenhouse gas report on Thursday.

Mr Rattenbury is confident the 2020 target would be achieved on time.

"The modelling is clear that with 100 per cent renewable electricity we will achieve the 40 per cent target," he said. "The amount we are purchasing will get us to that point."

Canberra's target for 2020 is 1918 kilotonnes of carbon dioxide. In 2015-16, emissions were 4017 kilotonnes, up very slightly on the year before.

That means emissions will need to more than halve in just four years if the government is to meet its target.

Per head of population, the picture is improved. Each Canberran contributed an average 10.22 kilotonnes of carbon dioxide in 2015-16, down from 10.31 on the year before, and down from 11.45 kilotonnes in 1990.

The biggest contributor is electricity and gas, contributing almost two-thirds of the total.

Householders used slightly more electricity in the most recent year, which the report puts down to population growth and a shift from gas to electricity in heating.

But the increase in renewable energy resulted in an overall decrease in electricity emissions, down 1 per cent to 2211 kilotonnes.

In 2015-16, 21 per cent of the city's electricity was powered by renewables, from the government's funding of wind and solar farms, and from rooftop solar.

The government promises 100 per cent renewable energy by 2020.

Transport remains a problem. Transport emissions increased 4.8 per cent in the year, with higher use of petrol and diesel.

Emissions from waste increased by 15 per cent, mostly from landfill. The report described these as "legacy emissions", from the breakdown of waste sent to landfill in past years.

Mr Rattenbury said the report showed emissions had "stabilised" and "decoupled" from population growth and economic growth.

Mr Rattenbury said with the hard work on electricity done, the government needed to tackle the more difficult areas, especially transport, waste, gas and buildings. Light rail would start the work on transport emissions but was not the only answer.

Two of the ACT-funded large-scale renewable projects were producing electricity this year - the Royalla solar farm south of Tuggeranong, and the Coonooer Bridge wind farm in Victoria, which between them produce 37 gigawatt hours. Rooftop solar had increased from 66 to 89 gigawatt hours.

"This increase in renewables offset the slight increase in demand of electricity between years and demonstrates the importance of this policy in reducing ACT's emissions," he said.

This year, the government brought forward its zero emissions target by 10 years, to 2050.