Australia's biggest cities are setting ambitious targets to cut carbon emissions despite signs the Federal Government will wind back the Renewable Energy Target (RET).

The review into the country's RET is expected to make its recommendations next week.

But when it comes to going green, Melbourne and Sydney are on the same page and are determined to make it happen, whatever direction the Federal Government takes.

The cities are rolling out solar panels, installing LED light systems and designing energy efficient buildings.

Sydney plans to reduce its emissions by 70 per cent by 2030 while Melbourne aims to have zero net emissions in just five-and-a-half years.

City of Melbourne councillor Arron Wood says environmental action is at the forefront of everything the council is doing.

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"We're certainly making big inroads, but to reach that goal by 2020, there's some pretty big numbers," he said.

"[But] I am absolutely vehemently opposed to any relaxing of the renewable energy target. It's done wonderful things in terms of renewable energy investment.

"Interestingly enough we talk about the cost that renewable energy targets add to people's bills, but when you look at the wholesale cost, it's one of the only measures which is actually putting pressure on wholesale electricity prices."

Renewable energy key factor in reducing emissions.

Sydney's goal is to produce 70 per cent of its electricity needs from tri-generation, a more environmentally friendly, low-carbon production method with solar and wind power making up the rest.

Melbourne is aiming for a renewable energy contribution of 50 per cent.

"Really, you do have to have a large proportion of your energy mix coming from renewable to have a hope of reaching that target," Cr Wood said.

"Even the Urban Forest Strategy, which is about cooling our city: we've got a target of doubling the canopy cover in the city by 2040.

"That's really about decreasing ambient temperatures and meeting the urban heat effect. But what it does is, it also makes the city look good."

Sydney's Lord Mayor Clover Moore says any change to the target will make Sydney's goal more difficult to achieve.

"It's much better if the national Government is also committed to taking action on climate change," Ms Moore said.

"We already know with the winding back of the carbon pricing that it's making it harder to achieve our tri-generation precincts in Sydney. So that would have an effect."

Ms Moore says the steps being taken have the community's full support.

"We are the most urbanised country in the world and we know that our cities are where 70 per cent of emissions occur," she said.

"I think it's really incumbent upon city leaders to commit to taking this action and follow through on it."