Australia will fall short of its Paris carbon reduction targets signed under Tony Abbott unless it lifts its renewable energy production to levels higher even than Labor's plan for 50 per cent green energy reliance by 2030.
The first assessment by the Australia Institute's new Climate and Energy Program, to be released on Monday, has found that unless a higher burden is placed on the more expensive process of carbon reductions in other sectors - agriculture, transport and manufacturing - then the electricity generation sector will need to aim for a renewable energy target of at least 66 per cent by 2030, and possibly as high as 75 per cent.
That is, a power generation sector where the fossil fuel component is reduced to perhaps a quarter of the size it is now.
Power generation currently accounts for 35 per cent of total emissions, which is twice as much as the next biggest contributor, fuel combustion and transport, at 18 per cent.
Industry produces 14 per cent and agriculture 13 per cent.
The current emissions reduction target, committed to in Paris while Mr Abbott was prime minister, is 26-28 per cent lower than the 2005 level - part of Australia's contribution to a global effort to restrict the planet's temperature increase this century to no more than 2 degrees Celsius.
The government is now wrestling with how to go about this after Chief Scientist Alan Finkel proposed a clean energy target which would lock in a 28 per cent reduction in energy-related emissions by 2030 through a four-pronged strategy emphasising energy security, reliability, affordability for households and business, and meeting Australia's emissions targets.
Last week Mr Abbott indicated he would cross the floor in Parliament to stop further renewable-friendly policies, calling it "unconscionable for a government that was originally elected promising to abolish the carbon tax and to end Labor's climate obsessions to go further down this renewable path".
The comments underlined the bind faced by the formerly green-tinged Prime Minister Malcolm Turnbull.
Along with Energy Minister Josh Frydenberg, Mr Turnbull has been working feverishly behind the scenes to settle a CET in official policy by the end of the year, although his government's febrile internal politics now look like producing a watered-down and renamed version designed to foster a new so-called high-efficiency, low-emissions coal-fired power station.
However, the Australia Institute, which has taken over the intellectual property of the Climate Institute, says even Dr Finkel's model would be insufficient on its own to meet the international obligations signed under Mr Abbott.
"This analysis of the economic modelling demonstrates meeting these targets for the electricity sector with a policy like the clean energy target is likely to require 66-75 per cent of electricity to be supplied by renewables," said Australia Institute executive director Ben Oquist.
This was because a CET "provides less of an incentive for gas generation than an EIS (emissions intensity scheme) or a carbon price".
Mr Oquist said the country was at a "critical juncture" and government must decide if it is to meet its commitments in the cheapest way, which is through greater renewable energy dependency than currently envisaged, or by demanding the more expensive and disruptive changes required in other parts of the economy.
"If Australia adopts a weak clean energy target which does not provide a strong signal for renewables, we risk turning Australia's moderate Paris targets into an extremely expensive task," he said.
"It remains to be seen if we choose to meet those Paris commitments the easy way or the hard way."
The discussion paper was written by the institute's director of research, Rod Campbell, who described it as ironic that government-commissioned modelling showed that policies that would actually "minimise renewable energy penetration such as carbon pricing and an emissions intensity scheme have already been rejected".
"All that remains is the CET that would bring in the largest share of renewable generation, or the prospect of failing to meet our Paris climate targets," he said.
Acting Labor leader Tanya Plibersek said the solution to a 10-year political standoff on climate policy was within reach because Labor had signalled that it would "cop" a CET.
"We don't think that is the No.1 approach, but as the No.2 approach we are happy to compromise with the government to introduce a clean energy target," she told the ABC's Insiders.
"The problem is not the gap between Labor's position and Malcolm Turnbull's position, the problem is all inside the Liberal and National parties where they've got a determined small rump of people who are absolute wreckers when it comes to greater investment in renewable energy," she said.
"This government is in its fifth year, we've seen seven coal-fired power generators close down, taking 4,000 megawatts of baseload power out of the system and nothing replacing it. That's a real problem."
Last week, Mr Abbott proposed ending all subsidies on renewable energy as a political strategy for positioning the Coalition.
"This is an opportunity for us to sharpen the difference with Labor on an issue which is of deep concern to the public, on a hip-pocket issue where we can be on the side of voters and Labor is on the side of green extremists ... let Labor be the party of renewable energy and us the party of reliable energy," he said.