Leaving nuclear is not without its critics, especially among big utilities: Sweden's Vattenfall is reportedly suing the German government for €4.7 billion ($6.9 billion) to compensate for its losses.

And yet, German policymakers seem determined to stick to an ambitious – and unilateral – goal of slashing greenhouse gas emissions by 40 per cent on 1990 levels, even if that means shutting near zero-carbon nuclear plants along the way. The cuts deepen to 55 per cent by 2030 and 80-95 per cent by 2050.

The country is also betting big that renewable energy mainly from wind, solar and hydro power will continue to surge beyond its current share of about 28 per cent of total supply.

That ambition contrasts with the Abbott government's push this week to get its 20 per cent reduction of Australia's 2020 Renewable Energy Target through the Senate. The current bipartisan goal is a 5 per cent cut of 2000 levels, also by 2020, with the government likely to release its longer-term targets next month.

Little wonder, then that German officials label Australia as a "black sheep", with generally unhelpful participation in diplomatic wrangling ahead of the Paris climate summit at the end of the year. They also see huge market benefits from their nation emerging as a "green superpower".

"It's an issue of protecting the environment and climate," Volkmar Klein, a member of the German parliament from the Christian Democratic Union, the right-of-centre party led by Chancellor Angela Merkel that dominates the ruling coalition. "But at the end of the day, if we are able to manage it successfully, it will be the next step of gaining competitiveness.

"[If] we use mainly renewable energies, that will be a very, very big advantage – and 'green superpower' means exactly this," says Klein, who previously worked in German's famed "Mittelstand" – the small and medium-sized companies that form the backbone of the export powerhouse.

Not that Germany's commitment to shuttering nuclear plants has always run with precision.

After securing a second term as chancellor in 2009, German Chancellor Angela Merkel introduced a "phase-out of the phase-out" of nuclear energy only to revert to the original 2000 policy launched by her predecessor. the Social Democrat-Greens coalition, after Japan's Fukushima nuclear disaster in 2011.

Unease about nuclear energy runs deep in Germany, not least because it was in the front line of the Cold War.

The country, divided into a pro-US western region and Soviet-controlled east from the end of World War II up to reunification in 1990, was a presumed nuclear battlefield in any outbreak of hostilities, says Andreas Kraemer, founder and director emeritus of the Ecologic Institute, a Berlin-based think tank.

The dramatic plunge in renewable energy prices – with solar panels becoming about 20 per cent cheaper for every doubling of output – has undermined whatever business case existed for nuclear energy, Kraemer says.

"Solar is competitive with new coal and new nuclear [power plants], and even with old coal if you price the carbon emissions properly," Kraemer says.

Germans freely admit that overly generous feed-in tariffs paid to those supplying renewable energy to the grid meant the country paid billions of euros too much to install solar panels on the roofs of some 3.5 million homes and small businesses in a country not known for its bounteous sunshine. Sunshine hours in Berlin, a relatively northern city, peak at an average of eight hours a day in May-July, but drop to just one hour by December, according to a local tourist guide.

The levy now costs users 6.17 euro cents (9¢) per kilowatt-hour, boosting residents' costs for power to about 26 euro cents/KW-hour. [By contrast, this correspondent pays about 31¢ in Sydney for 100 per cent renewable power.]

The subsidies underpin Germany's Energiewende, or energy transition, a policy which is gaining international attention. The term is apparently the most commonly searched-for German word, eclipsing angst and blitzkrieg, according to one local supporter.

Renewable energy's share of the country's total electricity supply has almost quadrupled. Nuclear's share has roughly halved over the same period from 27 per cent to about 14 per cent.

The Grafenrheinfeld nuclear plant closing this weekend will take another 1.345 gigawatts of capacity off the market. The plant, built in 1981, produced about 1.6 per cent of the country's total power output last year, Reuters reported.

However, the Energiewende is not without its teething problems. Improved energy efficiency – which means bills fall even if unit prices rise – in homes and businesses mean energy demand is weak or falling, resulting in rising German power exports.

The way wholesale prices are set – as in Australia, renewables' zero cost of fuel knocks down the price all suppliers receive – means cheaper coal can displace expensive gas, lifting the sector's emissions in Germany and neighbours such as the Netherlands.

A policy fix to find ways of charging coal-fired plants more to force older, less-efficient stations to shut down, is now the focus of intense debate. Merkel has left the mess to her economics and energy minister Sigmar Gabriel, who also happens to be her most likely rival as chancellor at the next polls in 2017.

Gabriel is having to face resistance from the remaining tens of thousands of coal workers who may be out of work in two regions in the west and east. By contrast, renewable energy jobs have increased to about 350,000 under the transition policy, government officials say.

Despite the political wrangling, Merkel appears committed to climate action.

As host of this month's Group of Seven summit in Bavaria, the chancellor steered the leaders to a total elimination of carbon from the electricity sector this century, arguing such a move was vital if the world was to keep global warming to within 2 degrees of pre-industrial levels.

Professor Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research, says Merkel – herself also a theoretical physicist by training – has understood the risks of climate change since she was a federal environment minister in 1994 hailing from the former communist East Germany.

Even in the wake of the failed Copenhagen climate summit in 2009, Merkel brushed aside Professor Schellnhuber's readiness to counter sceptics' claims that climate change wasn't real.

"It was almost disappointing to me. I tried to explain to Merkel but she said, 'I don't want to hear it. This is crystal clear to me anyway,'" he said.

Likewise, she remains convinced Germany has to switch from fossil fuels to renewables, or as some officials said, would you bet against German industry?

"'This is a no-brainer to me, but tell me rather what we can do about it," Professor Schellnhuber recalls her as telling him.

Seated in the same Potsdam room that Albert Einstein discussed his theory of relativity in 1916 with fellow pioneers like Karl Schwarzschild that helped lead to modern telecommunications, Professor Schellnhuber said the history of the Industrial Revolution offers pointers to what's ahead for energy.

"Can anybody imagine that you can operate two completely different economies – one based on fossil fuels and nuclear, and the other based on efficiency and renewable – in parallel for the next five-six decades? It is ludicrous, it will never happen," he said. "All the history of industry tells us that once the system gets tipped to a new mode, and you have some comparative advantage, it takes it all, of course."

Peter Hannam was a guest in Germany of the country's foreign office.