Earlier this year, the Coalition made a curious, significant move.
David Littleproud, the leader of the National Party, broke cover and wholeheartedly threw his support behind rooftop solar and household batteries.
The Nationals, he said, were not against renewable energy, only large-scale projects such as wind farms and transmission lines that were "tearing up the environment".
Quite the opposite – the National Party wanted as many Australian households to get solar and batteries as would have them.
The pitch, which was quickly backed by Opposition Leader Peter Dutton, evidently had a few purposes.
For starters, it clearly distinguished the opposition from the Labor government, whose plan to decarbonise the power system rests largely on big-ticket renewable energy and transmission items.
In one fell swoop, the Coalition was able to say it was pro-renewable energy while being able to attack the government's own green plans as environmentally and economically dangerous.
What's more, the shift was a clear nod – or a sop depending on who you ask – to the enormous and growing political clout of Australia's solar-owning class.
Lastly, as both Mr Littleproud and Mr Dutton have repeatedly since pointed out, rooftop solar was an ideal complement for the central plank of the Coalition's energy plans – nuclear.
Dangers in the detail?
The thinking behind that pivot has been on full display in recent days after the Coalition finally unveiled the major details of its energy policy for the upcoming federal election.
Under the plans, Australia would get seven nuclear power plants by the middle of the century – five large-scale ones across New South Wales, Queensland and Victoria and two small ones across South Australia and Western Australia.
No longer would the renewable emphasis be on scores of new wind and solar farms in regional areas and the high voltage power lines needed to plug them into the grid.
It would instead be directed towards people's rooftops, "an environment that you can't destroy" according to Mr Littleproud.
But hiding behind this veil of logic from the Coalition, energy experts reckon, is a potentially fatal flaw.
Solar power and nuclear power don't play nicely together.
"That's another untested and questionable part of this whole strategy," said Dylan McConnell, a senior researcher and energy analyst at the University of NSW.
"What happens if we look into a system that is largely dominated by … a significant proportion of … behind-the-meter solar?
"People are going to continue to install rooftop solar and, in fact, the Coalition is supportive of that.
"Nuclear will have an economic challenge to operate in that environment."
At the heart of this tension are the differing – and some argue incompatible – characteristics of nuclear and solar power.
On the one hand, nuclear reactors are the quintessential base-load generators that can – and want to – run at or near full capacity all the time.
Not only are they well suited to the task technically, nuclear plants also have an economic imperative to operate flat-out given their monumental development costs.
These development costs are typically exacerbated by very long lead times – lead times subject to significant blowouts – in which debts are incurred and eye-watering amounts of interest can accrue.
The hare and the tortoise
Paying off those debts is paramount for the owner of a nuclear plant.
Failure to do so can be financially ruinous.
And the way to do that is to produce and sell as much electricity as is technically possible.
By contrast, solar power – specifically from photovoltaic cells typical of suburban rooftops – are the archetypal source of variable renewable energy.
They produce the most power when the sun is shining during the day, none when it's not, and their output can be highly variable depending on the conditions.
Unlike nuclear, solar is also extraordinarily cheap, at least up front, and large-scale projects can be delivered for comparative peanuts – and with blinding speed.
For a household, the cost of a 10 kilowatt system – an installation capable of meeting much of an average customer's needs – can be done for a few thousand dollars.
In other words, if nuclear power is the proverbial tortoise, solar is the hare.
None of which is to dismiss the technical and economic challenges that solar presents, namely, how to back it up when it's not producing – a very big task indeed.
But there is another crucial way in which solar and nuclear – or any base-load power such as coal, for that matter – clash.
Solar generation, by its very nature, peaks in the middle of the day.
As ever more Australians install seemingly ever more solar panels on their roofs, that peak in solar output is becoming truly epic in its proportions.
Rooftop solar is a beast
For example, there are times in South Australia where rooftop solar alone can account for more than the entire demand for electricity in the state.
To ensure South Australia's electricity system doesn't blow up, virtually all other generators have to pare back their output to a bare minimum or switch off entirely.
And even then, South Australia's surplus rooftop solar generation has to be exported to other states or wasted.
Rooftop solar can do this because it's largely uncontrolled and flows simply by dint of the sun shining.
It was partly for this reason that South Australia's only base-load coal plant retired in 2016.
Of course, there are many more times when rooftop solar provides precisely zero per cent of South Australia's power needs.
[Nuclear clash - Graph]But it all goes to illustrate the very real challenges that base-load nuclear would face, and the very real trends that are unlikely to grind to a halt between now and 2035, by when the Coalition hopes to have the first of its nuclear reactors up and running.
A quick glance at the numbers will tell you all you need to know about the popularity – and power – of rooftop solar in Australia.
There are now almost four million homes spread across the country with solar installations, and the electricity they generate accounted for about 12 per cent of Australia's needs last year.
Bruce Mountain, the director of the Victoria Energy Policy Centre, summed it up this way: "Rooftop solar has few opponents."
"It's the one thing that keeps on growing despite the impasse at a national level," Professor Mountain said.
"And I think there's much more to go to realise the potential for that, most notably on factory roofs."
Something has to give
Professor Mountain said "I'm kind of open to the idea of nuclear", noting that it was being taken seriously by many other developed countries seeking to decarbonise their electricity supply.
He also pointed out that Australia's development of large-scale renewable energy projects and, particularly, the transmission lines needed to support them, had hardly been a glowing success to date.
In any case, Professor Mountain suggested the fact the Coalition was proposing to own and operate any nuclear power stations was an acknowledgement that there was no commercial case for the technology in Australia.
On that point, Dr McConnell from the University of NSW agreed.
Dr McConnell said the economic obstacles in front of nuclear in Australia were enormous, and a big one was rooftop solar.
He said that in the almost inevitable event that nuclear and solar power clashed, something would have to give.
"The way you might achieve that in a system with lots of rooftop solar is by curtailing (switching off) rooftop solar," Dr McConnell said.
"And that may not be politically popular either."
Robert Barr, a power industry veteran and a member of the lobby group Nuclear for Climate, did not shy away from the potential for future tensions, noting that coal was already getting squeezed out of the system by solar.
But Dr Barr said any clash could be easily managed through a combination of price signals that encouraged householders to use more of their solar power and export less, and new reactor technology that could ramp up and down more effectively.
"You could probably drop down from 100 per cent down comfortably to like 60 per cent output and on a daily basis," Dr Barr said of new nuclear technology.
Ultimately, however, Dr Barr argued it may need to be households with solar panels that gave way to nuclear energy for the greater benefit of the electricity system.
Don't mention the solar wars
Right now, he said renewable energy was benefiting from taxpayer-funded subsidies that allowed wind and solar projects to make money even when the price of power was below zero dollars.
These subsidies applied to both utility-scale projects and rooftop solar panels, through the large- and small-scale green energy targets introduced by the Rudd Labor government.
They effectively allow such projects to sell their electricity for less than zero – up to a point – and still be in the money.
In the future, Dr Barr said, those subsidies would no longer exist and renewable energy projects would start to be penalised each time the price of electricity went negative.
"I think what will happen is that nuclear will just tend to push out solar," he said.
"There'll be an incentive for customers to back off.
"And I think it wouldn't be that difficult to build control systems to stop export of power at the domestic level.
"It'd be difficult for all the existing ones but for new ones, it just might require a little bit of smarts in them to achieve that particular end — it can be managed."
Much like the Coalition's grand policy pitch, those comments might be considered bold given the political heft wielded by millions of solar households.
Last decade, politicians of all stripes got into all manner of trouble when they tried to wind back subsidies known as feed-in-tariffs, which paid customers for their surplus solar power generation.
Solar households, egged on by the industry, mobilised, went on the attack and in many cases forced governments to bend to their will.
And that was at a time when the number of households with solar was a fraction of what it is now.
It's a constituency that politicians would tackle at their peril.
