When Australia's first community battery trial came to the Perth suburb of Alkimos Beach in 2016, Kelly was sceptical.
"There was a whole lot of discussion about whether it would save us money or not. The fee structure was quite complex," she said.
Eventually, her family took a punt and signed up to the trial.
A 1.1MWh lithium ion battery located in bushland on the edge of the suburb stored energy in the daytime, when rooftop solar panels were pumping out cheap and abundant watts, and released it into the grid in the evening, when residents came home and demand peaked.
Half a decade later, the Alkimos trial has finished (more on this later), others have begun elsewhere in the country, and community batteries are being promoted as a key part of the transition to clean energy.
If the cooperative local storage model works as well as advocates claim, quietly humming crate-sized batteries may become a familiar site in suburbs, towns and inner-city areas within the next five years.
Households should pay less for power, less for grid upgrades, and won't have to fork out thousands for a battery of their own.
But there are plenty of vocal doubters, with some saying this communal approach is doomed to fail.
So what are community batteries and are they better than home ones?
How do community batteries work?
The high uptake of rooftop solar has seen households generating remarkable amounts of cheap energy in the daytime, but created a new problem: congestion of the transmission network, or grid.
To understand this, think of the electricity as water and the network of wires and substations as pipes and pumps respectively.
The "water" generated by solar panels that households don't use has to be exported to the grid through these "pipes".
But if there's too much "water" for the "pipes" to transport, it backs up, and can "flood" (ie. overload) neighbourhood substations and households themselves, which damages appliances and infrastructure.
One solution is to install thicker wires and more robust substations to carry more electricity from the local network to the broader grid, but this is expensive.
It's also a bit of a circuitous route: the abundant solar energy that's exported to the grid in the daytime has to be sent right back again a few hours later, in the afternoon and evening, when people come home from work and use energy-hungry appliances like ovens and heaters.
Batteries can reduce grid congestion
Home and community batteries help solve this problem by storing the energy locally, so that less (or none at all) needs to be exported and then imported.
To use the water analogy, it's like having a big neighbourhood tank, or many smaller drums, to temporarily store the water.
A 1MWh battery can power up to 1,000 average homes for about two hours.
Though there are different models, households generating excess solar energy are typically paid to export this power to the battery, and then pay a smaller amount to import whatever they need later.
On top of this, there's usually a monthly fee to access the battery service.
All up, households are meant to save.
The 119 households that participated in the Alkimos trial, for instance, collectively saved over $81,000 on electricity costs over the five-year duration of the trial, or an average of about $36 per bill.
The battery also successfully eased the strain on the grid: there was an 85 per cent reduction in consumption of energy from the grid at peak times for participating households.
But the trial was too expensive to continue, the report concluded.
The monthly fee of $11 per household was "highly subsidised" and "not sustainable", meaning that participants were getting too sweet a deal and "the trial could not become a permanent offering".
But Synergy and Western Power, the two state utilities that ran the Alkimos trial, have since embarked on other larger community battery trials.
Synergy's general manager of customer experience, Colin Smith, said Synergy was exploring different "distributed energy resources" technologies including both home and community batteries.
For households, he said, "suburb-based batteries" are a "battery storage solution without the upfront costs."
Home batteries vs community batteries
Home batteries have proved relatively popular, with more than 30,000 sold in 2021, despite costing a hefty $10,000 for a standard-size system.
These small batteries are good for local energy storage, but a shared approach is more efficient, says Dylan McConnell, an energy systems expert from the University of Melbourne.
"The overall shape of the aggregate load and generation is better managed at [the neighbourhood] level than at the individual level," he said.
Individual households' energy generation and consumption partly cancel each other out at the suburb-wide aggregate level, which reduces the demand on the shared battery, he says.
"The sum of the peaks is greater than the peak of the sums.
Rather than many houses installing private batteries, the same number can use a shared battery at different times.
And the shared battery doesn't have to be as large as the combined capacity of all those household batteries, says Marnie Shaw from Australian National University's Battery Storage and Grid Integration Program.
"It's hard to give exact figures, but essentially you need less battery per house if you're sharing, compared to individual household batteries."
"How much less depends on a number of things, so it's hard to say exactly, but it's in the order of 10-50 per cent."
Shared battery trials are coming to a suburb near you
Western Australia has run the first community battery trials, thanks partly to not being part of the National Electricity Market (NEM), which means there are different regulatory hurdles: Western Power and Synergy kicked off a third trial for 600 homes early last year.
But the NEM is rapidly catching up: Ausgrid installed the "first of many" batteries in Sydney last year, as part of a two-year trial.
In Melbourne, United Energy has been rigging up a network of 40 small 30kW community batteries on power poles, to support 3,000 homes, following a trial in 2020.
And in May, Yarra Energy Foundation (YEF) will install a 250kWh battery in North Fitzroy.
This, too, will be the first of many batteries for inner-Melbourne, says Chris Wallin, YEF's commercial program manager.
"We have a goal of 200 community batteries within seven years," he said.
Community batteries, Mr Wallin envisions, will be a small, trusted, local service, "like a corner store".
"The second generation of batteries will include EV charging.
"Your EV will be connected to a charging point which will be connected to the community battery."
Community batteries one piece of the storage jigsaw
These mid-scale community batteries will exist alongside larger "grid-scale" batteries and smaller home ones, Mr Wallin says.
"We're not saying don't have home batteries.
Experts agree that Australia has to dramatically increase energy storage capacity in order to grow the share of renewables in the grid, decarbonise electricity generation, and have any chance of meeting our Paris Agreement emissions reductions targets.
YEF's plan for 200 community batteries barely scratches the surface.
The North Fitzroy battery, for instance, will service just one of the 5,000 "substation areas" that make up the CitiPower distribution network across Melbourne's CBD and inner suburbs.
That is, 200 batteries will cover a fraction of the CitiPower network, which itself is the smallest network in Victoria.
"Two hundred batteries is a drop in the ocean," Mr Wallin said.
Community batteries vs VPPs
Of course, there is a way to pool the resources of home batteries, to create a kind of distributed community battery.
Called a Virtual Power Plant (VPPs), it's a network of hundreds or even thousands of connected household batteries coordinated to work as one large virtual battery.
Whether community batteries or VPPs are the future will come down to a single question, says Hedda Ransan-Cooper, a social scientist with ANU's Battery Storage and Grid Integration Program.
"The question of trust is a really big one."
VPPs and other grid-integration schemes (such as vehicle-to-the-grid, or V2G, where EVs take the role of household battery) will only work with the participation of households that own what network operators call "distributed energy resources" — that is, the solar panels and home batteries themselves.
And to be willing to participate, they need to trust the grid-integration scheme is good for them, and not just for the company signing them up.
But Dr Ransan-Cooper has found "literally no empirical evidence" to support the idea that households want to participate, with many households saying this is because they fear the energy companies will try to rip them off.
"The energy sector is one of the least trusted," she said.
The general sentiment from interviews with households around the country, she said, was "don't mess with my kit".
"People don't like the idea of you coming in and fiddling with what's in their home."
Most VPP trials, she says, are heavily subsidised and made up of a demographic who are highly engaged and tend to be more willing to take the risk.
"That is a very small proportion of people."
Community batteries sidestep some of these trust issues, as there's no messing with kit, Dr Ransan-Cooper says.
They can also be operated by more trusted local organisations.
"Local government keeps popping up in the research that we do," she said.
The Yarra City Council, for instance, established the Yarra Electricity Foundation (YEF), which is now setting up the North Fitzroy battery trial and exploring the idea of residents becoming shared owners of their local battery.
Community batteries can also be used by all, not only those who can afford to buy a house and install solar panels and batteries.
"I'm a big fan of neighbourhood batteries," Dr Ransan-Cooper said.
"My personal view is [they] present a serious and much better alternative compared to household batteries."
But … some say it's a 'load of bullshit'
Tristan Edis, an analyst with Green Energy Markets, disagrees.
"It's a load of bullshit. People want to blow a bunch of money on this because they like the idea of socialism."
Having shared community batteries rather than batteries in everyone's homes may be a more efficient model of energy storage, he says, but it will never be done at a great enough scale.
Household batteries, he says, are what households want: the government should copy policy that has seen a world-record per-capita uptake of solar panels in Australia, and introduce battery rebates.
He's calculated that this would deliver 10,000MW of storage by 2030.
So far, however, there's no sign of a nationwide battery rebate on the horizon.
The Australian Renewable Energy Agency, meanwhile, continues to fund community battery trials (as well as VPP trials) — and Labor has promised to install hundreds of community batteries around the country if it wins the election.
The Victorian government has awarded millions in grants (including to the YEF) to "jump-start the rollout of neighbourhood-scale batteries" and the WA government, through Synergy and Western Power, is funding the PowerBank community battery trial across 12 metropolitan and regional locations.
Back in Alkimos Beach, the community battery has been taken away and Kelly is back on a standard power plan, which means she's wasting daytime solar energy and paying more for power than she had been.
She'd "definitely" sign up to another battery trial if one was offered.
But since one isn't, she's considering the alternatives.
"The trial does make me want to almost install a household battery," she said.
