Academics are excited by the promise of Tesla's Powerwall but believe it could be a decade or more before users can think about disconnecting from the fossil fuel reliant electricity grid.

Tesla CEO Elon Musk unveiled the Powerwall rechargeable lithium-ion batteries on May 1, which come at a cost of between US$3000 and $3500, excluding installation.

Users can charge them using rooftop solar, or at times when grid consumption rates are low, "discharging during more expensive rate periods when electricity demand is higher".

Tesla is hardly first in the home energy storage space, but its entry into the market is seen as important for the technology to gain critical mass.

"Powerwall is important because of the global brand of Tesla," Delta Electricity chair in sustainable energy at the University of Sydney, Professor Anthony Vassallo, told an Australian Science Media Centre briefing.

"It's a bit like the iPhone level of consumer interest. If it were a different company offering the same product you wouldn't have gotten that publicity."

Associate Professor Iain MacGill, joint director (engineering) of the Centre for Energy and Environmental Markets (CEEM) at UNSW, concurs.

"Is there hype involved [in Powerwall]? Yes, absolutely, and that's Tesla's way," MacGill said, noting that hype "can change the market".

"Is it revolutionary? I think perhaps, but it's too soon to tell. Even if it isn't revolutionary it can still start driving some pretty fundamental changes and that's important".

Solar sweet spot

The 1.4 million or so households that currently run rooftop solar are an obvious market for the Powerwall (and its rivals).

Presently, excess solar power that solar households generate is sold back to the grid at a substantially lower price than what is paid to consume electricity from the grid - and that hasn't gone unnoticed in Tesla's Australian marketing efforts.

MacGill said that retail tariffs to consume from the grid could be "around 25 to 30 cents per kilowatt-hour" - but excess solar put into the grid might fetch as little as six cents per kilowatt hour.

It makes better financial sense for rooftop solar owners to be able to store excess power and "self-consume" it later, rather than sell it to the grid for cheap.

"Energy storage to save up your photovoltaic energy and self-consume it later in the evening rather than exporting it to the grid could be pretty valuable," MacGill said.

Jemma Green, a research fellow at the Curtin University Sustainability Policy (CUSP) Institute, agreed that battery storage could appeal to people who believed they were getting a raw deal on price from the utilities.

"In Australia I think there's a perception that electricity prices have gone up far too much," she said. "I think people are feeling like the utilities aren't really giving people a fair go and that that may also be a driver for changing demand [for grid power]."

Grid dependency

While Tesla has been pushing hard on the idea that mass Powerwall adoption could allow us to pull back from the grid, Australian academics are cautious on the extent to which the technology makes this possible - and on the idea itself.

"It's still very early days to see whether this type of technology actually will allow people to become more or less grid independent," Vassallo said.

"My own analysis here, and of my team, is that we're a long, long way from getting to that point where people will find a satisfactory performance after installing storage and disconnecting from the grid."

MacGill said that the possibility of leaving the grid forever was open to only a "fairly small number" of energy users.

"You've got to be really cautious about trying to think about what it actually means to leave the grid," MacGill said.

"The grid's a pretty valuable asset because of the service it provides, and you shouldn't underestimate the costs and challenges of going off grid."

Green did not believe that energy storage adoption would lead to such a black-and-white view of grid dependency.

"I don't think we're going to have an all-or-nothing scenario where we're either on-grid or off-grid," Green said. "I think it's more nuanced than that.

"Solar has seen the erosion of the demand and full utilisation of the grid when the sun is shining, and what batteries will do is erode the diurnal - the night time - part of the market."

Even if people remained somewhat grid-dependent in the future, mass adoption of home energy storage systems could prove useful.

"The good news is even if it doesn't make sense to go off-grid, if the existing [energy] businesses work too hard to collect money from you even as you're using less and putting in storage and assisting in managing networks and so on, it does sort of provide a discipline," MacGill said.

"It's helpful to have an alternative if the existing players behave too badly."

Limited by scale

One of the limitations of the Powerwall, however, is the size of the systems being offered.

"The size of the unit is such that really in Australia it's not enough to ride you through a day or a couple of days of bad weather," Vassallo said.

He saw that as a limitation on the mass adoption of the technology in Australia but overcoming it could usher in a new era for renewable energy use.

"I don't think [Powerwall adoption] is going to be the end of the fossil fuel industry by any means, but it's certainly going to make it more acceptable and more feasible to install greater and greater amounts of renewable energy," Vassallo said.

"The more energy storage you can get into the network, the easier it is to keep incorporating more renewables, so it really does open up the electricity market to greater and greater amounts of renewable energy.

"But you need a lot of storage, and we're well short of that sort of scale at the moment. Possibly in five or ten years, there would be enough there."