In Western Australia, you can feed in more than 10 times as much power to the grid as you draw, and still end up with a bill.
But the low buyback rates are likely to stay, as the energy grid faces an enormous transformation.
Where rooftop solar once delivered healthy credits to households who fed their excess power back into the grid, feed-in tariffs have been slashed in recent years, meaning new adopters are likely to end up with a bill, even if they export more power into the grid than they draw from it.
The ABC has seen one bill of a resident who exported 2,186 kilowatt hours (kWh) over summer, drawing only 186kWh from the grid, who was still left owing money to Synergy after supply charges.
That's because while power drawn from the grid attracts a charge of 27.32 cents per kWh, energy fed back into the grid by a new customer attracts a rate of 10 cents per kWh between 3pm and 9pm, and just 2.5 cents per kWh outside of those hours.
Householders who got rooftop solar before August 31, 2020 can still access the more generous Renewable Energy Buyback Scheme (REBS).
Era of generous rebates over
It's a far cry from just 10 years ago, when early adopters of rooftop solar were paid 40 cents per kWh, effectively allowing them to run profitable home power stations and generate huge credits to repay their initial investment.
Fraser Maywood, chair of WA research and advocacy group Sustainable Energy Now, said the high feed-in tariffs had been highly effective.
"Initially feed-in tariffs were a means for encouraging people to put rooftop solar on and to stimulate the market," Mr Maywood said.
"That has been very successful – more successful than was anticipated.
"It has driven a societal change in terms of people seeing more of their neighbours get rooftop solar and changing people's opinion, driving an exponential uptake."
More than 460,000 WA households now have small solar units — about 30 per cent of homes — making their combined output the largest power station on the South West Interconnected System (SWIS) grid.
Mr Maywood said it was unlikely feed-in tariffs would increase because the incentives were no longer needed.
"People were paying $20,000 for a 3-kilowatt system 20 years ago, so there needed to be some incentive for them to install it," he said.
"With the price of solar panels dropping, you can get a 12-kilowatt system for around $12,000, and that's got a significant impact on your bill, so the incentive is no longer required."
Focus shifts to battery storage
Mr Maywood said the state government's focus should now be on developing storage, so it could make better use of the cheap and abundant energy flowing from rooftops, as well as educating consumers about ways to manage peak demand.
The changes WA will need to make to de-carbonise the grid will require consumers to learn to use electricity differently, including making the most of the power they are generating on their rooftop units themselves.
"Previously, [energy] was a box on the wall that some person came and read once a quarter, you turned the switch on, the lights came on, and you didn't have to worry about it, everything was taken care of," Mr Maywood said.
"There really needs to be a lot more education done with the public about energy efficiency, time-of-use charge, and demand side management, which has a very big role in a future smart grid."
He said encouraging people to make small changes in their use could make a huge difference.
"[One thing] the government could look at, especially in the transition, because the transition is actually quite a fragile time, would be to reduce power using a combination of smart meters, smartphones and SMS messaging.
"You could ask people to reduce loads and be given an incentive to do that."
Powering homes from an EV
The other thing Mr Maywood suggested governments could do was to look at ways to support the use of electric vehicles as home batteries through the use of bi-directional charging – whereby the power stored in an EV battery could be fed back into households or the grid.
"People who have EVs are early adopters, they're your rooftop solar people from 20 years ago, so you really want to try to encourage them and remove barriers for them to use batteries in the vehicle to leapfrog home batteries," he said.
"An EV battery size is typically five times that of a home battery.
"The battery supply chain is constrained — lithium and other materials being directed preferentially into vehicles rather than stationary storage would be a smart move."
Low tariffs 'unfair on households'
Peter Newman, professor of sustainability at Curtin University, is scathing of the "slow pace" at which WA authorities have developed battery storage.
"[Households] are virtually getting nothing back from providing this energy into the system," he said.
"That, to me is very unfair, but it's also not good engineering, it is not getting near the solution.
"If the storage was there, if we'd been buying up batteries and getting them going, then we would have had a system where the solar coming in could be stored and used when needed, which is a smart, sustainable system."
But he said while the feed-in tariffs were low, rooftop solar was still a worthwhile investment simply for the amount customers could save by using their own power as much as they could during the day, without worrying about their bill.
"Two-point-five cents, it's just nothing, and that's not going to pay back your investment," Professor Newman said.
"But what will pay back your investment is the lack of power that you need [to use from the grid] during the day when the solar is pumping out.
"In Western Australia, we've got all the sun, it's still very cheap. We're doing our bit well, but the state government utility really needs to get a move on with storage systems."
