02/09/2020 - 14:59

20-year payback for batteries

02/09/2020 - 14:59

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It will take 20 years for homeowners using a Tesla Powerwall to recoup the purchase cost under a new solar pricing scheme, a recent analysis has found.

20-year payback for batteries
Homeowners will earn a higher price for solar when it is most needed in the grid. Photo: Gabriel Oliveira

It will take 20 years for homeowners using a Tesla Powerwall to recoup the purchase cost under a new solar pricing scheme, a recent analysis has found.

The Distributed Energy Buyback Scheme will pay homeowners more for selling solar power during peak demand times between 3pm and 9pm, while payments during other parts of the day have been cut.

Business News revealed the change last week, with the state government announcing on Monday that homeowners with existing solar panels will remain under the current Renewable Energy Buyback Scheme.

The move is designed to reduce pressure on the grid during the day, when voltages rise because rooftop solar is producing so much energy.

Analysis from South Australian comparison website Solar Quotes said the changes would delay payback of a new 6.6 kilowatt system by 10 months, to be about 4.5 years.

But modelling from Energy Policy WA arrived at a different figure, with a payback within 3.3 years, compared to 2.7 years under the old scheme, assuming a 5kW system costing $3,000.

Rooftop solar would remain an attractive investment, a spokesperson for Energy Minister Bill Johnston said.

Solar Quotes' numbers suggest the cost of a Tesla Powerwall 2 would be paid back over 20 years, rather than 22 years under the old scheme.

The company's modelling also assumes the retail electricity price will grow at 3 per cent per annum, reflecting inflation, and does not discount cash flow.

That implies the payback period may be longer than forecast.

Solar Quotes founder Finn Peacock told Business News the changed pricing structure might push people marginally towards batteries.

“It’ll certainly make them think about when they use their electricity, that’s for sure,” he said.

“We’re grappling with this [grid challenge] in South Australia as well … WA is in a unique position with a standalone grid.

“If Australia wants a high penetration of renewables including solar, there has to be a mechanism to switch off solar in the middle of the day in emergencies.”

SA announced a move on that front in recent weeks, with Mr Peacock saying WA will eventually need to head the same way.

Power Ledger chair Jemma Green said the DEBS was a positive change because it more accurately reflected the price of electricity in the wholesale market.

But she said there was a lost opportunity.

“Technologies that facilitate peer to peer energy trading can deliver the same system outcome as the DEBS but without taxpayer subsidy,” Dr Green said.

Power Ledger ran an energy trading trial with Synergy and other stakeholders in the City of Fremantle, which found dynamic pricing would encourage more shifting of demand.

“Customers in our Renew Nexus P2P trading trial in Perth said they would be three times more likely to buy a battery if they could trade energy,” Dr Green said. 

“This shows that market mechanisms can achieve system outcomes required without government subsidy.”

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