SYDNEY — One of the first owners of the new Tesla Powerwall 2 home battery has used a formula to calculate that he will have a $0 electricity bill by using the battery.
The Powerwall 2 is the latest generation battery released March in Australia, which at the time prompted Atlassian’s Mike Cannon-Brookes to place a highly publicised bet with Tesla founder Elon Musk to solve South Australia’s blackout woes.
Brendan and Josephine Fahey’s house, in the northern Melbourne neighbourhood of Coburg, is the first to have the Powerwall 2 system installed in the city. It’s understood their case is one of the first deployments globally as well.
Brendan Fahey bought the new 14kWh battery to pair with his existing solar panels after carefully doing the sums to work out he could have a zero power bill.
“I did some calculations with Powerwall 2 by writing a little formula based on my solar production and electricity usage for each day from 1st December 2016. Starting with a 14kWh home battery I subtracted and added on the gains and losses as I went through the six months up until a few weeks ago,” he said.
“At no point in my calculations did the 14kWh battery run out. If I had owned Powerwall 2 during that time I would have had no electricity bill.”
The Tesla website indicates a price of $8,750 for a Powerwall 2 and “supporting hardware” plus installation labour costing from $1,150 to $2,900.
There have been criticisms of the overall cost of the Powerwall 2, with SolarQuotes chief Finn Peacock saying in March that Tesla’s new battery was already “beaten even before the first deliveries”.
“A relatively unknown Australian company, Ampetus Energy, have released a 3kWh ‘Super Lithium’ battery retailing for $2,300,” Peacock told energy industry publication One Step Off The Grid.
“This is available to ship right now and beats Tesla with a cost-per-warranted-kWh of $0.19. This is mainly due to their 15 year warranty, which is also the best in the industry.”
Traditionally homeowners used the electricity generated from solar panels in real-time as it was provided or, if excess was harvested, could sell it back to the general grid. But with the feed-in payment rates fluctuating according to market forces and government regulations, and battery technology fast improving, storing the excess energy is starting to become an alternative.
Last September, Business Insider reported a Gold Coast man that installed six 6.4kWh batteries of Tesla’s previous Powerwall 1 model to become completely self-sufficient.
Savings in the early days of the Powerwall were reportedly nowhere near enough to offset the cost of equipment and installation. In 2015, Lifehacker Australia calculated that with a maximum saving of $1.06 a day for a Sydney residence that charged its battery during off-peak hours, the system needs to be used for 25 years to reach break-even.
Fahey said that for him the financial savings wasn’t the only motivation in buying a very expensive battery.
“My motivation is to get my electricity bill as close to $0 as possible, and for the good of the environment,” he said, adding that blackout contingencies can be planned for in real time with the Tesla app.