Melbourne Man Says Powerwall 2 Will Drop His Power Bill To $0

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Melbourne's first Powerwall 2 has been installed at a three-bedroom, one storey house in Coburg. Brendan Fahey and his wife Josephine added Tesla's shiny new battery to their home to complement their existing solar panels, after Brendan calculated that the Powerwall 2 could take his energy bill down almost to zero.

Tesla's Powerwall 2 was announced in October 2016, a follow-up to the original Powerwall, launched in 2015. The new model has improved on the original in a number of ways. One of the biggest changes is a built-in inverter, where the original model required an external one. The Powerwall 2 almost doubles the capacity of its predecessor, upgrading from 7kWh to a full 14kWh (13.5kWh of which is usable capacity). With Australia's average household electricity usage estimated to be around 16kWh a day, or as low as 13.5kWh in Victoria, the Powerwall 2 is now offering enough storage for Aussie households to potentially offset their entire electricity bill, and perhaps even move off the grid.

This is what Brendan found when he crunched the numbers around adding a Powerwall 2 to his existing solar. "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," Brendan explains. "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. 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."

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Of course while Tesla and the Powerwall are big names in home energy storage, they're certainly not the only players on the field. One of the big stories the week of the Powerwall 2's launch pointed out that Tesla's shiny new battery had already been beaten on price by a competitor — an Australian made battery called the Ampetus "Super" Lithium. Based on SolarQuotes' solar battery comparison table, the Ampetus, a $2300, 3kWh battery has the lowest cost per warranted kWh of all the batteries currently on the market, at 19c. Tesla's Powerwall 2 is a close second at 23c per warranted kWh.

Taking into consideration the Powerwall 2's larger size and included inverter, which the Ampetus model doesn't include, the Powerwall 2 is still competing closely with the super cheap Australian model. For Brendan especially, the Powerwall 2's size was one of its biggest selling points. "The Powerwall was much cheaper than other batteries," he explained. "And at 14kWh it was a good size, which by my calculations would leave our power bills close to zero." The price was also a tipping point — with the improved model it was finally worth the investment. "I had considered batteries for a few years but they were too expensive. The new Powerwall 2 made my mind up."

Another key advantage to the Powerwall 2 over the original (or even over its competitors) is its integration with the Tesla app. While the app was originally designed just for Tesla's electric vehicles, it was recently updated with the capacity to connect to Powerwall 2 modules. The app lets Powerwall owners monitor their home energy system from afar, while also allowing input such as setting a minimum energy reserve in case of a grid outage. "It's really good that you can see what’s happening any time," Brendan said. "And I will check it multiple times a day."

Image: Supplied

While solar panels alone can provide some offset on a household's electricity bill by selling back to the grid in times of excess, Australian feed-in tariffs are disappointingly low. With the end of government incentives such as NSW's Solar Bonus Scheme or the Queensland scheme that awarded a premium tariff of 44c/kWh, solar owners are being paid pennies for their excess power. Brendan is getting only 5.5c/kWh from the energy he feeds back into the grid, though it's set to rise to 11.3c from July 1st.

With feed-in tariffs now four or five times less than the cost of electricity households purchase back from the grid, batteries like the Powerwall 2 are vital to making the most of home solar power. One of the early adopters of the original Powerwall battery, Nick Pfitzner, shared his story with us earlier this year. With the help of his rooftop solar and integrated Powerwall, Nick managed to cut his electricity bill by a staggering 92.2 per cent.

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Nick also integrated his battery with Reposit Power's GridCredits system — whereby energy stored in your battery is sold to the grid during price spikes driven by peak demand, at prices of up to $1/kWh. The earnings from these peak events are given back to Reposit customers as 'GridCredits', which provide a discount off their electricity bill. Brendan hasn't included any extras like this yet, but says that he is "currently looking at Reposit Power as a possibility."

With the fully installed cost of Brendan's Powerwall 2 sitting at $10,917, Brendan is confident in his investment. "The payback time I have calculated is around 7 years," he told Gizmodo. "But as energy prices rise this may lessen."

For Brendan, however, the incentive isn't just financial. As much as he wants to save money, he's also a supporter of Tesla's sustainable energy mission. "My motivation is to get my electricity bill as close to $0 as possible, and for the good of the environment, which is why I chose Powerwall."