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, building on the success of the original Powerwall that was launched in 2015. One of the biggest changes is the inclusion of a built-in inverter, where the original model required the purchase of a separate one.

The Powerwall 2 almost doubles the capacity of its predecessor, upgrading from 7kWh to a generous 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 theoretically even move off the grid.

This is what Brendan found when he crunched the numbers before 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 explained. "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 big story in the week of the Powerwall 2's launch even called out Tesla's shiny new battery on already being 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 a cost per warranted kWh of at 19c - the lowest all batteries currently on the market. Tesla's Powerwall 2 claims 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 have, the Powerwall 2 is still able to compete closely with the super cheap Australian model. For Brendan, 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 the other key tipping point - with the improved model on the market 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."

The Powerwall 2 has added another little advantage over its predecessor (or even its competitors) with its integration into the Tesla app. While the app was originally designed 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, though input is restricted to small tweaks 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 offset some of a household's electricity bill by selling back to the grid in times of excess, Australian feed-in tariffs have recently dropped too low to provide any real financial incentive. 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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$2,110.46 - that's how much the Pfitzner family says they have saved in power bills since installing a Tesla Powerwall 12 months ago, with the yearly bill for 2016 coming in at $178.71. The Sydney residents, who were the first in the world to install a Powerwall on their home, claim to now pay just 50 cents a day for electricity.

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Nick also integrated his battery with Reposit Power's GridCredits system - where energy stored in your battery is sold to the grid during price spikes driven by peak demand, at premium 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 in his set up 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."

Yet as happy as Brendan is with his investment, the incentive isn't just financial. As much as he wants to save money, he's also a big 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."

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