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Powerwall 2: Tesla doubles up on battery storage and slashes costs

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One Step Off The Grid

Just nine months after the first batch of Tesla’s 7kWh Powerwall battery storage systems hit the Australian market, the US company has unveiled the Powerwall 2 – a smaller, sleeker second generation unit with double the energy storage capacity at nearly half the cost per kilowatt hour of its predecessor.

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The new and improved 14kWh Powerwall 2 was launched on Friday night in Los Angeles alongside Tesla’s solar roofing product – a shared BIPV vision with SolarCity whose rollout rides on the success of the two companies’ planned merger.

The company also used the event to launch its latest model EV charger and a second generation commercial/industrial battery unit, the Powerpack 2.

But it was the Powerwall 2 that made the biggest splash, largely due to its doubling up of capacity and halving of costs (in terms of the price per kWh), all of which have offered a glimpse at the break-neck speed at which this game-changing technology could be evolving.

Indeed, in a Q&A following the launch, Tesla CEO Elon Musk said his company “expects to sell more Powerwalls than cars,” owing to potential demand for the product in parts of the world where power isn’t reliable or even accessible – or is very expensive, as in Australia.

On cost, according to the Tesla website, the price per unit in Australia will be $A8,000* (with GST), or just under $10,000 fully installed. According to one accredited Tesla reseller and installer, the cost of a solar an storage system, featuring 3kW of PV and one Powerwall 2, would be around $16,500.Powerwall-2-Transparent-611x923

And the specs? While the battery’s lithium-ion chemistry remains the same, the biggest change to the battery’s hardware is that it now incorporates an inverter – Tesla’s own product – which answers one of the previous model’s biggest criticisms, and goes to cutting the cost and complexity of install.

On performance, the battery’s “round trip” efficiency is listed as 90 per cent, while its peak power rating is 7kW and 5kW continuous. According to the Tesla website, one battery pack could power an average two bedroom home for an entire day, or could get a four bedroom home through an entire night, meaning that some solar homes would have the potential to cut their grid power dependence to next to nothing.

And, like its predecessor, the Powerwall 2 can also provide back-up if the electricity grid goes down.

The appearance has changed, too. At 45.3 x 29.7 x 6.1-inches, the new rectangular unit is around 40 per cent smaller than its predecessor, but weighs in at a hefty 122kg. It can be installed inside or out, and can be wall or ground mounted. It is also stackable.

As for when we will see the units in Australia, that won’t be until sometime in Q1, 2017. But according to Natural Solar CEO Chris Williams – who just returned from attending the “very exciting”  launch event in LA – demand for the new generation Powerwall is already far surpassing levels seen for the 7kWh model.

“This time the response has been maybe double or triple the response for the Powerwall 1,” Williams told One Step Off The Grid in an interview on Monday.

Powerwall-2-Dimensions“The really exciting prospect here is double the battery at lower cost per kWh, lower installation rates, so the value is going be better.

“Cost per kWh 15 per cent more than the current package, but the value that you’re getting is 100% more.

And the timing for the capacity increase looks to be spot on, despite some analysts arguing that the best value for homeowners now is in much smaller battery units.

Williams says that when the first Powerwall hit the Australian market, 95 per cent of orders his company received were for one 7kWh unit. Within just a few months, however, Williams saw that “dramatically adjust”, with many people ordering two units, to better meet their energy needs.

“The reduction per kWh of solar and of batteries is on a great trajectory,” Williams said. “There is a lot of satisfaction, for us, in being partnered with a company that is leading the way with innovation.

“Where the market is today, compared to where I thought it would be; I think we’re five or six years ahead,” he said.

Meanwhile, the original Powerwall, which made its rockstar debut not even a year ago, looks to have been consigned to the dustbin of battery storage history. Natural Solar’s Williams says his company will continue to install the 7kWh units it has in stock, but will be focusing solely on the Powerwall 2 going forward.

“This is the future for energy management – where control goes back to individual households enabling the homeowner to visibly see and control their energy usage – helping Australian families increase their independence from the grid and save thousands on their annual energy bill,” said Anthony Tannous, Tannous, the executive general manager of CSR Bradford, another accredited Australian Tesla reseller/installer.

“A typical Australian household consumes 21 kilowatt hours (kWh) per day. The Bradford Solar ChargePack including Tesla Powerwall 2.0 is capable of storing enough power to cover an average home’s evening energy usage – helping a family of four save up to $1,500 on their annual energy bill.”

*An earlier version of this article said the Powerwall 2 would retail at $8,800. The correct price is $8,000.

This article was originally published on RE sister site, One Step Off The Grid. To sign up for the weekly newsletter, click here.  

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  • Brunel

    Why are you using inches instead of cm or mm.

    • MaxG

      Lazy, Cut and Paste from somewhere — or not realising AU signed up from metrication in 1975, decimal day in 1966 I believe.

      • Brunel

        But now a lot of Aussie journalists, including on the ABC, say “June 24, 2017”!

        Our power bills say “24 June 2015”.

        British newspapers print “24 June 2017”.

        My Aussie passport is issued on “22 May 2010”

        Strange and unfortunate that Fairfax newspapers print it the American way.

  • john

    I have put together a small program to work out how the ROI would be on this now with a new install i estimate it would take maximum of 30 minutes to terminate 6 wires yes i know they work slowly at $100 an hour.
    On cost, according to the Tesla website, the price per unit in Australia will be $A8,800 (with GST)
    Even with this the ROI is very compelling down to 67% DoD over 10 years you are in front with cost of energy @ $0.25 per kWh.
    Roll on the installation of battery backup i would imagine.

    • nakedChimp

      I’d really like to see a teardown of one. 🙂

  • Steve

    Tesla states that this is good for off grid also. https://uploads.disquscdn.com/images/52156a41e6e1eb5b3024b597c3e88da9b298716564f63402f801d1637c5aff9b.png

    Does it include an MPPT charge controller, PV input? What is the max input from a PV array this will accept?

    • nakedChimp

      I’m pretty sure it works via 120/230VAC .. so you would need an inverter (probably a special one, definitive something like a hybrid one that can be set to not export to the grid or something).

      • Steve

        I need a charge controller. Off-grid you need to go from PV to the charge controller and charge the batteries. The inverter that’s buit in will provide my output of 120/230VAC .
        It already has an inverter integrated:
        Rated: Power 7kW peak / 5kW continuous

        • nakedChimp

          As I said (in some post on that ABB hybrid inverter article a couple days back) the perfect solution isn’t here with us yet.
          I highly doubt the PW2 is made for pure off-grid applications, for this the unit would need to include (as your pic shows) an input for solar pv with a charger that is made for it.
          The unit probably has got a charger that can convert from 120/230VAC to battery and back, but not directly from PV (depending on system design anything from 50-600VDC input).
          Maybe it can control certain PV inverters to control their output when the grid is not available as sink and they need to just feed the PW2+loads in the house?
          SMA does it that way.. just a couple of boxes and a lot of money needed.

          For smaller loads you can also look at Chinese based hybrid inverters which have everything to go completely off-grid if needed (batteries are then a separate unit attached to them usually at 48VDC.. chargers mostly can do LiX and LAB).
          A nice little unit (non stackable) I have seen pretty recently is from a company called Lantrun – Aegis 4000/5000. IP67, no active cooling, unfortunately non-stackable (so 5kW is all you get per load connection on it on the larger model), but can grid-feed or grid-backup if needed and go into island mode from PV/batteries when needed.

          Personally I want a system that can give me 30-60A at 230VAC, so about 14kW on a single phase continuous for an island grid.
          Main feed would be by PV without much conversion losses (so about 400VDC bus internally).
          The grid would permanently be decoupled from the load side of things and only be there as backup feed if needed – so permanent island and no crappy voltage surges or other stuff from the mains grid.
          The batteries would smooth out load vs. supply.

          You can’t buy that yet, but I’m sure it will exist in 3-5 years.

          • Steve

            https://uploads.disquscdn.com/images/52156a41e6e1eb5b3024b597c3e88da9b298716564f63402f801d1637c5aff9b.png
            This is posted on the Tesla Powerwall 2.
            Your path off grid
            “Combine solar and one or more Powerwalls to power your home independently from the utility grid.” Is he lying?” I understand AC coupling and most of the systems they install use microinverters. He claims that you use self-consumption, meaning all your solar DC harvest goes directly to the batteries

            “Use more of your solar Most homes use a fraction of the solar energy they collect. Instead of sending excess solar energy into the grid, Powerwall stores it for use any time.”

          • nakedChimp

            Yeah, I’ve seen it, but without more detailed specs that usually only a manual delivers I’m as wise as you are.

            Current ‘state of the art’ to take a house safely off-grid the system needs a change over switch between your energy mater and your breaker board. And then an inverter that creates it’s own AC net to take over when the main grid fails.

            In my POV all pretty clumsy and geared towards still using the grid as main source/sink for power.

            If you see the grid only as a backup, don’t care for exports that much (big enough batteries, cheap solar panels, etc.) then this whole proposition becomes more or less expensive and you rather just want to tap into the grid IF your own energy sources have a bad streak.
            That’s where I see at least the fringe heading, but I can’t see the device(s) for it yet (permanent islanding with ~14kW continuous rating + battery backup for 2-3 days @10kWh per day). That’s what I described up there.

          • 小杜 (xiao du)

            Quite a lot of the world lives in countries where the grid isn’t stable or reliable. Its not quite as much of a fringe use as you’d imagine.

          • nakedChimp

            Even better, this just means that this solution will appear 100%.

      • Steve

        https://uploads.disquscdn.com/images/da14fc63af21438599683b1880fddb534755bfef2b6828ac3df60c3c6e4316b0.png
        Like this, for my situation. I need to know if PW2 can do 100% true off-grid without hybrid.

      • stucrmnx120fshwf

        Reread the article, it says, that there’s an inverter in the powerwall, so you don’t have to convert to AC, then DC, then AC. You get the juice from the solar in DC, it gets stored in DC (it’s a battery, not a power utility,) then it gets converted to AC, via the inbuilt inverter and you use it. At half the price per kWh, with an inverter thrown in, the electricity companies are about to get a slapping, for cutting the feed in tariff.

        Worse with the tiles, costing less than the cost of tiles, plus solar installation, on newly constructed houses, you’d be stupid, not to go solar and storage, as part of your mortgage. It’s stupid already, not to install solar, on newly created houses, because half of the cost of solar power, is installation. But now with tiles cheaper, storage cheaper, inverter thrown in, you’d have to be out of your mind, not to go solar plus storage, on a newly created house. Given that interest rates are extremely low, it has to be much, much cheaper than utility power costs.

        Because, your barely paying, for the transmission network cost and when you’ve got excess, they pay you at peak prices, for your spare power at night, because of all the excess, daytime solar capacity.

        • nakedChimp

          There is not just one inverter in there (that layman term is wrong anyway, as nothing is being inverted) but at least two converters, probably more.

          Also, you can’t just hook up solar (what array size? = voltage/amperage?) to a battery with charger/discharger.
          The first thing that usually happens is, that the solar energy is being converted via some buck converter into the lower battery bank voltage (= higher current) if you got a direct battery charger.

          For more complete solutions (layman: hybrid solar inverters) that’s not done either, there the solar energy is usually converted (buck/boost) to a system bus DC voltage of about 400VDC (grid tie inverters internally work the same way).
          To that DC bus inside the unit are then connected:
          1) a DC-AC-converter that makes your 120/230VAC load supply
          2) a battery charge/discharge unit that usually is comprised of a dc-dc-(down)converter (=buck converter) and a dc-dc-(up)converter (=boost converter)
          If the hybrid inverter is able to take also energy from the grid (or exchange it with it) then usually the grid is not connected to that 400VDC bus via some converter, but just switched to the load output.

          Now, the PW2 spec website doesn’t state that it can take in solar PV directly. If it does, please point me to it.
          Thus I assume it needs the help of a throttle-able solar grid-tie inverter (units by SMA or Selectronics can do that) that provides only what the battery unit requests for the island.
          Normally grid-tie inverters can’t throttle and just dump everything into the grid – they can’t be used to provide emergency 120/230VAC.. not even with a PW2.

          If the PW2 could take in solar directly it wouldn’t be a battery with charge/discharge controller anymore, but become a hybrid battery containing inverter.
          Would be a whole new category of devices.
          Pretty sure if Tesla would have built that, they would say so.

          PS: and why 400VDC?
          Because it’s pretty convenient to create 230VAC from that with some headroom to spare, that is needed to push energy into the mains grid.

          PPS: data centers with modern DC distribution didn’t chose 380/400VDC by chance.

          • stucrmnx120fshwf

            Maybe they’re getting closer at least, my dip elect comp tech net admin spec, was in net admin, eg. Server 2016, not solar inverters.

  • Aaah, at last! I hope this can retrofit to an existing install. I’m sick of exporting 80% of my electricity to the grid and valued and 7cents per kWh

  • AltEnergy

    I got pretty excited about Elon’s announcement of the Solar Roof so I made this analysis video https://youtu.be/-wlvmzR6dl01