Tesla Powerwall: A Battery For Your Home

Tesla has just made a very exciting announcement. It's now using its clean energy nous not only to make some of the world's best electric cars, but also to power your home.

Tesla Energy wants the world to be cleaner, and it's doing so by letting homes, businesses and power companies store their electricity better and reduce peak load on the grid. Here's the best part — we'll get the battery in Australia too, at an incredibly cheap price. It's called Powerwall.

Homes: The Tesla Energy Powerwall

The Powerwall is Tesla Energy's battery for homes. It's available in two sizes — 7kWh and 10kWh, for either $3000 or $3500 US dollars to installers — and is basically an oversized uninterruptable power supply. That price is awesome, and should make the batteries affordable even after installers add their fees and overheads.

Those prices are amazing, by the way. They mean Tesla is able to produce batteries for around $250/kWh, where competitors that are already in Australia cost $1000/kWh. This will be (and I don't use this word freely) a gamechanger for energy storage in Australia once they are available. At the moment, information on Australian integrators is light on the ground, although Canberra-based Reposit Power has apparently teamed up with Tesla to bring the Powerwall to Australia.

The Powerwall has two key purposes and one complementary benefit. It'll connect to both the existing power grid and your solar panel setup if you have one, either storing the energy your solar panels receive for later use or charging itself from the energy grid in times of cheapest off-peak power (for most users, that's overnight). It'll also provide backup power in the case of an outage.

That way, the Powerwall provides a baseline of power to your house during times of peak power cost, but will either provide that power effectively for free (off solar) or at the cheapest possible grid rate (by charging off-peak). The Powerwall battery is rated to 2kW of continuous power and 3kW of peak electricity draw — enough to handle the basic needs of a small household's appliances, lighting and devices.

The Powerwall comes in a bunch of colours, and is designed to be placed on your wall and be visible rather than hidden away. You can stack the batteries, too — anything from one to two to up to nine Powerwalls can be stacked for up to 90kWh of energy storage (at US$3500 a pop). US residents can order the Powerwall now, with shipping in three to four months. Batteries will initially be produced in Tesla's Fremont factory in California and then production will move to the Gigafactory next year.

The Powerwall isn't going to reduce your household's grid energy usage to zero — it's not a big enough battery and would also require significant investment in solar to charge completely — but it will reduce peaks in grid electricity reliance, letting Powerwall users charge overnight instead of in the day time when everyone else is using the network and increasing demand.

And because of that shifting of load, it will reduce the world's need for peak power generation, theoretically reducing the need for dirty power sources like fossil fuels. Australia relies heavily on comparatively dirty coal and gas power generation for baseline and peak power demand, although investment in solar, wind, wave and geothermal energy is increasing — it's Tesla's goal to allow these to contribute more and therefore make things cleaner.

Tesla has confirmed to Gizmodo that the Powerwall will begin sales and installation in Australia in the first quarter of next year, although prices are still to be confirmed. Providers of the technology will be confirmed closer to that launch date.

Powerwall specs:

  • Mounting: Wall Mounted Indoor/Outdoor
  • Inverter: Pairs with growing list of inverters
  • Energy: 7kWh or 10kWh
  • Continuous Power: 2kW
  • Peak Power: 3kW
  • Round Trip Efficiency: >92 per cent
  • Operating Temperature Range: -20C (-4F) to 43C (110F)
  • Warranty: 10 or 20 years
  • Dimensions: H: 1300mm W: 860mm D:180mm

Tesla Energy For Businesses

Beyond the home Powerwall battery, Tesla Energy also wants to supply larger cells to business users — as the Powerpack. Based on the full-size batteries of the Tesla Model S and Model X, said cells will be able to handle significantly more peak and continuous demand by larger users and will last longer while doing so.

There's no word on when and how this will come to Australia, but Tesla is actually already partnering with some pretty big operations in the United States with commercial battery storage and backup systems. Amazon and Target are the two biggest names; Amazon Web Services is pioneering a 4.8 megawatt-hour pilot of Tesla battery systems for its western US data centre region, and Target will install batteries in some of its stores to test its potential.

Tesla actually ran its Powerwall and Powerpack intro event from a Powerwall setup, which drew its power from a set of solar cells on the building's roof — no extra energy required from the grid.

Here's what Tesla has to say:

Based on the powertrain architecture and components of Tesla electric vehicles, Tesla energy storage systems deliver broad application compatibility and streamlined installation by integrating batteries, power electronics, thermal management and controls into a turn key system. 
Tesla’s energy storage allows businesses to capture the full potential of their facility’s solar arrays by storing excess generation for later use and delivering solar power at all times. Business Storage anticipates and discharges stored power during a facility’s times of highest usage, reducing the demand charge component of the energy energy bills. Energy storage for business is designed to:   

  • Maximize consumption of on-site clean power
  • Avoid peak demand charges
  • Buy electricity when it’s cheapest
  • Get paid by utility or intermediate service providers for participating in grid services
  • Back up critical business operations in the event of a power outage

Comments

    this is great. id love to see an australian price point and capacity.

      We'll let you know prices as soon as we find out! Capacities will almost certainly be the same -- 7 and 10kWh.

        is there a comparison in Ah? (im a bit old school)

          Assuming you're running everything off at 240V, 7kWh = 29Ah, and 10kWh = 41.6Ah

          https://www.wolframalpha.com/input/?i=10kWh+in+amp+hours

          "kW h (kilowatt hours) and A h (ampere hours) are not compatible."

            Poccari's answer is completely acceptable. A system drawing 1 amp at 240V for 29 hours uses the equivalent of 7kWh of power for example. They are not directly comparable as they use different units but they are both can be used as a measure of the available capacity of a battery system in terms of it's ability to provide energy for a certain amount of time for a given voltage and current draw.

              You don't need to know current draw. You need to know only voltage, but using Ah to discuss energy is just silly.

              It's like discussing volume in m2, and just assuming a standard third dimension.

                What an utterly useless post. All he asked for was a conversion, not a hypothesis to support it.

                  Not quite as useless as your post though.

                  And I wasn't talking to skinja, I was talking to steve. Perhaps you replied to the wrong person.

      Australian price, $9,999.95 for 7kwh :) ex Aus tax

        Aus tax + subsidies to keep our local electricity companies who won't move with the times afloat.

          My first thought exactly. This or electricity companies will whinge and try to crush it. As the electric car phenomenon so long ago.

      $3500 US translates to roughly $45,000,000,000,000,000,000,000,083.99 AUS.

        You forgot to add the 10% GST.

      I think is will cost around $3600-$4000 AUD plus installation for the 7kw version and around $5000 AUD for the 10kw system plus installation.

      This device will take 38 years to pay for itself at US prices, if you add the Solar Panels another 3500 US dollar option it will only take 31 years again at US Dollars to pay for itself. The Warranty is only good for 10 years and who knows how long the battery will charge after 10 years. As PT Barnum said there is a sucker born every minute, Until the price gets way more affordable it will never pay to install this system,

    Effectively a water tank for your electricity. Such a good idea and so simple.

      Get big tanks, mount high and put a turbine at the bottom - Hydro Electricity.
      Power while you shower :-)

    This looks great and almost a no-brainer for those with solar panels.

    How are power companies likely to feel about this? If it reduces the amount of the more expensive peak power will it eat into profits, or is the cost of producing peak power mean that they their profit is less than on off-peak?

      One the growing problems with solar is the effect it has on the power grid i.e. excess power that needs to be put somewhere, stability issues etc. This will assist in reducing some of those problems.

      With coal/gas power plants, they've got to run them all the time. You can't just turn them off for the night (though you can reduce output), so one of the reasons why it's so cheap at night is because they can't stop making the electricity. So they have to give it away cheap. So I'd say it's definitely going to eat into profits. Not that solar isn't already as the companies still have to maintain the power grid to allow for us consumers (who are getting paid for our solar energy going into the grid) to use it for ever reducing returns.

      Thinking about it, this could actually lead to an increase in off peak electricity usage overall. As people are going to be using it more consistently to charge their batteries.

        Correct but you'll find the rules and regulations of the industry will prohibit charging these batteries with off peak power from the grid and then using that power at peak times replacing grid power - if still connected.

          Have you got a reference/link to that? It seems like if that's true (can't store off-peak power for use later) then these would be worthless to anyone who doesn't have solar panels.

          You'd have to be able to prove that though, which is easier said than done. By that standard, you could get in trouble for charging your car in the evening because you can harness the power in it like a battery. Though additions to the smart grid (specifically in Melbourne, for now) mean they can reduce the amount of electricity that you're using in peak times, they would need to legislate to stop you doing that (which will probably lead to that party being voted out the next election). They can't stop people using power that you're paying to use.

          Is that just speculation, or do you have evidence for that?

          It benefits everyone if the peaks are smoothed out, so there is no reason they'd prohibit it.

          If there is significant uptake, you could expect off-peak rates to rise, and the off-peak times to change. Ultimately, if peak demand is effectively smoothed out efficiently, there may be no need to offer off-peak rates any more. Afterall - off-peak rates are simply a price signal to consumers to shift time of power usage, including encouraging consumers to invest in technology to support this (traditionally off-peak water heaters).

          Likely we'll eventually use spot pricing (eg prices updated 1/2hourly). Rather than having pre-determined peak and off-peak times, the rate will float. Electricity will become more expensive, for example, mid-afternoon on a scorching hot day when everyone turns on their air-con. That's when having local storage will really pay dividends.

      I imagine they would be pretty positive; the issue with peak power is that it puts a huge load on the network and it's mostly businesses. And to cater for that, they have to constantly upgrade infrastructure (which costs $fuckloads), even though the infrastructure is unnecessary the other 16 hours of the day. If this helps cut peak-period demand from households, they still sell the same amount of power but they don't need to raise/expend as much capital.

      It's pretty win-win.

        the infrastructure isn't just unnecessary for 16 hours a day, its unnecessary for the 362 days of the year that the temperature isn't above 42 degrees!

      It'll probably bite us in he arse making the off peak power more expensive to make up for lost profits.. Someone has to absorb the high cost of fixing and maintaining the power grid (which in Australia is massive per capita) and i sure as hell can bet it won't be the government.

      Am i the only person worried about what might happen if everyone started jumping on this and the power companies couldn't afford to run.. don't get me wrong, i love the idea and what it means for the environment etc but i love my power being there in abundance, when i want it and not have to worry about weather i have enough battery to watch game of thrones :)

      Would be good for farm houses and staying off the grid and what not though.

        Well that's just it. If this does work how people here are imagining it, off-peak prices will go up but peak prices will go down too. It's really just taking a volatile and variable market and making it a bit more stable. Nothing lost; nothing gained. As other people have commented though, network businesses have to build for a peak demand not a normal demand, so if this works and there are less peaks, less building, less cost. As far as forgone profits for these businesses, the government heavily regulates them so they always get a normal profit (in theory). Not to get into the nitty gritty of it but under our current regulatory system, network businesses actually get temporarily rewarded with more profit when costs are reduced. The people who loose out here are the ones which own peaking generators but as long as there is some other generator willing to provide, then it shouldn't have an effect on prices.

      Network companies aren't a fan. Due to the massive increase in high-power air conditioners in the 2000s, and the fact that the networks have to be built for peak demand (which is in summer when all those air conditioners are running), they spent a lot of money upgrading their networks 10 years ago, and of course increased their prices to boot. Unfortunately in the last 2-3 years ago there was sudden upsurge in solar panels as well - which, of course, naturally generate the most at the same time as all the air con units are running.
      So the rates have gone up but people are using less... the companies still need to pay for their network upgrades. So they have to up the rates more.. which drives more people to solar... and so on.

      Last edited 02/05/15 10:09 am

        They could also raise service costs like they did with home phones (service costs end up higher than phone call costs), so if the power lines pass your house (which it does for every house) then you will have to pay whether you make your own electricity or not.
        This way they can make extra money and honestly say they haven't raised the cost of electricity. Like you said, the power companies won't like this one bit but they will find a way to keep making more and more money every year.

        Network companies should be a fan. What most people don't know is how the regulatory system works for them. When they charge more, they do not get more profit. The meticulous process of regulators analyzing costs and allowing certain rates works on the basis that they get a constant profit; the only thing that changes are costs. The exception to this rule is when they out-perform their cost allowances. When this happens, the benefit is split between customers and the business (until a new access arrangement is made) as a way of rewarding the business with extra profits. Reducing demand peaks (and infrastructure needed to service peaks) will reduce costs and increase profits.

      That' scan easy one, they just move the peak time!! At our local pool they charge the swim club peak rates because the demand for the pool is highest when the swim club members all turn up!! That' show they justify the charge. Mind you if the swim club cancels training, there is barely anyone there.... Same idea, but power usage times.

    Prettier than existing solutions but like those will almost certainly invalidate your feed-in rebate if you have one. Also, expect at least 50% Australia tax so $6k plus for the 10kwH

      Would love to understand where the "at least 50%" figure is coming from.

    We have solar, so I would love to set one of these up at home. One big question though, is the recharge life of the batteries?

      It has a 10 year warranty. On their website there is the option to extend that for another 10 years. I am taking a guess that the recharge life before major issues are noticeable is 10 years with reasonable ability after that.

    Will likely be banned for sale in Australia but the government. They wouldn't want their fossil energy producing mates to lose any money.

      Yeah exactly - remember, "coal is the fuel of the future" or whatever piece of utter b*llsh*t good old Tone uttered the other week. Stupid idiots won't even admit climate change exists, they're not going to let us buy something that threatens the existing fossil fuel and electricity provider oligipoly.

      Just like with Uber and the taxi industry, you can bet they'll pander to industry demands ! Meanwhile our mates in NZ will snap it up, coz NZ is the Canada to our America ...

        Get a grip.

          Get a grip ? Dude, it's a *confirmed* fact Abbott is pro-coal industry - that 'future energy' remark was widely quoted and commented on in the mainstream press. The fact that Uber is facing lots of legal challenges in this country is also a *confirmed* one. So I'm pretty sure my comments are grounded in reality. Remember we live in a nanny state - plenty of f*ckwits in Canberra and our State + local council legislatures who all think they know what's 'best' for the rest of us.

      Lol, don't be ridiculous, they'd have no grounds whatsoever, legally or otherwise.

      Keep wearing the tinfoil hats guys ... they suit you.

        Tinfoil hats ? Really ? So you're saying the Federal government we have is not anti-science and doesn't contain climate change deniers ? Are we living in parallel universes perhaps ?

        As for legal grounds, you realise they're the mob who MAKE the laws, don't you ? So even if they don't have the laws now, they can create legal grounds to suit themselves.

        Last edited 03/05/15 8:28 am

          There has been no statistically significant warming for 18 years. Even the IPCC admits that. The only 'deniers' are the Warmy Catastrophists who are seeing their 'industry' evaporating.

            There's always one, isn't there ? So you reckon the 'unprecedented' weather patterns we've seen globally in the last few years (and locally in Sydney just last week) are totally 'normal', right ? 25km ice sheet breaking off the Arctic (or is Antartic) shelf that NASA is tracking is totally cool (pun intended) too, huh ?

          The governments stance on climate change really has zero to do on the installation of a battery in someones home. I'm sure there's homes out there right now with some form of power storage, it just so happens that this products quite consumer friendly and cost effective as opposed to whats been available so far. That and so far as brands go, Telsa's right up there in the 'cool' books.

    well thats the worlds lithium reserves depleted in a few years then. how very green.

      Um. Watch this: http://www.bloomberg.com/news/videos/b/3abb52e4-ea59-4ed9-8525-80e5765c701c

      And if we're talking about lithium being used in a recyclable battery versus coal being dumped into the atmosphere, I think I know which I prefer.

    Be interesting to see the Math behind how long it would take to make back that initial cost of battery + installation.

    From my understanding on a 2KW Solar in your average house, it takes years to recoup that cost back before it starts paying itself off. This could pay things off a lot quicker at 7KW of available power.

    Last edited 01/05/15 2:55 pm

      But you're still paying for the electricity, so local prices would also need to be taken into account.

      Using really simple maths and not taking into consideration inflation etc etc.

      In Perth typical consumption per year for a house with 4 people is approx. 7,500 kWh. Cost per unit is 25 c. Therefore total cost of electricity per year is 7500*25/100 = $1,875.00.

      Total cost of the system is Battery ($3,500) + Solar Panels ($6,000) = $9,500.

      Solar / Cost per year = 5 years.

      This is a simplistic view of this and in all likelihood the time before full costs are recovered would be greater

        So buying 1 battery 10Kwh which you will discharge at 2kwh for 5 hours if you run it empty, lets just say that was possible (which of course its not since you should only discharge your battery to about 50% otherwise you will shorten its cycle life) now lets say you have a 2 small AC units each using about 1Kwh at night and you go to bed at 10pm what do you think you will be left with by 3am ? you will be scrambling for the light switch which wont even turn on your lights by then ! or of course you could invest in another battery and have AC until 8am. Either way the point is its still too expensive. and oh I forgot to mention mummy and daddy need to share a bed and the 2 kids be in 1 bedroom !

          But there's a 10 year warranty, so what if you shorten the life cycle, you'll just get another one if it's faulty!

          You can "stack" the PowerWall so you have as much capacity as you need (up to 90kw/h or 9 units connected) and the corresponding increase in possible amps available.

          This system makes sense in a lot of ways. One, it stops peak power consumption for non-solar houses by charging up at night on off-peak rates and drawing down during the peak of the day. It also makes sense for solar powered houses (like mine) because as of December 2016 all the feed in tariffs go away and any excess power generated is essentially not benefiting you directly. With the PowerWall (or any of the current battery systems), you charge the batteries off excess solar power and draw down on it at night.

          Honestly the real trick with these systems is intelligent charge/use control which needs to be aware of both your living habits and the weather. But this is where companies like Tesla excel, so that's why their solution is better.

      It depends on your consumption and usage patterns.

      We averaged $650.00 a quarter for power and installed enough for our daytime usage by solar for about $4,000.00

      Now we are paying about $100 a quarter? Worth it....with these batteries we can nearly go off grid!

      For me, dodgy envelope math...
      peak = 51c/kwh
      opeak = 11c/kwh

      So, in theory, I save 40c for every kwh I switch from peak to offpeak. Assuming this costs, $5k, that's around 12,500kwh.

      We use around 24 kwh/d. Making the generous assumptions that a third of that is peak and gets 100% switched, that's 8kwh a day... or about four and a quarter years to breakeven.

      That's exagerated in my case, because I have stupid TOU metering. The difference between peak/offpeak prices is a lot narrower if you are on a different metering scheme.

      Last edited 01/05/15 3:36 pm

    Needed the home battery swapping station as well. 85Kwa in the floor and one in the car.
    Now powerball come to the party!

      Now powerball come to the party!

      Not sure if.. auto correct fail...or satire. I'm going with the later because it actually makes more sense!!

        No I'm serious when I win powerball, it's 2 Tesla Model S in the house and a home battery swapping station. Solar panels on the roof, recharging one battery pack and powering the house. 85Kwa battery pack will run my house for 1wk with no sun shine and any excess going to the pitiful $0.06Kw feedin Tarif.

    Presumably it uses no rare earth materials?...

      Very good question. Reportedly no rare earth minerals used in the Model S' battery and inverter, so it stands to reason that there wouldn't be any in the Powerwall. But it's possible.

        Come on Campbell you should have pick that. When I win Powerball.

    Tesla is simply doing so much awesome, these days.
    I love this company.
    I wonder if the patents for this are free, like their electric cars?

      I often wonder why more people aren't watching Tesla with the fervour usually reserved for Apple fanboys.

      About a week ago I realised I said out loud "oh, it's nearly April 30 - Tesla are announcing a new product soon." But then, because it was actually likely to be a game changer for a real-world problem, I wasn't embarrassed.

      Apparently the patents will be FREE. " Musk said that the Nevada facility is just "Gigafactory 1," and that there will need to be many other companies building Gigafactory-class production facilities to actually shift the world to renewable energy. To encourage this, Tesla's policy of open patents will continue with the Gigafactory and batteries."

    Been reading more about this. Apparently the 7 kwH is for regular cycling and the 10k kwH is for more infrequent cycling (backup). Hence the pricing being similar.

    Also note that the prices are to installers, not to the consumer. Most importantly though, it excludes the inverter and with an operating voltage of ~400V you aren't going to be able to grab any old piece of garbage off eBay. I'll hold my enthusiasm until I see the full system pricing.

    What power companys in australia have a variable price (on and off peek costs)??

      I believe most have the option. In WA, Synergy call it Smartpower.

    These batteries are not cheap. Quite the opposite, they will cost you roughly twice a much as a lead-acid battery set-up would. Li-Ion batteries are worthwhile where portability and size are important but of your home, lead-acid makes far more sense. A properly maintained deep cycle battery can last 20 years or more, where these things will be down to half their original capacity in half that time. You'd have to have rocks in your head to choose this over lead-acid.

      even deep cycle lead acid batteries don't like being discharged below 50%. especially if you want 20 years out of them. whereas lithium batteries can handle being drained better so effectively you need almost twice the capacity of lead acid to lithium for the same usable power storage.

        Similarly, if you want your Li-Ion batteries to last, you should not charge them above 80% or let them discharge below 20%, leaving an effective 60% range. Then there is the fact that no matter what you do, Li-Ion batteries lose storage capacity over time, whereas lead-acid batteries maintain 100% capacity throughout. In any case, you're probably not going to use much of your store on an average day anyway. With my two 6V golf-cart batteries, I can get 4 or 5 days of normal usage on my yacht (where I live), running my fridge, lights, 32" TV, phone charger, etc. A bank of 8 would provide similar coverage for a house, I'd imagine, so on a daily basis you're probably only looking at 20-25% drain on your storage capacity. And modern solar panels can provide some charge in moonlight so you are nearly always getting something back into the batteries.

          It doesn't matter if they discharge capacity over time, 10 year warranty, it'll get replaced!! Plus, this is all about being environmentally friendly too. Not really very possible with the production of Lead acid batteries.

      Nonsense. As noted in this article prices in Australia are about four to five times this for the same storage capacity. I knew this product was coming but the price surprised me. Even if Australia tax doubles the price it will still be about 40% of current batteries here and with better life span.

        How will it have better life span? Li-Ion batteries lose capacity at a steady rate throughout their lifetime. e.g. My 2009 Dell laptop now lasts less than half as long on a charge as it did when I bought it. Lead-acid batteries have consistent performance throughout their lifetime. The Trojan T105s I use offer you 1.5kWhr for around $200 (bought in bulk). So to get to the 10kWhr Tesla are offering for US$3500, around Au$4900 (with GST), you're looking at 6 or 8 batteries, which is only going to cost between Au$1400 and Au$1800. So it is one-third of the cost for a longer lasting set-up.

          These are not identical technology as in a lap top or no-one would want them and they would not be powering electric cars for years on end. You're doing well to get half the life out of your 2009 battery for Dell, the battery for my newer laptop has died completely. Unlike your laptop battery they come with a ten year warranty. Lucky to get one year with a battery for laptop. If you can beat the Tesla batteries for cost and reliability in six years when my feed-in deal comes to an end we'll talk :)

          Correct me if I'm wrong but the T105s come with a two year warranty so best case scenario if they survive 10 years they will cost me about half the price of the Tesla batteries, worst case if I have to replace every two years then it will cost me two or three times as much.

      These batteries are not cheap. Quite the opposite, they will cost you roughly twice a much as a lead-acid battery set-up would.

      Complete rubbish do your research first then comment !

      http://www.powertechsystems.eu/en/technics/lithium-ion-vs-lead-acid-cost-analysis/

    I'm just waiting for the time when every house in the developed world has one of these installed, then Elon Musk pushes the red button which transforms them into world dominating drones. Evil villain complete haha.

    I wonder if I could get multiple of these? Could use 2 or 3 on different fuses in different configurations. Also dont want the washer and dryer on these.

    Unless we get price gouged like Australia always seems to on things... Will be very interested to see what the price ends up being for us.

    Thanks for the write up Campbell. Don't forget that you will need to add a battery inverter with a sophisticated control system if you want to use this safely in your home. Add that to the price and get it installed and my guess is that you'll spend about $10k all up. But that is still about half the price of a conventional battery storage system + battery inverter and controls fully installed.

    And Reposit Power are not bringing the Powerwall in - they are actually installing their software on the Powerwall compatible inverters to allow direct trading on the wholesale market. But the hardware will be brought in by other people. Reposit are a software company. The value of this to the owner will be from $300 to $1000 per year in extra income. Pretty cool for uploading some software to existing hardware.

    More details here:
    http://www.solarquotes.com.au/blog/will-the-tesla-powerwall-let-you-go-off-grid-for-3500/

    how many in a row do you need to power the oven, cooktop, a/c, kettle, TV, a few lights and your fridge all at the same time? I thought the specs said 2kw, that might do 1 high current appliance.

      Peak output is 3 kw. You must be running some pretty high current stuff to need more than a 6 kW draw (two units). My induction cooker and clothes dryer (which barely gets used) are about the only things in my house that tops 2 kw, But even then the system will be smart enough to draw from the grid when it needs to compensate or panels if you are cooking during the day. We are a high electricity use household but even in winter with the panels we don't currently use more than 22kwH of electricity from the grid per day and have 9 kwH spare to feed in. In summer we generate almost twice the excess than we draw back in. I reckon three of the 7kwH for daily cycle and one 10kwH for backup would cover most contingencies but we'd still need the grid for a few months of the year to compensate for the fact we could only store 9kwH per day and drawing 22kwH. And in six years time when my feed-in runs out the battery price should be pretty reasonable. I also expect Tesla will encourage providers to sell these batteries on a Solar City model where you pay so much up front and then so much per month for five or ten years.

      Last edited 01/05/15 8:40 pm

    I don't think the power companies would want people to save up off peak electricity to use during on peak times. They don't like losing money and have already pumped up the price of electricity for the people with solar panels. They're not stupid and they expect ever growing profits. If a large number of people but this, the power companies will just raise service cost and that means you will be paying them money just because the power lines run past your house. The same thing happened with home phones. The service cost is often higher than the actual cost of the calls.
    All in all, it sounds great but because of government protectionism, were all going to be paying more in the end.

      If you live in regional Qld - it's not protectionism - it's called a government subsidy to about $800 per year per house/business to make sure tariffs are uniform and affordable. And thank goodness!

        Hey, that's pretty good. 800 dollars is more than I spend on electricity each year. Would that mean I would get my power for free?

      I don't think this is a thing of protectionism. Also, I don't think power companies are going to worry. When you say a thing like 'power company', you cold be referring to retailers, distributers, transmission businesses or generators. Fortunately, distribution and transmission businesses (which form the majority of your bill) serve to gain from this. Efficient battery use means less peak demand and less infrastructure they have to build (less cost, more profit). Retailers will likely just changes their tariff structure to suit the market (flat tariff instead of peak/off-peak) and derive the same rate of profit from customers. The ones poised to loose from this are expensive to run peaking generators. The fortunate thing is that if peaking generators are not run then they are simply not paid. Declining demand, solar and (eventually) this battery technology, all exert a downward force on prices.

      Last edited 03/05/15 4:14 pm

    Top end of that temperature range a bit low for Aussie conditions. Definitely need to install inside. If that's its biggest problem though? Bring it on.

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