Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Power Technology

Tesla Announces Home Battery System 514

An anonymous reader writes: Early this morning, Elon Musk finally revealed Tesla's plans for the home: battery systems designed to store up to 10 kWh of power. The company is leveraging the battery technology they've developed for their electric cars to enable more people to switch to renewable power for their homes. There will be two models of the battery. The 10 kWh version will cost $3,500, and the 7 kWh version will cost $3,000. They can deliver power at a continuous rate of 2kW, with peaks up to 3 kW. Crucially, the batteries will be warrantied for 10 years. Musk thinks the market for home batteries will expand to at least two billion, eventually. But even a much smaller uptake for now will validate the creation of Tesla's "gigafactory."

"The gigafactory is the recipient of the largest incentive package ever given by Nevada at $1.3 billion, which followed a hotly contested tax incentive bidding war between various states to land the Tesla battery plant. For the investment to pay off, Tesla needs to convince hundreds of thousands of consumers per year to buy its cars and battery products, with the gigafactory serving as a cornerstone to the company's sales strategy. ... An early gigafactory rendering released by Tesla stated that the plant will have an annual battery pack output of 50 gigawatt hours — the bulk of which will go toward batteries for cars with most of the remainder to be allocated for stationary batteries, according to figures mentioned by Tesla's chief technology JB Straubel last year. The gigafactory's sheer scope makes other battery products a possibility as well."
This discussion has been archived. No new comments can be posted.

Tesla Announces Home Battery System

Comments Filter:
  • Gamechanger (Score:5, Insightful)

    by vakuona ( 788200 ) on Friday May 01, 2015 @08:51AM (#49592435)

    This battery could power a smaller sized home for a whole day. Kind of thing that can make solar energy viable.

    Love him or loather him, but Musk is changing the world.

    • Why would anyone loather him?
    • What would make solar energy viable would be panels that didn't cost $30,000 to buy and install. Much like Tesla cars, solar panels are still mostly toys for the rich. Real people can't just go out and spend $30,000 on panels that may or may not eventually pay themselves off at some point in the distant future (decades from now, assuming they never need any maintenance and your power company let's you piggyback them onto the grid at no extra charge, which are HELLUVA assumptions).

      Don't get me wrong, I would

      • Re:Gamechanger (Score:5, Interesting)

        by Ol Olsoc ( 1175323 ) on Friday May 01, 2015 @10:18AM (#49593099)

        What would make solar energy viable

        2 thousand dollar houses would make homes a lot more viable too.

        I get your argument, I really do, but it's like saying that finishing the living room or kitchen isn't viable because of the cost. You could just staple plastic to the walls, and get cardboard bankers boxes from Staples instead of cabinets and save a lot of money over kitchen cabinets and drywalling.

        Reductio ad absurdum arguments aside, yes, solar and batteries technology is expensive, but it is falling. Coupled with reductions in power needs as we get more efficient lighting and appliances you'll see a lot of the arguments fall like dominos.

        If I might give an example. I concurrently re-insulated my house, and switched from an oil furnace to one of the new super-efficient gas furnaces, which burn so clean and efficiently that the chimney is a PVC pipe and a condensate return to the sewer.

        I now spend for the entire heating season roughly what others in houses my size and in my area are spending a month. If ROI is paramount, I've reached that point after a few years.

        That isn't even taking into account the increases in comfort, less housecleaning because of cleanliness (oil heat is filthy) and reduction of electricity use because the gas furnace blower fans are also engineered for efficiency.

        Finally, yeah, its expensive, but all these advancements are at first. Its started off as people for whom money isn't an object, but are interested in the gee whiz factor. Then as production economy starts to kick in, the costs start to come down, and more and more people start using it. Eventually it becomes the norm.

      • Re:Gamechanger (Score:4, Informative)

        by Jeremi ( 14640 ) on Friday May 01, 2015 @10:31AM (#49593225) Homepage

        What would make solar energy viable would be panels that didn't cost $30,000 to buy and install. [...] I just don't happen to have $30K laying around.

        This game changer has already occurred in many places. There are many locations where you can get a home solar array installed without paying any money for it, because the installing company is willing to pay for the equipment and installation in return for selling you the generated power. This is appealing to consumers because they get a significant reduction in their monthly power bill, they don't have to pay anything, and they don't have to take on the risk of not getting the expected return on their investment.

        The fact that solar companies are willing to take the financial risk on the customer's behalf indicates that the risk/reward ratio of home solar installations is already low enough to be economically viable, and it will only improve over time.

      • So enter into a power purchase agreement, or a lease. Or, take advantage of one of the solar companies offering low interest loan programs.

        The days of having to whack out a 5-figure payment in order to go solar were over like 6 years ago.

      • Re:Gamechanger (Score:5, Interesting)

        by wile_e_wonka ( 934864 ) on Friday May 01, 2015 @10:47AM (#49593345)

        Like the parent post said, "Musk is changing the world":
        Solar City lets you buy your solar panels for zero down and "lets you pay off your loan with monthly payments based on the electricity your system produces." So it ends up that the electric bill plus the Solar City bill add up to less than the old electric bill. You don't need a pile of money lying around to buy a modern home solar system. Non-wealthy people who do not care about the environment are signing up with Solar City simply because they'll pay less for utilities.

        So, yeah, Musk is changing the world--he's causing people who don't care about the environment to put solar panels on their house that a few years ago would have made zero financial sense. In case you haven't noticed, he also made an all electric vehicle drooled over by people who don't care about saving gas.

      • The real issue, is the grid tie in inverters. You'll go through a few of them in the life of the panels, and they are expensive. If they get those down to a couple hundred dollars, the rest will fall in place. Installation and power electronics is over half the installed system cost. This also makes it not financially feasible to buy a couple panels and roll out more as you save money; the price difference between the whole system and the two panel system designed to be upgraded is negligible.
    • Love him or loather him, but Musk is changing the world.

      I really like his after shave/cologne too.

    • That helps someone with solar panels, but more exciting is that it helps everyone - just just people with their own energy sources.

      These shift load on the system - they don't just make solar energy viable, they smooth out load on the power network, and make alternative energy sources that may not be reliable much more viable.

      Not to mention suddenly everyone is much less dependent on reliable power, so it can eventually bring the possibility of reducing the extreme availably requirements of power - you coul

  • by talexb ( 223672 ) on Friday May 01, 2015 @08:54AM (#49592445) Homepage Journal

    Great idea. My power supplier currently has rates based on TOU (Time Of Use - []), and I'd love to be able to charge up the battery supply for my house overnight at cheap rates, then run off the battery the rest of the time.

    I just hope it's not going to be one of those "Only available in the United States" deals.

    • Have you calculated the cost difference in hourly rates, your yearly use and the total price of such a setup? How long will it take to pay itself back before you see any financial gains?

      • by duke_cheetah2003 ( 862933 ) on Friday May 01, 2015 @09:18AM (#49592563) Homepage

        Have you calculated the cost difference in hourly rates, your yearly use and the total price of such a setup? How long will it take to pay itself back before you see any financial gains?

        IMHO, this is totally the wrong way to look at this technology. Personally I don't care if it's more expensive than conventional power, if I could install a small wind turbine and a few solars on my property and charge this battery, it's off the grid for my acre. Totally worth it. People need to stop thinking in terms of 'its more expensive than conventional power.' That is the wrong way to look at this, IMHO.

        • Re: (Score:2, Insightful)

          by Chas ( 5144 )

          People need to stop thinking in terms of 'its more expensive than conventional power.' That is the wrong way to look at this, IMHO.

          No. This is EXACTLY the way people need to look at it.

          Cost vs benefit. If a solution is uneconomical NOW, buying it is a silly splurge, like buying a $100,000 sports car as your daily driver in Alaska when what you need is a $30,000 4x4 truck.
          That, "SOME DAY" it might be more economical to install an identical system does not change the fact that it's still a silly splurge NOW.

          If the system does NOT pay for itself over a reasonable period of time (and within the lifetime of the product warranty), you're s

          • by swb ( 14022 ) on Friday May 01, 2015 @09:43AM (#49592775)

            First, none of these things move forward without some enthusiast buy-in. Loads of things are stupid from a strict dollar-efficiency perspective but people still do them anyway. Computers held fairly low value in terms of dollar efficiency for decades, but enthusiasts found them worthwhile and helped move that industry forward.

            Second, you confuse cost and value. You know the cost of the utility power and the off-grid generation and storage components but you don't know the value to the consumer of being off-grid. What you see as a splurge they may see as some kind of inherent value.

        • by ledow ( 319597 ) on Friday May 01, 2015 @09:55AM (#49592889) Homepage

          However much you hate it, the bottom-line finance number gives you an idea of the materials, work, availability, etc. involved.

          A system that is not economically viable is taking MORE product out of the earth, and rarer products, that need more refinement and processing, etc. in order to create it in the first place than it is replacing other power-generation methods and their costs.

          It's quite simple. The market price changes to reflect the difficult, cost, legislation, rarity, etc. of the materials and labour involved. If something is more expensive it's because it COSTS MORE to give it to you. If something can't pay that cost back (at least, in a reasonable time) you've taken out MORE from the earth including shipping the thing to yourself and paying for machines to modify it, and paying for the companies mass-production plans, etc. than you've stopped being taken out elsewhere.

          It's not perfect. It's not entirely accurate. But the monetary cost of something is a pretty good indicator. This is why lithium batteries are more expensive than lead-acid equivalents, why oil products are being taxed, why discovery of shale gas can drop the gas price, etc.

          Also, as you're moving the burden from government and entire countries to individual users here, cost matters more than most other things. You're asking ME to take the effort, research, purchase, maybe pay for planning and electrical works, etc. this product that you're SELLING in order for me to help the earth. There's a cost involved in that no matter what. Some of that cost is a "donation" because you want to live in a friendly way. Some of that cost is because of the convenience to you if the power blips for a moment. Some of that cost is for your peace of mind.

          At the end of the day, cost is a pretty good measure of all kinds of things to do with a system. This is why energy companies are complaining about the "payback" electricity schemes from solar users... the costs they incur to put their pittance of electricity back into the grid far outweigh anything else. The government has to subsidise those costs, or the electricity companies have to raise their prices. And, suddenly, it's actually more expensive to run "off-grid" than you thought and you end up going back "on-grid" because the cost isn't worth the convenience any more.

          I could UPS all my appliances today. I could just buy a tiny UPS, or save up towards a bigger one, each month and stick them on batteries that survive power outages for whatever length of time I choose to do it for. But I don't because it costs. And that cost does not compare to the cost of the power going off every now and then, or the electricity company raising its prices by 10% a year.

          If an off-grid system does not return money for you, the money you pay would have been better off just buying a generator and some fuel for it for the rare occasions the power does go off, and forgetting about all these fancy gadgets that help you live off-grid. In which case, both the green-ness and the user suffer.

          That's why governments are subsidising PV etc. installs. They have to bring the price down or people will just look and think "Sod it, I'll just buy a genny and keep a tank of petrol in the garage for if anything happens" rather than go off-grid.

          Things have to be profitable, and everything has a cost.

      • by RingDev ( 879105 ) on Friday May 01, 2015 @09:27AM (#49592619) Homepage Journal []

        Up to 17 cents cheaper per KWH (22c day, 5c night).

        Assuming you blow 10kWh per day, primarily between 6am and 11pm, that's upwards of $2.20/day.

        If you move your entire 10kWh load to the battery system and charge it over night, it drops you down to $0.50/day.

        $1.70 savings per day. That's 2058 days to recoup the $3500 expenditure, or just a bit over 5 1/2 years. Over the ten year warranty period you'll save ~$3000, assuming electricity prices remain constant.


      • by mspohr ( 589790 ) on Friday May 01, 2015 @01:46PM (#49595037)

        Where I live, the time of use differential is 14 cents. I could save $1.40 a day with this battery. $511 a year for an investment of $3500... good return.

    • by Nkwe ( 604125 )

      Great idea. My power supplier currently has rates based on TOU (Time Of Use - []), and I'd love to be able to charge up the battery supply for my house overnight at cheap rates, then run off the battery the rest of the time.

      Are your night rates less than half of your day rates? I ask because battery charging isn't 100% efficient. I don't know the charging efficiency of the Tesla packs, but many battery types are only around 50% efficient in charging. By 50% efficient, I mean when charging you put in about twice as much energy as you can take back out later.

    • by Ranbot ( 2648297 )

      ...I'd love to be able to charge up the battery supply for my house overnight at cheap rates, then run off the battery the rest of the time.

      Batteries are not 100% efficient at storing and transmitting their charge, so you might not find much if any savings in your electric bill with overnight charging. If there is savings, then you have factor in how long it will take for that to give you a return on the investment and any long-term maintenance costs.

    • Assuming you get 2,000 cycles out of the battery, at $350/kWh(B) it is $0.175/kWh shifted. Further assuming 80% round-trip efficiency you are at about $0.22/kWh that needs to be saved to pay for the system. Add in a 5% cost of capital and you need your off-peak energy to be $0.25 less than peak period.

      Stated another way, 2,000 cycles is 5.5 years. If you combine a 4kW PV system (roughly $16k) with this, you have an annualized cost of energy of $2,400 (assuming no interest). If you stretch the life to 10

    • And if everyone does that, the cheap rate goes away - its only there because there is excess capacity at that time, and its not worth taking more generators off line during the middle of the night consumption troughs because it takes them time to come back up for the wake-up peaks. Thats the reason the cheap rate exists (we call it Economy 7 in the UK).

      So if everyone avails themselves of the cheap electricity in the middle of the night to store for use during the day, the excess capacity vanishes and instead we get an actual load needing to be catered for in additional capacity. So the cheap rate would be discontinued due to changes in consumption habits.

      • by ranton ( 36917 ) on Friday May 01, 2015 @10:05AM (#49592971)

        So if everyone avails themselves of the cheap electricity in the middle of the night to store for use during the day, the excess capacity vanishes and instead we get an actual load needing to be catered for in additional capacity. So the cheap rate would be discontinued due to changes in consumption habits.

        And when that happens the power companies would need far fewer power plants because peak usage would drop dramatically, perhaps around half what it would be otherwise. This sounds like a great situation.

        Temporary solutions to many problems is all we need as technology continuously improves. Take advantage of Time of Use rates today, and in five years switch to primarily solar power as the prices drop even further. Everything doesn't have to be a fix that will last a lifetime.

  • The consumer version bears a disconcerting resemblance to a coffin for a particularly obese child; but I'm liking the looks of the rack-based unit.

    This might have something to do with a recent spate of obnoxious fights with some of our APC UPSes and their surprisingly touchy and death-prone lead acid battery modules. Even when the UPSes themselves arent' dropping dead, swapping out SLA modules every 2-3 years, at best, gets real old, real fast.
  • unit mismatch (Score:5, Informative)

    by edittard ( 805475 ) on Friday May 01, 2015 @09:02AM (#49592475)

    battery systems designed to store up to 10 kWh of power.

    kW is a unit of power. When you multiply it by a unit of time it becomes a unit of energy.

    • by Twinbee ( 767046 )
      It's almost as if everyone tries to get it purposely wrong. Even tossing a coin would yield a better success rate.

      It's so easy to understand. Just like "their" versus "they're".
  • by Anonymous Coward on Friday May 01, 2015 @09:03AM (#49592477)

    So if you turn on your stove and clothes dryer, your TV shuts off? It's like my college apartment all over again.

  • Prices May Vary (Score:4, Informative)

    by Toad-san ( 64810 ) on Friday May 01, 2015 @09:17AM (#49592557)

    I'm reading the 10 kWh pack may be more like $4500 rather than $3500. I like that 10 year warranty though .. and you get whole-house surge protection of course, I'm sure.

  • by DaChesserCat ( 594136 ) on Friday May 01, 2015 @09:22AM (#49592597) Journal
    Many of the utility companies, such as the ones in Arizona and Hawaii, are griping about people adding solar PV to their homes. These people have, typically, used Net Metering; any power they produce in excess of what they consume at any moment is fed back into the grid and, when their demand exceeds their supply, they draw from the grid. The utility company gets to "reimburse" them for the power they contribute. In some areas (California), 1 kWh contributed during peak hours = > 1 kWh they can withdraw during off-peak hours. But that's pretty generous; most power companies don't even like 1 : 1.

    If you put enough PV on your home, you can eliminate your electric bill. At which point, many utilities argue, the costs of maintaining the grid (that's rolled into your electric bill, but not as a separate line item) are covered by the less-wealthy. The poor are subsidizing the grid for the wealthy, they argue. And they argue, further, that they should be able to charge people who are using Net Metering even if they ARE producing as much power as they're consuming.

    Where I live, I pay a monthly connection charge ( < $20 / month) + $0.085 / kWh. In short, my electrical co-op breaks these out as separate line items on the bill. Even if I put in enough PV to go Net Zero, so long as I'm connected to the grid, I'm at least paying the monthly connection charge. The Arizona utility wanted a connection charge / kWh installed PV, to the point that the homeowners who installed the PV ended up paying the same, without or without the PV. In short, they wanted to eliminate any incentive to add PV and connect to the grid. They did get approval for a connection charge / kWh installed, but it was a fraction of what they wanted.

    In Hawaii, where power is routinely $0.39 / kWh (it's made, largely, from imported petroleum), solar PV and Net Metering are so widespread that entire neighborhoods are producing excess power during the height of the day. It's to the point where HECO gets to veto whether or not you can add PV to your home; you have to get permits from them and they're getting harder to acquire. Because the transformers which convert distributed power (typically lower frequency and higher voltage) to the household power (60 Hz / 240 VAC split-phase) are made to work efficiently, one-way. Going the other way, they are considerably less efficient. If you are a net producer and your neighbor is a larger, net consumer, you're supplying your neighbor and the local transformer simply converts less power going into that neighborhood. When the entire neighborhood is a net producer, the transformer has a problem. So they limit how much power can be produced in each neighborhood.

    I used to think this was all about the power/utility companies trying to defend their bottom line. That's still part of it, but I've come to realize there are technical reasons, too. Installing efficient, bi-directional transformers would require:
    1. installing a second, bi-directional transformer
    2. taking down the power to an entire neighborhood while they switch over
    3. decommissioning and moving the old transformer

    at considerable expense. And that latter part, well, you KNOW they're not going to let their executives and/or shareholders eat that cost. And many utilities are regulated, such that they have to get approvals for rate increases. Which aren't easy to get. So there's technical reasons AND financial reasons for the utilities to grip.

    Put a battery pack on your home, like one of these. Get an inverter which feeds excess to the battery and NEVER exports to the grid. The power company loses their only technical reason to gripe, because you are no longer doing Net Metering. At that point, it's all about the Benjamins.

    Indeed, if you get to the point where your home is truly Net Zero, long-term, you can go completely off-grid. At which point they no longer have a say in the matter.

  • Batteries (Score:5, Interesting)

    by ledow ( 319597 ) on Friday May 01, 2015 @09:30AM (#49592651) Homepage

    It's about GBP30-40 for a 100Ah 12V car lead-acid battery on a random site. These are mass-produced, cheap and easily available. Granted that they are heavy and large, but... scaling up... that's 1.2KWh alone. We'd only need ten car batteries to match it. That's GBP300-400.

    Why, then does it cost the equivalent of nearly $3,500 (GBP2200) for the same here?

    Sure, we allow leeway for different voltages (necessary for high-current loads, etc.), different technologies, deep-cycle, etc. but... that's a five-to-seven-fold increase over what we're using now for quite basic solar, wind, etc. power storage and can be obtained from any garage. And 10 car batteries aren't prohibitively large, expensive, difficult to handle, etc.

    With 10 year warranty and 2KW peaks? That's way within range of such a pack. Hell, stick a decent split charger / inverter on the end, one designed for home use, and it still comes nowhere near the price of this home battery.

    Is my maths wrong? Have I missed something? Quite what are we trying to sell here apart from an overpriced battery and some electronics on either end of it?

    • Re:Batteries (Score:5, Informative)

      by robosmurf ( 33876 ) on Friday May 01, 2015 @09:41AM (#49592739)

      Lead-acid batteries typically last well under a thousand cycles, and also deteriorate if you deep cycle them. Thus you'd probably need to replace a car battery solution every couple of years.

      This isn't all that much better though. I don't think they have released the actual specs, but these batteries are likely to have a cycle life of around 3000 (which is consistent with the 10 year guarantee as they are unlikely to have a full cycle every day). This is much better than lead-acid, but as you say they are also much more expensive.

  • by Karmashock ( 2415832 ) on Friday May 01, 2015 @10:03AM (#49592957)

    I just did a price check and a 10kwh rolls royce deep cycle system with 4 of those batteries is about 1500 USD. Tesla wants 3000 to 3500. At that price, I could buy 20kwh to 30kwh in conventional lead acid batteries.

    The primary advantage of the Lithium batteries is that they're light. But in a static location what is the point of them? Who cares how much the batteries weigh if they never get moved? They sit in a utility closet somewhere in your house and that's it. I'm really confused as to why anyone would pay DOUBLE for Teslas batteries?

    Am I missing something? Why would I pay TWICE as much per kilowatt hour?

    What is more, deep cycle lead acid batteries can be reconditioned giving them a second life. I don't think you can do that with lithium batteries.

    Help me understand. This makes no sense to me.

    Here is a link to what I'm looking at as competition: []

    How are the tesla batteries better than that for this application?

    • by Anonymous Coward on Friday May 01, 2015 @10:35AM (#49593243)

      The Tesla system consist of:
          - 10kWh batteries
          - 3kW? battery charger
          - 2kW-3kW ac inverter
          - grid disconnect (for backup mode)
          - 3000? deep cycles
          - 10 year warranty

      and you compare it with:
          - 10 kWh batteries
          - 500 deep cycles
          - 3 year warranty

      and wonder why your system is cheaper? Really??

    • Lead acid batteries can't deep cycle.

      You operate them in a 30% - 90% range. If the charge drops below 20% - 25% you can throw them away.

  • by future assassin ( 639396 ) on Friday May 01, 2015 @10:12AM (#49593037) Homepage

    to power 2 600W HID lights bulbs to grow weed off the grid. The battery would pay for itself in one crop of 8-10 weeks.

  • by Cajun Hell ( 725246 ) on Friday May 01, 2015 @10:28AM (#49593199) Homepage Journal

    store up to 10 kWh of power.

    ..who doesn't even know the difference between power and energy. And you want to sell me batteries? Don't go bragging about how ignorant and incompetent you are, or at least don't let potential customers hear it.

  • by sribe ( 304414 ) on Friday May 01, 2015 @10:54AM (#49593405)

    On the prior article before the announcement, I posted about the economics not being that compelling, using my own actual numbers for consumption and peak vs off-peak pricing. I also noted that in some states, CA in particular, when peak pricing is ~60% higher than where I live, that it could start to be somewhat attractive.

    That was all based on the pre-announcement rumored price of $13,000 for 10KWh. At $3,500 for 10KWh, I'd be looking at a 4-year payback, or, in other words, about a 25%/year ROI. To be clear, that's without solar PV panels to generate electricity, that's strictly charging the battery during off-peak hours and then running the house on it during peak hours. (Quick calculation based on battery price alone; total installed system more likely to see 15%-20% ROI, but still, not bad.)

    I had wondered what Musk was up to and if the rumors were correct. Because you can already buy a 10KWh nickel-iron battery system for $13,000, so it did raise the question of what was the point? Well, now we know the point--1/4 the cost of existing competitive systems.

    One big question not answered by the linked article, is what technology is used and what's the depth of discharge without damaging the battery. With nickel-iron, you can discharge most of the charge safely. With lead-acid technologies, you can't go below about 70% without shortening the lifespan. So 10KWh can actually mean anything between 3KWh and 8KWh of usable power--a huge range. (Hey, maybe Tesla's going to be consumer-friendly here--maybe 10KWh means 10KWh of usable power... As this kind of thing becomes more common in the home, it would make sense to rate battery systems that way, to make direct comparisons easier...)

  • by davidwr ( 791652 ) on Friday May 01, 2015 @11:46AM (#49593901) Homepage Journal

    If I'm a "wind/solar" or other non-24x7-generating company and I know what fraction of my customers have a several-hour-backup power supply, I can offer them lower rates in exchange for "turning them off" or even "buying electricity back from their batteries" in times of peak demand. This will let me offer services to more customers than I normally could handle.

"If you lived today as if it were your last, you'd buy up a box of rockets and fire them all off, wouldn't you?" -- Garrison Keillor