Published on February 21st, 2015 | by Zachary Shahan


Tesla Home Battery On The Way

February 21st, 2015 by  

One of the biggest statements on Tesla’s last quarterly conference call was that it would be unveiling a battery storage system for home use within 1–2 months. I know that several competing energy storage companies are watching closely to see what the details (especially price) end up being… while surely also being a bit envious at how easily Tesla gets press and big stories in the biggest media outlets. But, with presumably the lowest-cost lithium-ion batteries on the EV market and a track record of wonderful products and business practices, no one can say that’s not at least a bit warranted. Still, I’m super eager to find out how Tesla’s upcoming battery competes. We shared the Solar Love story below in a couple of roundup posts this week, but I know many of you didn’t see that. (Meticulously scan those roundup posts! We’re cutting our reposting of content a great deal these days.) To make more of you aware of this big story, here’s what I wrote last week:

We’re gonna unveil the Tesla home battery, or consumer battery, that will be for use in people’s houses or businesses, fairly soon. We have the design done, and it should start going into production probably in about six months or so.

We’re trying to figure out a date to have the product unveiling — it’s probably in the next month or two. It’s really great. I’m really excited about it.

tesla-storage-unitThat was Elon’s statement regarding the next step of electricity storage for Tesla Motors. Of course, this product is sure to be available with SolarCity solar panels, as well as separately.

So, without more details until the unveiling, we can’t provide much more info. However, a bit of context could be helpful.

Within the electric vehicle market, Tesla is expected to be using the lowest-cost batteries. The battery cells come from Panasonic, while Tesla turns them into battery packs. There’s a lot of competition in the electricity storage market, but there’s a good possibility that Tesla could offer some of the most competitive consumer batteries on the market.

As of right now, it makes little financial sense for the large majority of people who go solar to also get a battery storage system and go off the grid. However, it is widely expected that, with solar panel costs continuously coming down and battery costs doing the same, that day could come about for millions, tens of millions, or hundreds of millions of people before too long.

For now, it would be assumed that these Tesla batteries would be targeted at homeowners interested in backup storage in the case of an electricity outage, or for people who are way off the grid and would have to pay hundreds of thousands of dollars to have the grid extended to them. But, who knows, perhaps the cost of Tesla’s batteries is even better than most of us think….

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About the Author

is tryin' to help society help itself (and other species) with the power of the typed word. He spends most of his time here on CleanTechnica as its director and chief editor, but he's also the president of Important Media and the director/founder of EV Obsession, Solar Love, and Bikocity. Zach is recognized globally as a solar energy, electric car, and energy storage expert. Zach has long-term investments in TSLA, FSLR, SPWR, SEDG, & ABB — after years of covering solar and EVs, he simply has a lot of faith in these particular companies and feels like they are good cleantech companies to invest in.

  • ken29

    I understand the interest in Lithium batteries in cars (I use them in model airplanes) where weight and volume are critical (in varying importance), but there is no reason to spend the extra money for a battery that is going to set on a solid land-based floor. A modern gel-cell is a lot cheaper, has roughly equivalent shelf-life and cycle-life, and is nowhere near as temperamental while charging (or discharging), especially when a circuit fault (aka short) occurs. Lithium makes a very, very hot fire that can’t be extinguished with any normal fire extinguishing tools. After a load of Lithium batteries brought down a 747, a fire protection consultant said: “They explode,” Back said. “They shoot fireballs. They emit smoke. Sometimes they spray flaming liquid.” At least if they are in your car, presumably, you can stop it, jump out, and run.

    • Bob_Wallace

      There are a few hundred thousand EVs on the road these days. Here about any shooting fireballs?

  • Alan

    If everyone goes off grid you will be charged for the electricity supply for street lighting traffic lights etc etc etc. Will be just another tax probably on your rates. There go the savings

  • Nathen

    I have to wonder if this new home electrical storage system is related to a system that was presented a while ago from a fellow talking on stage in front of an audience how a group of scientists he represented had developed a unit to store electrical energy without batteries, along with a nano carbon fibre to transmit the electrical power. Hmm, I will have to see if that video is still viewable on YouTube.

  • Marcus crouch

    I have the perfect tree house concept you could use to realy unveil a green style life. This battery powering my tree home would be a green dream come true !!!

  • Kakarot

    This battery is going to be rad. I would like to see an entire society functioning off self-sustaining energy, everybody off the grid. Then maybe money won’t control everyone’s lives and we can flourish. It’s inventions like these that terrify our governments and threaten their reliance on monetary gains. Stick it to the man!

    • Bob_Wallace

      Going off the grid doesn’t make sense in most cases.

      Going off the grid means that one loses access to wind, hydro, and geothermal inputs. If you’re thinking about going off the grid with solar then you’re going to have to find some sort of backup generation and that basically means running a FF generator.

  • Alibaba Neue-Welt

    It is possible to get data sheet from the new Tesla home storage system ?
    Price per kw/h ?

    • vensonata

      Deep silence…nobody knows. That’s the fun part. You get to guess, spread rumours, argue. Its good for business apparently.

  • Larry


  • Can we talk about ultra or supercapacitors, because they will help by about 10% in fuel consumption? How much longer will the battery last with them?

    • vensonata

      Peter, I was about to dismiss the ultracapacitor idea with “way too expensive etc. etc.” But wait a minute. I did research the whole notion a while back…but here is the thing. Ultracapacitors have at least 500,000cycle life, and don’t seem to have a calendar life. They do bleed energy if not used for even a day, but with cycling daily that shouldn’t be a problem. They are, when last I did the arcane math comparing to kwh about $1000 kwh. But that is what the Euopean cost for lithium packs is. So yes it actually might be that ultracapacitors are ready for household storage. Their price and widespread use wil make us rethink the whole issue. Thanks for the thought.

      • Joe Viocoe

        What about the energy density?
        Where can you buy capacitors at $1000 /kwh ?? ( I don’t think Europe is paying that much for Li-Ion at the cell level).

        • vensonata

          Joe, Ya, Europe is paying that much, price the Bosch home storage unit or the Sony unit. The Germans have arrived in the U.S. with their beautifully engineered pack, which includes an inverter and it is just silly in price! Something like 4.5 kwh for $12000!!! Insane, right? Ultracapacitors are all rated in Farads (how bloody convenient, thank you nerds!) I in my totally inept way attempted to translate into kwh. I got about $1000 per kwh. Do not trust me! But please, if anyone out there is a real engineer I’d love to hear the math/economics done properly. Report back ASAP.

      • eveee

        They need electronics specific to caps, an extra cost. The voltage is discharged. To get a constant voltage output, you need a converter.

  • Ticobird

    It will be a real hit if they price this product correctly.

    • The key tidbit I’m eagerly waiting to see…

    • Rhonie Briley

      No matter what the initial price will be, I am sure once Tesla gets their battery plant up and running the cost should drop dramatically. Really the only reason I have not switched to solar for most uses is because the cost, handling, and the reliability of storage. I am sure many people will convert to solar if the price was low enough. The advantages, using an electric car, and powering their own residence would definitely reduce everyone’s cost of energy. Just providing low energy cost will definitely kick the economy in the butt. For myself, I would rather put in a swimming pool than paying a high power bill.
      I am looking for a decent newsgroup that discusses all kinds of alternative power sources. So if you or anyone else knows of one, please reply to this post.

      • Offgridman

        Vensonata mentioned one just a couple of comments above or below yours (depending on how your browser displays)
        Green Building Advisor has many threads that can be referenced, or you can submit individual questions for your particular situation that people will be happy to advise you on.
        A little searching can find you several sites that advise on all aspects of green building technology at various levels in of technical expertise. Everything from specific cost and energy use analysis from University studies to basic techniques for the non engineering home owner.

        • Rhonie Briley

          Thank you, I will take a trip over to “Green Building Advisor” now. I have done a lot of searching for Alternative energy sources, however, too many to mention are outdated. Many of these sites are far behind today’s technology. For this is the reason I am looking for forums that people provide input on a regular basis.

      • firedrake911

        Concur. Of course the next challenge is to get your state to allow you to go off grid… If you want to go completely off, no problem, but California and their utilities work under the premise that having systems that can go off-grid hooked up to the grid is evil.

        And don’t forget. We’re the bad guys.

        If we put solar on our roof, then we’re ripping off the poor folk who can’t afford solar, and therefore use more utility based electric. And that means we’re not paying our fair share of the infrastructure.
        Shame on us. Of course utilities paying retail for the excess electric from people’s solar, is silly to begin with. When that goes away, that will affect the value proposition of on-grid systems.

        Is it true that most energy rebates by US gov, and states is only for on-grid systems?

        • Rhonie Briley

          Can you say a “poor tax”? I am sure they will come up with some kind of tax, that will be just is high is an electric bill. Think about this – Maryland taxes you on the rain.

  • Bryan

    On the way but at what cost? L-ion will never pencil out without a massive financial incentive from the utility or state at today’s prices. That’s a fact.

    • vensonata

      Ah Bryan, the economics of battery life. Welcome to the fun house! Here is my school boy math. Lifepo4 from Balqon complete pack with battery management (but not inverter) $350 kwh. 3000 cycles to 80% with little degradation. Another 2000 cycles available with perhaps 60% capacity. So 3000×80%= 2400 and 2000x 60%= 1200. Total 3600 kwh for $350. That is a little less than 10cents kwh. Not bad, quite competive with grid at say 18cents. Combine solar Pv at 10cents and battery at 10cents and you are producing your own solar garden for 20cents kwh. That makes the utilities start to sweat!

      • Scott Hays

        That’s one of the things that has made it difficult to switch to solar while on grid in my part of Colorado. You can be on grid for .14 or less per kwh, which makes it really hard to switch. However, for the business we are getting ready to set up, we plan on going ahead and building solar and other passive methods from the get go. Might as well do it right from the bottom up.

        • Vensonata

          Yes Scott, I have been off grid for 15 years running a large meditation community. We run on 11.4 kw PV and a 40kwh AGM battery bank. A diesel generator for back up runs about 35 hours per year. $100 worth of diesel per year. We live elegantly with all the modern conveniences, no problem. Heat is wood. So with a few considerations it is neither expensive nor difficult to live off grid. However you do have to be conscious and sensible about electrical use. you can easily use 50-75% less than the ordinary house without noticing any loss of comfort.

      • My 2 Cents

        I don’t think it is as simple as 2+2=4 I don’t think you can just add the two 10 cent costs as one. One is used during the day and the other is used at night. There might be carry over though. My problem with batteries is can I cover all of my wants and needs such as central air heat electric oven. you see I don’t want to use less energy I want to be able to use as much as I want. Can batteries handle the startup cycle of these items and the carry on wattage to keep them going as needed. Cost be damned I realize I can’t do it through SCE at what they charge. 1 month I recall we (2 people) had a 1400 Kwh Month I believe over $500.00 bill. We were only comfortable about 20% of the time. The house is only 11 years old we use fluorescent in everything except one bedroom fan that only see’s 8 days a year use. I know LED’S would be better.
        Anyone offgrid with more than a cabin say 2200 sq.ft. and if so what did it take. I don’t want to burn wood and if possible no natural gas or propane.

        • rtfazeberdee

          You’ll need to install proper insulation and triple glazing. Here in the UK, we are just catching up with the Scandinavians on this score. There are new houses here insulated to these levels that are not using heating/cooling at all and the house remains about 18C, they tend to have a log burner just in case as it looks good. That will take the strain off any power system. The tend to have heat recovery ventilation systems as the air needs to kept fresh as the house will very few leaks.

        • Ticobird

          WOW! That is a high price for electricity. Do you live in the US? Your cost works out to $.357/kWh which is a little more than four times what I pay for electricity where I live – North Alabama.

          • My 2 Cents

            S.C.E. Hemet SoCal. Summer is about .33 during the day. When we use the most air.

          • My 2 Cents

            Sorry it is not quite .33 they are getting 12.4% more over 3 years. .93 cents a day besides I read.

            Tier 1. .15 to 386 KWH

            Tier 2. .19 to 501

            Tier 3. .26 to 771

            Tier 4. .31 772 above

            2015: $206 million (or 3.3%) increase over 2014 authorized rates

            2016: $318 million (4.9%)

            2017: $317 million (4.7%) increase

            Total: Cumulative $ 841 million (or 12.4%) increase over 3 years

        • vensonata

          Oh man, this is fun. This conversation on what is possible with off grid pv is central on some very good websites. Try “Green Building Advisor”. You can submit any questions you like for free and 5 or 6 people with long experience will answer quite extensively. I might even show up!
          In brief, because your electricity rate is so high you have a perfect opportunity for off grid. Heating is the most difficult problem for Pv because in winter when you need it most is the least sun. But don’t give up….times have changed and her is the remote leading edge solution. 1) a 10 kw Pv array optimized for winter angle 2) an air source cold climate heat pump 3) 2000 gallons of hot water storage. Between the three, if, and only if you have a super insulated house you might make it. But if you need back up propane it is trivially cheap to give you at least mental comfort.

          By the way, our house is over 10,000 sq ft and we run it with comfort and ease.

  • vensonata

    Most off grid people are salivating at the thought of lithium batteries, (these are lithium iron phosphate 4, I believe). The reason, oh griddies, is that lead acid doesn’t like to “hover” at less than full recharge. But full recharge on a cloudy, winter day won’t come from your PV panels. It comes from a gas, diesel, or propane generator. And it is expensive and wasteful since lead acid refuses to eat what it is offered in the upper 15% of its charge cycle. The generator runs for hours, the battery coyly sips the lobster dinner you are feeding her and you end up with the bill. But Lithium, ah lithium, there is a different story. Lithium loves snacking and never being full. It is a good eater and cleans up its plate with gusto…accepting a full charge up to the last 5% and not being sullen if you don’t finish the charge.
    But, my fellow off-gridders, don’t get out the banjos and fiddles yet! There is a fly in the lithium ointment. The fly is called “calendar life”. These lifepo4 batteries will last for 7-15 years, (but nobody really knows!!!) If you have two days worth of storage, for cloudy times, that will be 25-30 years. But read the “best before date” on the side of that giant bottle of vitamins you got on sale. Alas, it expires while still 3/4 full of pills! Damn! There goes the savings.

    Do not despair. You can hybrid your jewel of a lithium pack with your grumpy, short cycle but long calendar life lead acid bank for the back up 2 or 3 day storage in winter. Your lithium performs the daily storage nicely, but needs to be used up by frequent daily cycles to make sense. Enough.

    • Neptune

      What happens at the end of calendar life?

      • Bob_Wallace

        What is calendar life? How do we know that it is real?

        Why does it happen, if it does?

        Is there any chance calendar life is a myth?

        Might it be like “solar panels have to be replaced after 20 years” which is obviously untrue and seems to have come from warranty lengths?

        • Neptune

          Well, I don’t know, that why I’m asking. 🙂

          I know what happens to lead acid – they gradually degrade until someday they just stop working. I don’t know about lithium.

          • Bob_Wallace

            Lead acid batteries degrade with cycling. As do lithium-ion.

            Do lead acid batteries simply die because they are old?

            I’ve been looking for something on calendar life and so far I haven’t found anything convincing. Most of the stuff basically says there’s calendar death but go no further.

          • vensonata

            See, its important information and nobody seems to know much about it. Its obviously a factor in food and medicine. And its good to know that your dog will probably not make it to twenty so don’t build him a dog house that lasts for 100 years.
            Saft batteries (French, but used in German home storage) says lithium battery calendar life is 5-15 years. That’s rather vague, isn’t it? But if true, rather important. We know that the Ambri liquid battery has calendar life beyond 30 years…that’s important info for any investor to know.

            I invite the bright readers of Clean Technica to find out more…because I don’t have time to be a battery detective.

          • Neptune

            According to Wikipedia Nickel-Iron batteries last for 30-50 years. This is quite impressive.

            I can’t find anything useful about Li Ion.

          • eveee

            Li ion has cycle life. Capacity degrades with cycles. Look up Winston batteries, they give curves for it.

          • vensonata

            Bob, I am now more informed after reading (can you believe it!) a German Masters thesis on Lithium calendar life. Its worse than I thought, man. They seem to conclude, though I find it unbelievable, that the calendar life is 6 years!!!. Saft Battery manual say “battery calendar life degrades 5% first year, 3% each year after. At 6 years 80% has been reached and is now not suitable for continued EV use.
            Well, what can I say, it sounds impossible, and I don’t like the news, and aren’t there 6 year old roadsters running around? But whatever…it is important to understand something like this before you drop a wad of cash on an EV.

          • Bobby

            so lease the car for less than 6 years…

          • i think it’s important here to note that there are huge variations amongst the many lithium-ion batteries on the market. i imagine that extends to calendar life as well. when i visited the Younicos facility, i was shown test results for a number of different lithium-ion batteries. we weren’t allowed to take pictures, iirc, but there were HUGE differences.

            edit: btw, Younicos ended up choosing Samsung’s lithium-ion batteries for its facilities.

          • Bob_Wallace

            How about contacting them and ask how they test for calendar life? Do lithium batteries die of old age or are they worked to death?

          • vensonata

            Zach says “we weren’t allowed to take pictures” Hmmm? Battery markets could be a delicate matter, big money at stake, rumors of flaws could damage business etc.

          • Bob_Wallace

            Protecting manufacturing processes is common. Best to not release photos of your line and tip off the competition.

          • Bob_Wallace

            I’m not buying 6 years. The Roadster started selling in 2008.

            I’d suggest you read carefully. Look for calendar life in which the batteries are held at a, say, 80% charge, not cycled, and not cooked. Everything I’ve found is confounding battery age and cycling.

          • vensonata

            I read carefully, mostly because I don’t believe it myself. The conclusion is from the manufacturer themselves…Saft battery. The thesis just quotes the information from Saft. This is all news to me since I am a big fan of Lifepo4 as you know. But note that I haven’t actually bought any yet!
            I think I still might buy a small bank of lifepo4 from Balqon but it would be just enough to scrape through a winters night…maybe 7kwh. Strangely, lead acid seems to be better for back up occasional 2 or 3 days cycle. I have that already, thus a hybrid Lifepo4/ AGM lead acid seems the most sensible at this time.

            Also look at the actual statements by Tesla about the Roadster battery “expect 30% capacity loss over 5 years and 50,000miles” Also they recommend a pre-purchased replacement battery for $12,000. Very few roadsters were sold before 2009 and there were only about 2500 total sold..most between 2010 and 2012. So that’s all I know.

          • jeffhre

            Clearly the the 10 year old Tesla Roadsters are dead 🙂

            Without controlling charge and discharge levels and keeping them in a nice comfortable temperature range, Li Ion batteries never made it past 10 years. Considering most testing was designed to determine when they would expire, and not how to make them last longer, researchers had gotten the results they were looking for.

          • Ken

            Tesla batteries have a sophisticated temperature control system that make them last a very long time.

            There are many Roadsters with over 100,000 miles and plenty of battery range.

            Recent Model S numbers from the Netherlands show that
            after 100,000 miles, the typical Model S is projected to retain about 92 percent of its battery capacity and range.

            The battery should be good for the average driver for about 10 years and the cost of replacing it will be less the the price of fuel and service for a gasoline car anytime after the 8 year warranty ends.

          • Seven of Nine

            You are dreaming. Tesla’s own spec states that they will be under 85% in 6 years. Add the cost of electricity to the battery replacement and you lose money at 10 years.

          • Ken

            You don’t seem very good at basic research or math skills.

            Based on actual data, after 100,000 miles, the typical Model S is projected to retain about 92% of its battery capacity and range with loses then shrinking to only 1% every 30,000 miles after that.

            The average US driver travels about 13,300 miles a year, so the Tesla battery will easily last 8 years and is actually on track to last well over 10 years – exactly as I said.

            Any replacement after even 8 years will still save money in fuel and maintenance costs for a gas car over the same period – exactly as I said.

            It would seem that you are the one dreaming – or lying.

      • Bobby

        recycling if you dont want to keep using 80% capacity batteries

    • Steven F

      There is a veryinteresting presentation about lithium battery life:

      Basically scientist are studying the chemistry and failures of batteries and developing better testing methods. What they are learning is being applied to current production. So that new batteries today are vastly better than batteries made a few years ago.

      • vensonata

        Wow, Steven. What an amazing lecture. Exactly on this topic. I advise any others on this site to watch it. This is the leading edge of Battery research…this prof trained the phd’ who work at Tesla now in their battery dept. My basic info was correct, by the way, cycle life is practically meaningless, the chemical reaction shorten battery life significantly and sometimes suddenly! But don’t listen to me, listen to Dalhousie University Prof Engineering partnered with 3m and others for the leading edge. By the way, there is hope for extraordinarily long lived batteries soon to appear!

      • DM SUH

        Thanks Steven for sharing, this is a must watch video for anyone interested in batteries!

      • Seven of Nine

        The Panasonic single cylinder cell that is used in Tesla (thousands of them) is a 10 year old design. The Giga factory is being built to build those batteries. New tech is decades away.

        • Bob_Wallace

          No, Tesla apparently has a new battery.

          Plus battery chemistry has been changing over the years. Only the packaging has stayed the same.

    • LifeonBatteries

      Finger crossed on all battery life, I’ll stay with lead acid .

    • Seven of Nine

      Tesla does not use LiFe they use LiPo which has higher energy density and lower weight. I’m pretty sure their home battery will use the same tech.

  • Volkmar Kunerth

    Makes only sense since it is the missing link controlling the whole supply chain.From clean energy production to storage and electric mobility.

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