Tesla Sends Out Invites For “The Missing Piece” April 30 Event


On April 30, Tesla Motors will make what’s believed to be a home energy and utility-scale battery storage announcement.

That announcement, called “The Missing Piece” by Tesla, will take place at the Tesla Design Center in Hawthorne, California at 8pm Pacific Time.

With the electric car from Tesla and solar from SolarCity, the missing piece is energy storage.

Tesla Home Battery

Tesla Home Battery

Tesla sent out last-minute invites (emails sent yesterday) for the event to current Model S/Roadster owners. The event is now booked to capacity.

We’ll cover the announcement as it occurs on Thursday night.

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49 Comments on "Tesla Sends Out Invites For “The Missing Piece” April 30 Event"

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In English units, 31.5″ H x 13.8″ W x 10.2″ D

Weight = 176lbs

Obviously not English but Imperial system

“I’ve always found it amusing that the 3 countries that officially cling to Imperial units are Liberia, Myanmar, and the United States. Quite a motley crew! ”

Canada Australia even UK use metric system , mostly.

Just saying.

“In English” is an expression to explain something in terms that someone would understand.

someone’s got some ‘splainin’ to do.

Got it.

Sorry, I misunderstood.

However, “In English, that is … ” would’ve been an indication to your interpretation, but the writer didn’t say that but rather “In English units”, as if the imperial system should be prefered in English – that triggered my (hasty?) reaction.

All the best

I’ll just say “in inches” next time 🙂

Or join the 6.7 Billion people on Earth that use Metric 😉

I actually use both, but my visualization of size/distance/weight is still best in inches/miles/lbs. Product of where I was born/raised.


Actually USA does use the metric system. And the English units system. We half-converted to metric 40 years ago, then (for reasons unknown) the conversion stopped. Since then, we have used both in a random fashion. It sucks.

“Would you like a one-liter Coke or a 32 oz drink?”

At the rate our government-schools are failing the USA, our conversion to metric will probably never be complete. On the bright site, although our government-educated kids are stupid, at least they have good government cell-phones to coordinate looting campaigns:


@Open-Mind. Even more confusing is “Be sure to pick up a gallon of milk and a 2 liter of Coke.”

Don’t worry all of you non-metric-guys: your strange oz/inch/lb/wtf-system is a good way to prevent industry espionage. Obfuscation is sometimes better than encryption 😉

…and it keeps us metric-people from suffering brain-detoriation induced by the lack of practice in calculating back and forth from wtf to metric 😉

and btw: we got quite used to use non-metric measures for screen-sizes or tubes and fittings, so we are also kinda hybrid-minded.

Pretty heavy to mount on a wall without a pad to the floor/ground. Only one stud can be hit with 16″oc construction unless there are flange mounts. Probably needs to be strapped (like a water heater) in earthquake areas.

WATCHING/ “”A conservative estimate is that we have an amount of electricity unused at night that’s equal to the output of 65 to 70 nuclear power plants between 6 p.m. and 6 a.m.,” Senator Lamar Alexander (R-Tenn) stated before the Senate Energy and National Resources Committee. “I suspect that’s probably our greatest unused resource in the United States. If we were to use that to plug in cars and trucks at night, we could electrify 43 percent of our cars and trucks without building one new power plant.”” Ed. Now if only there was only some way to store this massive, daily, off-peak, wasted, Over Generation of electricity, for base load peak energy demand… Link Goes To Torque News And Full Report on US Senator Lamar Alexander (R-Tenn)Statement Entered Into Congressional Record, 05.19.2011- http://www.torquenews.com/397/senator-alexander-unused-electricity-our-greatest-national-resource #GigaLithium ———]= PROOF OF CONCEPT? / “Our Storage Product will be available again in late Summer 2015. We’ve filled all of the spots in our Battery Storage pilot program and we won’t be adding any more sales for the time being. So far through the program, we’ve installed 300 systems, and plan to finish out 130 more in early 2015. We’ve been getting great feedback from… Read more »

99% of countries in the world use the metric system, the USA Government wanted to change but found that their citizens were not educated enough to cope with the change. Now would be their chance to catch up to the rest of the world.

$/KWh predictions anyone (including all components)? I say $325.

From what I read somewhere it will be $1,500 down and then $15 a month for 10 years. Until now it sounds reasonable, but guess what, after those 10 years, battery goes back to Tesla. I don’t know if I like that. Hopefully that 10kwh pack will also be for sale for a reasonable price…

If you’re concerned at all about battery degradation, a ten year lease for cheap sounds pretty good. You get the benefits for ten years, and then the diminished battery is Tesla’s problem and you’re free to look at systems that are more advanced by ten years.

IMO Battery degradation is not as big a deal in household energy storage solutions than it is in e-mobility solutions. I would also prefer a non-leasing solution. (In fact I already have one based on “degraded” conventional 12V lead-acid – cheap as hell, combined with solar panel and led, It’s fun and it’s cheap!)

But why are they sending invites to Model S/Roadster owners? Why Tesla and not SolarCity?

There has to be some sort of EV tie-in here. We’ll find out soon enough I suppose!

The thing supports multiple communication standards to talk to a wide variety of Chargers / Inverters…

I’ve always wondered about two things:

1) Could owners of a home battery like this use it to DC charge their Tesla cars? Like a short burst home supercharger that gives them a few KWh in just a couple minutes.

2) Same thing as #1 but offer it for other Tesla owners to use too. Sort of like Plugshare but for Tesla DC charging. If you’re running low on charge you could pull into a fellow Tesla owners driveway and grab a few KWhs in just a couple minutes.

Number 1 is a real possibility. There was someone in TMC considering installing a CHAdeMO charger at home (they actually got 480V 3 phase service) so they can do a quick charging daily.

If Tesla combines a home battery with a home supercharger, they can potentially provide something similar except without the requirement of needing expensive commercial power service at home.

However, even without quick charging capabilities, I can see a home battery working to allow owners to take advantage of offpeak rates.

If you need fast charging, then your battery must be low, so you would need eight of these units to get you where you need to be.

Probably not, at that low voltage.

120A at 48V gives you roughly 5.7 kW

Not sure if that is already called super-charging, but at least it is something (and IMO more than 32 A at 120 AC)

… but maybe combining that lousy 3.8 kW from 120 AC outlet with the 5.7 kW from home storage would be a solution to at least semi-quick-charge 😉

I hope it communicates with yout Tesla car and can use it’s battery as extension when parked at home and plugged in. Power flows both ways.

Great benefit: infuse free SC-power from your Tesla into your home storage :O

Keep in mind there is a limit to how fast battery packs can be safely charged. Too fast, and they overheat and possibly burst into flames.

As I recall, the rule of thumb for Tesla Supercharging is a 60% charge in 30 minutes (minimum), so that’s 1.7 kWh of charge added per minute. To transfer 80% of the power in this 10 kWh storage unit (or 8 kWh) at the same rate would take 4.7 minutes. (Note the transfer involves some loss; rule of thumb seems to be about 15% inefficiency, but perhaps someone else can provide a more precise figure based on experience.)

I don’t know if that’s the fastest safe charging speed, but my guess is you shouldn’t do it much faster.

Now, the question I want answered: Just what equipment would you need to safely handle such rapid charging? Do they make EVSEs that can handle that level of power, and if so what are the prices?

is it confirmed 10kWh? IF so 2 Model S battery “strings”…

agreed, are these the final specs?

Or are these the specs for the pilot project work done previously?

IMO, a pack that small doesn’t make any sense. It needs to be much bigger, at least as an option. Big enough to fast-charge an EV, and serve as a couple-day hole-house UPS, as well as balance an array of solar panels.

There seem to be a missing zero. 100 KWh instead of 10 KWh. 10 KWh gives you a protection for a small power outage. 100 KWh give you possibility for fast charging your ev, for storing a whole day of PV production, for going through at least 3 days of power outage even more if PV production is balance your use. 100 KWh packages are also more in line with a model S battery pack size which is handing for similarity in control electronics component size and type.

I like that these are so small, and that they can be strung together. Three of these together, charged by solar while I’m at work, would give me enough power to run my whole house and completely recharge my Volt every night. As a kicker, it would take up a barely noticeable amount of room on my basement wall next to the breaker box.

You would pay that much for 3 sets of the system?

I thought 10 kWhr was too small a capacity, considering my pretty efficeint house uses ~ 450 kWh / monthly in the milder seasons. If I was to have an EV that needed charging for my 20 mile commute, I’d need another ~ 10 kWhr for that.

I hadn’t considered daisy chaining them together for extra capacity, but if possible, it would allow you to buy in a little at a time.

If using with a grid tied solar system, it would still need something like SMA’s Sunny Island to power the house. Good thing you can team 2 Sunny Islands to get more power and have 240v capacity.

should’ve said 20 miles each way commute

only the off peak makes a good point.

The UPS aspect also appeals. Sure, you wouldn’t use it for that purpose 99 percent of the time, but we’ve all had power outages and they’re annoying, so it would be a godsend when that one percent hits. It would just be a nice additional benefit besides the peak load shaving.

For potentially $1K and additionally monthly fee?

I am NOT sure that is a good deal.

Then again, Tesla owners don’t always care about having “good deals”. They can afford to try…

Peak load shaving can be a great deal. Electricity during peak hours can be significantly more expensive, depending on your rate plan and your area. For example, I pay 9-11 cents per kwh during super off peak hours and 27-39 cents during on peak hours, depending on the season. Transferring all my peak energy use to super off peak by virtue of charging the battery at night and using it during the day would be a very good savings, and the UPS feature would just be a bonus.

Did anyone notice that it is a 48V system?

It will require another inverter to make it work with your home.

That will cost addtionally up to $1500.

Not to mention that 120A DC with 48V system is only 5.7kW. That is only 24A at 240V. Barely can keep your A/C running. Certainly aren’t enough to keep your appliance running with A/C on…

But if the system cost less than $800, then I might think about it.

Another thing I wonder is that how does the system maintain the charges…

Li-ion battery life is signficantly shortened if you kept it at a high level of charges. But that is exactly what a battery backup system needs. So, unless only 60-80% of the full capacity is used, then the battery will degrade even if it is NOT used by simply parked at a high level of charge…

If it is only charged to 60-80%, then there are a bit of kWh capacity “wasted”…

But it’s perfectly normal for a certain portion of a li-ion battery pack to be reserved, or “wasted” as you call it. You don’t want to charge a li=ion pack to 100%, and you don’t want to drain it to 0%.

Whether or not that is actually “wasting” capacity is merely how you choose to view it. A reasonable view would be that it’s not “wasting” anything if it preserves long-term battery life.

For example, a Tesla car reserves 5% capacity at the top. You can only charge the battery pack to 95%, even at max range setting. I’m sure there’s a reserve at the bottom too, but I’ve never been able to find the an authoritative figure for that.

You can be sure the Tesla home storage unit will also have a built-in limit to charging and discharging, also less than 100% and greater than 0%.

I was watching a video of one of the recent (within pas 12mo) videos of a presentation by JB Straubel. In it he mentioned that they were doing their own utility inverters because they already have all the necessary experience with motor inverters. The unit and specs shown in this story clearly show that it is just a battery and depends on “industry standard” 48VDC nominal ON/OFF-Grid inverters. I was hoping for a complete system from Tesla.

My grid-tied inverters will only output power when the grid is stable and reliably providing 60Hz AC. I wonder, will this system be stable enough to keep my existing solar panels producing even when the grid is down? Or will they have to play games with Solar City to design a holistic system that does so?

In other words, is this plug-and-play with existing installations, or does it require a whole new system? A question which may or may not get answered tomorrow.

This system is less about EV and more about managing grid demand. As the peak demand for electricity grows utilities create rate structures that charge the customer based on WHEN they consume electricity. This is done with a “demand” charge or “time of use” pricing. (A kWh during the yearly demand peak costs the utility hundreds of dollars yet the cost of a kWH that same night costs a nickel)

This home battery will simply allow you to get on a time of use rate (TOU) and reduce your bill and grid stress. This reduces the need for new generation and adds value to existing generation. A utility might create an incentive for these system to be installed as they can save them up to a thousand dollars a year.

My local utility offers a TOU of $0.29 to $0.36 tried on-peak and $0.06 off-peak. So if I charge my EV and house at night and 66% off standard service. (yes, I know the purchase of the system will out way the savings but it also doubles as a backup to the grid going down and those system are not cheap)

Typo “So if I charge my EV and house at night I’ll save 66% off standard service.