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Elon Musk's 3-Biggest Powerwall Whoppers

05/10/15

  04:49:00 pm, by Jim Jenal - Founder & CEO   , 1451 words  
Categories: All About Solar Power, Solar Economics, Residential Solar, Ranting, Energy Storage

Elon Musk's 3-Biggest Powerwall Whoppers

Elon Musk is a visionary and a showman, but occasionally his enthusiasm for his vision gets way out ahead of reality.  Nowhere was that disconnect more on display than this past week when he made his much talked about announcement of the Tesla Powerwall battery storage system.  While we share the vision for the potential of battery systems (such as the one Enphase Energy is set to release later this year, albeit in a far more understated fashion), when 38,000 people go online to order a product that doesn’t yet exist, it is time to debunk some of the more exorbitant claims made by Musk. 

Here are the three biggest whoppers that Musk made during his Powerwall presentation (video below).

Whopper #3 - Power for an ice storm or other significant grid failure event

Musk touted the “peace of mind” that would come from having the Powerwall, and said, “if there’s a cut in the utilities you’re always gonna have power, particularly if you’re in a place that’s very cold, now you don’t have to worry about being out of power if there’s an ice storm.” (See video at 8:35.)

The Powerwall unit that Musk was talking about that was designed for “daily cycling” was a 7 kWh unit that is priced at $3,000.  The average home in the Run on Sun service area uses 25 kWh/day.  So a single Powerwall unit provides roughly one quarter of the energy demand of an average home.  If your desire for “peace of mind” means running your home for a full day in normal fashion, you will need to purchase 4 Powerwall units (assuming you have the wall space to mount them) and that will cost you $12,000.

Of course, many outages last longer than a day.  The longer you want to stay powered, the more units you will need.

Whopper #2 - Powerwall will work with existing solar systems

Musk insisted that Powerwall has been designed to work with solar systems, “right out of the box."  (See video at 8:25.)

Except… that the Powerwall is designed to fit between existing solar panels and the DC-AC inverter(s) in the system (i.e., on the DC side of the system).  But here’s the thing - the vast majority of inverters are what are known as “grid-tied,” which means if the grid goes down, the inverter shuts off, and stays off until the grid comes back.  If the Powerwall is on the DC side, there is no way for it to “mimic” the grid (which, of course, is on the AC side), and so the inverter will shut off.  While the inverter could certainly be replaced with a hybrid inverter (that can work both independently and tied to the grid) such a replacement is a pricey undertaking and certainly not a plug-and-play installation.

But Musk, like the true showman that he is, saved his biggest Whopper for the end…

Whopper #1 - You can go off grid… for $3,500!

Warming to his subject, Musk really brought down the house with his most outrageous claim of all:

You could actually go, if you want, completely off-grid.  You can take your solar panels, charge the battery packs and that’s all you use.  So it gives you safety, security, and it gives you a complete and affordable solution.  And the cost of this is $3,500."  [Gasps and applause from audience.] (Video at 8:55.)

No.  No you cannot.

Let’s unpack his statement.  There’s two major claims here, neither of which is true.  The first is that you could go completely off-grid, and the second is that it would cost you $3,500.  So let’s start with the easy one to disprove, indeed, we already did above: this won’t cost $3,500.  The Powerwall provides 7 kWh of storage.  The average house uses 25 kWh/day.  If the battery has to run your house for just one day, you would need 4 Powerwall units at a cost of $12,000.  (The 7 kWh unit is the one designed for daily cycling - what you need to go off-grid, and it costs $3,000 - if you could actually purchase one, which you can’t.)

So that’s easy to debunk.  But what about the second, more fundamental question.  Can I use this Powerwall system to go off-grid without changing my middle-class, suburban lifestyle?  For most folks the answer is simply, no.  Here’s why.  When you go off-grid you need to be able to meet all of your energy needs all the time without assistance from your local utility.  To do that, you need a battery system large enough to last you during the longest typical shortfall of available energy (i.e., how many stormy/cloudy days in a row will you see), plus a solar array large enough to charge that battery on sunny days while meeting the household needs.  Turns out, that is quite a lot of both.

Folks who design off-grid systems (very few of which are found in areas like Pasadena), typically design for three (or more) days of self-sufficiency (or autonomy, as they put it).  For our typical, 25 kWh/day home, that would require storage of a minimum of 75 kWh.  But according to Tesla, you can only stack a maximum of nine Powerwall units, which limits you to 63 kWh.  Sometime around noon on that third day without sun, your house will shut down.  Oh, and that much storage will cost you $27,000.

What about the solar array side of the equation?  Let’s start by asking how big an array can you fit on an average house?  House sizes have trended bigger in the past couple of decades, so more recently built houses are an overstatement of the average house out there.  Still, to have a starting point (and to give Musk the benefit of the doubt), let’s assume that our average house is 2,400 square feet (a fair estimate based on US Census data), and that it is optimally designed to maximize solar production: a near perfect square with a true south face, pitched at latitude (34° here in Pasadena), with no shading.  Of course, we still have to give the Fire Marshall the desired setoffs so that gets us to 1,115 square feet of roof space (math available upon request), enough for 62 LG 305 solar modules, but because we need to use a hybrid inverter with fixed string sizes, we will drop that down to 60 solar modules. That yields an 18.3 kW system which at $3.50/Watt would cost a cool $64,000 - and be bigger than our biggest ever residential installation. 

So the Sixty-four Thousand Dollar question becomes: How well will that do on meeting our needs?  Per the CSI calculator, this maximal system will produce roughly 29,000 kWh in Year 1, or an average daily output of 79.5 kWh.  (Less in the winter, of course, when you are most likely to see those cloudy days.)  After providing for my daily needs of 25 kWh, I have 54.5 kWh to spare, not quite enough to fully charge my batteries (which require 63 kWh).  A scenario where I have two cloudy days, followed by one partly sunny day, followed by two more cloudy days could easily leave you in the lurch.  And for this you paid a total of $91,000!  If you live somewhere with poorer weather than what we find in the Run on Sun service area (i.e., pretty much the entire rest of the country!) your performance will be even more dismal.

The true value of storage

The sad part of this whole thing is that battery storage combined with solar is going to be huge, but not for the reasons Musk alluded to in his speech.  The future of utility rates is the shift to time-of-use rate structures - a fact already well and painfully known by our clients in SCE territory, and soon to be seen by everyone.  Time-of-use rates, where utility customers pay more for energy during the peak part of the day, are the only way to match utility costs with customer charges.  (It is the head of the Duck in the famous Duck Curve below.)

The famous duck curve

That “overgeneration” that drives down demand at noon is presently fed back to the grid, where the grid operator has to modify the power mix to accommodate it - in essence, it is wasted.  (Although presently, net metering customers get full retail credit for it - something, that in all likelihood, will soon go away.)

But add storage to the mix, and you shift that overgeneration from the middle of the day, to the evening peak hours, benefiting the time-of-use customer as well as the utility.  It is the way to bring about a peaceful end to the utility-solar wars, and it is the true benefit of storage to solar customers - without oversizing either your solar array or your storage system.

So let’s all get excited over solar with storage, but for the right, and much more cost-effective reasons - and not the nonsensical hype being spewed by that super showman, Elon Musk.

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Comment from: Blake  
4 stars
BlakeGreat article with some very good points. You seem to not like Elon Musk very much and I think that has slanted your article a little but still a great piece. The duck curve and offsetting that massive ramp by reducing the evening peak power is definitely the biggest use for batteries. That being said I tend to be a very literal person. I think your statement from Elon is false but for a different reason. He did not say you could go off grid and run for 3 days without Sun. He did not even say your off grid experience would be remotely similar. He just said you could do it … which is true. The part that was a lie was the 3500 dollar number unless you happen to be one of the distributors they are selling to. I was curious what “TreeHouse” would sell it for but the lowest figure I have heard so far with an inverter is around 7k installed from Solar City.
05/10/15 @ 20:48
Comment from: Jim Jenal - Founder & CEO  
Blake - Actually, I’m a fan of Elon Musk - I think what he has done with Tesla (prior to this) is amazing and Space-X is astounding. But that said, I’m somewhat amazed that the SEC isn’t knocking on his door. As for the literalness of his statement, I think the test is what would the average listener (i.e., potential investor/purchaser) understand his statement to mean. From the gasps of the crowd I suspect they think he means just what I said. The guy is on the SolarCity Board as Chair - he should know what it means to go “off-grid", and he surely knows you cannot do it for $3,500. Either way, the statement is false and I suspect it will come back to haunt him.
05/10/15 @ 23:02
Comment from: Tom Olsen
Tom OlsenI live off the grid and have been doing so for two years. We know that if you dicide to go off the grid doing so means a lifestyle change. We live comfortable on 3kw a day. And where does the author come up with $3.50 a watt for solar. Try $1.00 almost anywhere. By the way, I have $3000 invested so far. I could be interested in a new battery system that will perform better then the “golf cart” batteries I have been using.
05/11/15 @ 03:47
Comment from: Jim Jenal - Founder & CEO  
Hi Tom - Where do you live off-grid? Did you mean you live comfortably on 3 kWh a day? My point was that Musk was speaking to a general audience and implying that they could go off-grid, as they live today, for $3,500 - which is simply not true. As I noted, our average client is using 25 kWh/day - about 8 times what you say you are using, so that would imply a major life-style change. (Which might very well be a good thing, but that is an entirely different discussion!) As for the cost number, $3.50/Watt is inexpensive (to say the least) here in SoCal. And there is nowhere in this country where you can get a solar power system installed professionally for $1/W! Jim
05/11/15 @ 06:33
Comment from: kyle
kyleI can not believe how much Tesla is like Apple was 15 years ago. This here is another example. When Steve Jobs would get on stage, talk up the latest Mac and do his photoshop tests vs the latest PC there would also be articles like this, saying how Steve Jobs was misleading and how other companies already have this or that for less money etc. But it didn’t matter.
05/11/15 @ 10:38
Comment from: jrp  
4 stars
jrpThe three California Investor Owned Utilities (IOUs) prohibit the activation of these units when you are on Net Metering, unless there is a TOTAL power failure from the grid side. So if I get 1 five minute interruption every 3 years….that means I am paying $3k for providing for 5 minutes of power every 3 years? Might have made sense had they been able to design a 120v AC outlet on these units that were isolated from other home wiring…so I could at least use a cord set and charge my plug-in electric vehicle from my solar generated electricity stored in these units…on a DAILY basis and get something in the way of use. I proposed this to SolarCity three years ago when they were offering SGIP battery storage units via a grant from the State of CA….but the response was….crickets.
05/11/15 @ 13:01
Comment from: Jim Jenal - Founder & CEO  
Joel - my understanding was that the IOUs wouldn’t let you charge from the grid and then sell back (i.e., no grid arbitrage) but that they couldn’t prevent you from selling energy from storage that originated on the PV side. Of course, if you are on a TOU rate, and the storage system was smart enough (this is the pitch from Enphase for how their system is supposed to work) you could do away with net metering altogether.
05/11/15 @ 13:07
Comment from: anshul_gupta  
2 stars
anshul_guptaI agree with Blake. Good article, but the slant makes the motives questionable. To point out just a few - 25kW/day is an exaggeration, and you still generate 30-70% of normal on cloudy days. So you won’t run out on noon on day 3 unless you are in a period of a 3-day solar eclipse. There are many others…
05/12/15 @ 15:12
Comment from: Jim Jenal - Founder & CEO  
Anshul - my only motive is to counter the misconceptions fostered by Musk’s speech. 25 kWh/day is by no means an exaggeration in our service area - the vast majority of our clients use significantly more energy than that. I was picking on the low side so as to be more favorable to the argument being advanced by Musk. As for cloudy days, it depends on the degree of cloudiness. A stormy day - not an eclipse - can take you down to 10% of normal yield. A high overcast cloudy day might get to 75%. And then there is the possibility of snow. (Not here in my neck of the woods, but Musk was talking about ice storms, so factoring in snow seems fair - which would make the prediction far worse. Jim
05/12/15 @ 15:26
Comment from: derek_cowburn  
derek_cowburnjrp, Time Of Use billing means the battery can turn off Grid Side during high TOU rates and charge from the grid during low TOU rates. Nothing the utility can do to stop that.
05/12/15 @ 23:03
Comment from: Jim Jenal - Founder & CEO  
Derek - actually you might be surprised at what the utility can do! In particular, they can prohibit the sort of arbitrage of their production that you are (I think) suggesting. jpj
05/12/15 @ 23:44
Comment from: Nathanael
Nathanael25 kwh/day is ridiculously high. What are these, 30-room mansions? More likely they’re houses which aren’t properly insulated. The Super Insulated Retrofit Book, from *1981*, explains how to get your house insulated properly; or you could use the German Passivhaus standards, which are based on the same book. Or maybe the houses are still using incandescent lights instead of LEDs, or something equally stupid. Look at realistic numbers for efficient houses, like 10 kwh/day.
05/13/15 @ 02:49
Comment from: Nathanael
NathanaelIf people in your area – which has no real heating load – are seriously using 25 kwh/day *on average*, you need to send them to energy efficiency specialists before they buy solar panels. It’s just dereliction of duty not to. They’re wasting energy, just wasting it, outright wasting it. That’s the only way to use that much. Unless they all have 30-room mansions.
05/13/15 @ 02:51
Comment from: Jim Jenal - Founder & CEO  
Hi Nathanael - Yes, our typical client is using 25 kWh on average, and that is on the low side. (The 20-room mansion folks are using 200!) Not sure where you live, but such loads are the norm here in SoCal.
05/13/15 @ 06:17
Comment from: BrianK
4 stars
BrianKHi Jim - thoughtful article. We live here in southern BC, Canada totally off-grid. Total cost of our 4.5kWH system was about 6-7 times (installed, with me doing much of the grunt work, electrician doing the connections) what Elon Musk seems to be insinuating as viable for off-grid living. Love the guy, btw, bought his stock some time back (Tesla). Largest item cost in our system is by far the batteries, so if Elon can get his to compete with deep-cycle, lead-acid, then way to go. Only time will tell. For those who disagree with Jim’s customers using 25kWH, bear in mind that most city dwellers are slaves to inefficient mechanical systems housed in inefficient containers. It’s not their fault. It’s what the housing market produces.The largest electrical load for most houses not built on solar principles in the sunny parts of the US and Canada is likely going to be their mechanical cooling systems. Secondly heating, if you use electricity to heat your place. Anything that’s on all day, like A/C, is going to suck back the watts. As Nathaniel points out, Passivhaus is a step in the right direction, but few people have the means or will to build them.
05/13/15 @ 18:23
Comment from: chrishn  
chrishnHi guys, I think 25kWh of energy consumed per day from a single house (how many people in it?) is pretty huge. That would be 9125kWh per year. And anyway, why are you talking just about the 7kWh Powerwall when you want to go off grid? The 10kWh Powerwall should be much more cost effective. I don’t know what the average house is like in the USA because I’ve never been there and I live in south west Germany, an area of average sunny and cloudy days. We have a total of 4 people living in our house and we consume merely 4000kWh per year (no airconditioning here). A Solar panel installation on our roof the size of 10kW(peak Power) would cost us about 15.000 US$ (14.200€), and it would be expected to produce ~10.000kWh per year. So yes, it would be more than enough for us, if we could utilize all of that energy. And so yes, storage is the major issue. Electric energy is quite expensive here in Germany, compared to the US. We pay about 0.35 US$ per kWh when we buy energy from the utility, whereas in the US it’s just about 0.12 US$ per kWh. Meanwhile, if we sell excess solar energy to the utility, we only get 0.11 US$ per kWh. With a given cost of 15.000 US$ for installation of just the solar panels and inverters, adding 3.500$ for a 10kWh storage plus ???$ for installation, it could well be possible that the entire system cost would become cashflow positive much earlier compared to simply relying 100% on the grid. And the main thing to keep in mind is that energy from the grid produces significant amounts of CO2, where as solar power consumed does not. All in all, we’re all human beings, no matter which country or language, and we have just ONE planet Earth, and if this is lost, we all are lost and will pay the ultimate price. There is no plan B. So yes, we all have to put our time, money and effort into conserving our environment, because it is priceless. If you go to the satellite perspective and look at the earth, I feel it basically is comparable to a petri-dish in a laboratory with agar-agar and a bacterial colony on it, which will eventually die suffocating from its own waste (CO2). We cannot let that happen.
05/14/15 @ 04:25
Comment from: bill_southworth  
5 stars
bill_southworthPretty much spot on with your analysis. Elon Musk’s speech has been compared to Steve Jobs. Steve was often guilty of hyperbole and unbridled exhuberance. He had passion for what he had created. Elon Musk’s Powerwall launch was different. It was misleading. I had a customer call me after the launch and tell me if he’d only waited he could have bought a Tesla system for $3,500, that “is exactly the same” as the 60kWH off-grid system we provided for $60,000. Of course, our system is running electric heat, a sauna, and more. It’s a system with no lifestyle compromises and that costs a lot. We owe Tesla a debt of gratitude for validating the market. VCs that thought we were nuts last year now think this is the next big thing. I’m also very encouraged by how savvy the press has been in bringing the emperor’s new clothes under scrutiny. Bloomberg Business (http://www.bloomberg.com/news/articles/2015-05-06/tesla-s-new-battery-doesn-t-work-that-well-with-solar) especially has done a really good job in their analysis. The other thing we’ve learned from Tesla is the need to simplify. We’ve tried to do that with a statistical model correlating a lot of climate, construction, local energy cost, and lifestyle data into a very simple to use calculator. We’re trying to make it better and we’d love to get some more feedback. It’s at http://elecyr.com/solarcalculator. You have a great blog. Keep up the good work.
05/14/15 @ 05:04
Comment from: Jim Jenal - Founder & CEO  
Chrishn - I know it seems shocking to some folks, but trust me, 25 kWh/day is on the low side for our clients. The larger Powerwall is not designed for daily cycling which is why we did not use it in the analysis. But I certainly agree that we need to do more collectively to save ourselves from ourselves. (Oh, and I hope you get to visit the U.S. someday - I’m sure you would find it both appalling and fascinating at the same time! I was lucky enough to visit Germany years ago and loved the people - thanks for commenting!) Jim
05/14/15 @ 06:48
Comment from: Jim Jenal - Founder & CEO  
Bill - Thanks very much for your comment. I feel your pain about your client; part of what motivated me to write the piece was getting lots of inquiries from existing clients about the wonders of the Powerwall (uh, not so much!). Sounds like your client got a very good deal from you! I took a quick look at your calculator - nicely done. (We created a few interactive pieces for our website makeover last year.) One thing - I dialed in 2,400 ft2 for house size and it said that was below average. We used that number in the article because of Census data that picked that value in 2010 for new single-family homes. But overall average would be lower than that, given that average house sizes were around 1,700 ft2 back in the 1970’s. Jim
05/14/15 @ 06:57
Comment from: mark_b_spiegel  
5 stars
mark_b_spiegelContrary to some of the other comments, I actually think that the 25kW/day estimate is deceptively low in the peak of the summer. A central A/C unit alone can draw 4kW and you can easily draw 2kW running everything else in the house. Thus you need to design your off-grid system not just for the annual average consumption, but for July and August during which you may run the A/C 24-7. If you’re averaging 5kw during that time and want 16 hours of power (for when the solar array isn’t producing enough) you’d need 11 Powerwalls (even if the other ten months of the year you could’ve gotten by with fewer).
05/14/15 @ 07:32
Comment from: Jim Jenal - Founder & CEO  
Mark - that is a very good point. At the end of the day, if you aren’t going to change your lifestyle, you have to plan for the worst case - both from lack of solar production (the direction I focused on) as well as meeting that peak need which can be well above average. Thanks for your comment. Jim
05/14/15 @ 07:37
Comment from: Rebekah Hren
Rebekah HrenI’m not sure why there is even an argument going on here that 25kWh a day is high, when the EIA clearly states the US average is 909kWh/month in the U.S. That’s a higher AVERAGE than 25kWh/day. http://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3
05/15/15 @ 07:54
Comment from: Jim Jenal - Founder & CEO  
Excellent point, Rebekah - and I particularly appreciate your providing a link to your source! (And according to that source, Louisiana had the highest at over 41 kWh/day! Yikes!) Jim
05/15/15 @ 08:10
Comment from: boaz  
boazI think there’s some confusion between kWh and kW. Some earlier posters may think you mean a 25kW system is average size, Jim. I assume a 25kWh is 5 or 6kW peak. In fact, national average system size is increasing. In some regions 8kW is becoming standard - we have seen this occurring in AZ in particular. And electrical energy load is most closely tied to cooling, not heating, as one poster implies, and tends to be proportionally higher where cooling is required in a humid environment. That’s why humid, hot states like Louisiana and Mississippi end up with higher daily average household consumption that Arizona.
05/15/15 @ 15:24
Comment from: Jim Jenal - Founder & CEO  
Hi Boaz - about time you joined the party here! You are right, people frequently confuse kW with kWh (made worse by solar companies that use the terms power and energy interchangeably). The all wise and knowledgeable Laurel is hounding me to write a post that explains some of these concepts, and your comment is one more nudge in that direction. Another factor that we see is the problem with older equipment, especially single-speed pool pumps which are still out there in droves. Meanwhile we are working up a proposal for a client who uses 200+ kWh/day and has the bills to prove it! Jim
05/15/15 @ 16:37
Comment from: Boaz
BoazPS - I have lived off the grid for 15 years. Battery is 16.8kW, and considered small by off-grid standards. No cooling, no pool pump, no parasitic loads, no pumps or fans for heating - and I considered my system to offer only about 2 days’ autonomy to 60% DoD. A 7kW or 10kW battery even at 90% DoD, which lithium ion batteries are supposed to provide, could very easily be oversold in terms of the value they offer to a home impacted by an ice storm and consequently without power for a week. A typical forced air heating system would drain such a battery in a few short hours, and a hydronic heating system in a day. Fire up the gennie…
05/15/15 @ 17:06
Comment from: Jim Jenal - Founder & CEO  
How cool is that - someone who has actually done this, offering their insights! I love authenticity! And you see, now that you have gotten into writing comments here it really does become addictive! Jim
05/15/15 @ 17:14
Comment from: ixolabrat  
4 stars
ixolabratI would imagine as storage does become more prevalent in residential or even C&I settings, utilities will eliminate TOU or at least decrease the spread between and take away any possibility of rare arbitrage. Ultimately I see a flat rate irregardless of time.
05/16/15 @ 19:58
Comment from: Jim Jenal - Founder & CEO  
Not sure about phasing out TOU rates anytime soon. To the contrary, that is where we see utilities heading. Storage will have to make significant inroads before I would expect to see that happen. Jim
05/17/15 @ 16:32
Comment from: Bill Southworth
Bill SouthworthOne more fact that seems to be missed in discussions about peak and average power use is that, as homes become more efficient, the ration of peak to average actually increases. We have a project with a HERS rating of 27 before renewable contribution. The home exceeds passive house standards. It’s daily energy consumption is way less than 20kWH but it’s also an all-electric, high end home. The average power is very low, less than one kW. The peak power use is nearly 50 kW.
05/17/15 @ 04:33
Comment from: Jim Jenal - Founder & CEO  
Bill - that is a very good point and it makes me wonder whether we will be seeing utilities instituting demand charges for Residential customers they way they now do with commercial. That would also drive demand for storage… Jim
05/17/15 @ 16:34
Comment from: sagebrush  
2 stars
sagebrushTo continue the flavor of Jim’s article, I have no problem with any of his numbers; in fact, as averages he understate power and energy demands across the US. My objection is to using averages as anything meaningful for this discussion. Joe average has never heard of Tesla, let alone be inclined to be off-grid. Heck, he has never heard of off-grid ! So allow me to frame the question differently, and ask if the Tesla PW is in any way a compelling product for the (current) couple percent of the population who conserve energy, want to reduce emissions, and are willing to tolerate some degree of behavior modification and/or a couple thousand dollars to do so. My opinion for now is: probable, but YMMV My stronger opinion is that the Tesla PW will be much more valuable to people who first learn to conserve energy. Just throwing up 50 PV panels and expecting a single PW to make the utility your new best friend is … naive.
05/18/15 @ 12:18
Comment from: Jim Jenal - Founder & CEO  
Sagebrush - I think the question is more one of perspective - are you focusing on reaction of the “couple percent” audience, or on what Musk’s responsibilities are as the CEO of a publicly-traded company? My focus is on the later, which is why his misstatements - either deliberate or unintentional - are so troubling.
05/18/15 @ 16:24
Comment from: sy_richardson  
5 stars
sy_richardsonHello Jim, Great article and comments, had to read all comments even. With a man like Musk, you need to consider that he thinks in futuristic terms and is probably counting on many advancements such as our energy efficient roofing systems to help his claims become a reality. Our company is introducing a new roofing system that combines insulation on the roof deck(eliminating the traditional thermal mass), BIPV and light weight curb appeal. This new roofing technology dramatically transforms the thermodynamics of the structure making it much more likely that off grid requirements for existing housing stock can be met for the most part. Some applications would require emergency backup generation powered by natural gas, diesel or gasoline. Our energy efficient roof can offset HVAC loads by as much as 70%. Keep the excellent critiques coming.
05/18/15 @ 17:23
Comment from: Paul Coughlin  
Paul CoughlinHaving seen hundreds of bills on both the east and west coast, that number is reasonable. That said, one of the other technological issues with this is inverter sizing. I would love to know what commercially available inverter is going to be capable of starting and running an ac unit. Oh, and at the same time, allow you to cook on an electric stove… And have lights on, T.V., etc. No Way!
05/19/15 @ 11:21
Comment from: Jim Jenal - Founder & CEO  
Paul - exactly! We focused on just one issue - overall capacity/autonomy - but peak power demand, both from the battery and the inverter(s) is an equally significant concern - and one which Musk simply glossed over. Jim
05/19/15 @ 16:11
Comment from: ncbill  
ncbillSorry, I don’t understand your objections. This is an inexpensive, compact, and most importantly standardized way to add expandable storage. Right now, if you want to add storage, every install is essentially reinventing the wheel, e.g. 1. do I go cheap with 6V golf cart batteries (3-5 year lifespan), or 2. pay through the nose for a bulky battery bank built on 2V cells that is still high-maintenance (e.g. power ventilation is needed for hydrogen emitted during frequent equalization charges). Even with the more expensive lead-acid bank you don’t dare cycle it below 50% if you want it to last 10 years - and you won’t be hanging a 20kWh lead-acid battery bank on the wall. It’s also specious to demand that it be able to power a central A/C - off-grid homeowners fire up the generator if they want that, or to use an electric oven, they don’t try to do either with a battery bank! It does allow me to eliminate the half-dozen UPS units I already have, and will run my gas furnace just fine when the ice storm cuts power at 3am (I can hook up a portable generator to recharge it at my leisure the next day).
05/25/15 @ 17:42
Comment from: Jim Jenal - Founder & CEO  
ncbill - I don’t disagree with your comments about what a typical off-grid system owner would/could do. My objection is that isn’t at all what Musk was saying, and as a result, he created a huge set of expectations amongst the public that cannot be met. He didn’t say you would need to supplement your Powerwall with a gas-powered generator, indeed, a big part of his spiel was about getting away from fossil fuels altogether. I am in no way opposed to the concept of the Powerwall, but I am very opposed to people over-promising and then under-delivering. Musk’s comments guarantee precisely that.
05/25/15 @ 17:53
Comment from: Austin  
AustinElon’s statement about living off grid for $3,500 is entirely out of context. His statement wasn’t meant to mean you could go off grid for the price of one powerwall. He simply meant that you could go off grid with a system comprised of solar and powerwall arrays, and then he was revealing the price of a single powerwall.
09/18/15 @ 19:08
Comment from: Jim Jenal - Founder & CEO  
Austin – Well I quoted his statement in full, as you can verify from the video link. The truth is, Elon provided none of the explanation or limitation you are offering. He has to live with what he actually said, not what he (or his lawyers) might wish he had said. Moreover, if he had nuanced his comments as you are suggesting, he would not have garnered the gasps and applause he got from his audience, and he wouldn’t have had tens of thousands of people signing up for what I’m sure *they* think is the chance to go off grid for an extra $3,500. Jim
09/18/15 @ 22:10
Jim Jenal is the Founder & CEO of Run on Sun, Pasadena's premier installer and integrator of top-of-the-line solar power installations.
Run on Sun also offers solar consulting services, working with consumers, utilities, and municipalities to help them make solar power affordable and reliable.

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