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.
Sorry, 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).
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
Having 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!
SageBrush - You say their reliability record is spotty, but that hasn’t been our experience at all. In fact we have dozens of SMA inverters in the field and thousands of Enphase microinverters. We have replaced the same number of each type of inverter - four. (Our earliest SMA install is 2007, our earliest Enphase install is 2009.)
As to the second point, I don’t know of anyone charging their EV via DC - while you could do it that way, that’s not how the overwhelming number of EV chargers are configured - so that idea is not really relevant to how people use these things.
Assuming Enphase can deliver on their storage product later this year, you will have a truly AC-integrated solution.
Two reasons would tempt me away from Enphase these days:
1. Their reliability record is spotty. While the hardware is warrantied for a long time, labor is not included.
2. I like the idea of a DC system that can feed DC appliances like a Tesla PW or an *EV and only shunt what is needed to the inverter.
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.
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.
To 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.
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…
One 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.
I 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.
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!
PS - 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…
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!
I 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.
I’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
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
Contrary 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).
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.
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!)
Pretty 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 $60,000. Of course, our system is running electric heat, a sauna, and more. It’s a system with no lifestyle compromises and that costs a lot.
We owe Tesla a debt of gratitude for validating the market. VCs that thought we were nuts last year now think this is the next big thing. I’m also very encouraged by how savvy the press has been in bringing the emperor’s new clothes under scrutiny. Bloomberg Business (http://www.bloomberg.com/news/articles/2015-05-06/tesla-s-new-battery-doesn-t-work-that-well-with-solar) especially has done a really good job in their analysis.
The other thing we’ve learned from Tesla is the need to simplify. We’ve tried to do that with a statistical model correlating a lot of climate, construction, local energy cost, and lifestyle data into a very simple to use calculator. We’re trying to make it better and we’d love to get some more feedback. It’s at http://elecyr.com/solarcalculator.
You have a great blog. Keep up the good work.
I think 25kWh of energy consumed per day from a single house (how many people in it?) is pretty huge. That would be 9125kWh per year.
And anyway, why are you talking just about the 7kWh Powerwall when you want to go off grid? The 10kWh Powerwall should be much more cost effective.
I don’t know what the average house is like in the USA because I’ve never been there and I live in south west Germany, an area of average sunny and cloudy days. We have a total of 4 people living in our house and we consume merely 4000kWh per year (no airconditioning here). A Solar panel installation on our roof the size of 10kW(peak Power) would cost us about 15.000 US$ (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.
Hi 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.
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.
If 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.
25 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.
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.
I 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…
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.
The 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.
I 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.
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!
I 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.
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.
Great 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.
Hi Chris -
I agree that installers need to make their voices heard with their Representatives in Congress as the end of the ITC is a very big deal. Keep in mind that this is worse for the smaller installers because we don’t install residential projects as “commercial” installs (since we don’t own the systems and bill consumers through a lease or PPA). The folks that do that will still be able to claim 10%, but our residential clients will get nothing. When the ITC was expanded, I’m pretty sure that Congress never contemplated that a system on someone’s home would be counted as a “commercial” system for purposes of the ITC.
You raise two points with differing degrees of concern: 1) how to enforce a performance warranty, and 2) what to do when you have a defective product with no warranty support available. Let’s take those one at a time…
As to the first point, the short answer is you cannot. We tell prospective clients to think of the performance warranty as an aspirational statement: based on the manufacturer’s testing, they believe their product will produce X% of nameplate energy, 25 years from now. Consumers simply do not have the technical resources required to make a claim against such a warranty except in extreme cases (i.e., the panel ceases power production altogether). The good news is that quality products will hit those figures. But beware second-tier (or worse) products - if the deal is too good to begin with, it is far more likely to be a bad deal down the road.
For the industry as a whole, the second point is far more of a concern - what to do with string inverter systems when a single solar panel in a string has failed? As the industry moves forward, there are few, if any, “legacy” panels available, even if the manufacturer is still in business. If you switch to a panel by another manufacturer that more or less matches the performance characteristics of the other panels in the string, the physical footprint may well have changed meaning that the placement of that panel into the existing racking system may require juggling a multitude of other panels so as to place the replacement on a corner where it may fit. This problem becomes notably worse if the mounting scheme depended on a proprietary mounting method, such as the Zep mounting system that is popular in some quarters today. What happens if 10 years from now no one is making Zep-enabled panels?
As an industry we talk about 25-year systems - indeed that is a selling point in most cases - but many aren’t designing systems that are not only strong enough, but flexible enough to last through some inevitable changes. As you note, microinverters are a big step in the right direction, but that is little comfort to folks having problems with 10-year old string inverter systems.
As to your legal question - there is indeed a law in CA regarding shading of an array by a neighbor’s later-planted trees and foliage. It is known as the Solar Shade Act and it provides limited assistance for solar power system owners. You can read an overview of the law here: http://www.sandiego.edu/documents/epic/100329_SSCA_Final_000.pdf
The 2016 sunset of the 30% solar ITC will be a death knell to many solar installers. Hundreds of thousands of jobs that have been create will go away overnight. It has more than paid for itself in economic activity, but the forces of the fossil fuel industry are lined up against it.
We all need to hammer our congressmen to support Obama’s recent 2016 budget proposal that extends this credit permananently. If they are not called to give a logical reason for their support of killing this, they will be let off the hook.
A point well taken. As more and more Solar Manufactures go out of business or become absorbed by other larger companies: what happens to the warrantys?
How do we as homeowners go about proving that our system is not living upto the warranty?
1000/Wm2 is easily the average on any full sunny day at 2PM in August since we should be between 1500 to 1700 W/M2 in LA.
Pull out each module in the string and take measurements.
If say we find 1 out of 4 are under said warranty how do we go about getting a substitute that will fit the Volts and amps in our older string.
Sure today microinverters will give us individual readings for each module but sting inverters on the over ten year old
Side do not have that luxury.
Hoe do we get refunded by said manufacture even if they are in business?
Please help answer this for the thousands of people that have invested huge amounts of money especially older systems before equipment started to reach grid parity?
Which companies are able to do testing on site of arrays that are 10 years old now. That should according to the warrantys still be able to produce 80% of the original output.
Say for example you have an array Shell 155 watt modules.from 2005!
That is true for any manufacture ten years old BP.
We have two BP 165 modules from that same time frame used for a seperate back up power supply for the Freezer.
Your neighbors trees have now grown ten feet. So they are cutting into the annual average.
I think their is a law governing trees that encroach into a neighbors solar system : that’s another question: is that law in effect in The city or County of LA ??
For get that :
What is the procedure for proving that every module is living up to the manufactures warranty?
Hi Fred -
Thanks for the comment, though the misinformation bit is a tad overstated. I got my information from the SolarEdge website where their video on grounding shows an illustration of running #6 from unit to unit, depending on the AHJ. But I don’t have to do that in any jdx local to us (including City of LA or County of LA) for the Enphase M215IG or the M250. Here’s a link to the video that I’m relying on: https://youtu.be/b13z2bKMQJc?list=PLsgvvbvtreLJdH84sKOYKl3mVVa2DtvbK
Are you an installer? Have you installed these in either of those jurisdictions w/out running #6?
Our typical residential client purchases a 6 kW system for right around $4/Watt (sometimes more, sometimes less - and some clients purchase systems as small as 3 kW, though only in Pasadena). That means a $24,000 price tag. In SCE territory, there are no rebates so the 30% ITC come to $7,200. If you split that over two years, that comes to $3,600 a year, or about the tax you would owe (absent other deductions) with an income of roughly $30,000. So, for most people who can afford to purchase solar, the 30% ITC can be used in two years, and reduces their cost of going solar by a full 30%.
The main problem is that middle class wage earners CANNOT afford the upfront price for Solar or Geothermal without maintaining the current 30% tax credits to carry forward for more than a few years. Middle Class DO NOT make enough money to be paying $10k worth of taxes per year. So this, once again, is for only the higher income tax brackets to utilize as a tax shelter. The wording should be that the 30% tax credit can be carried forward until it is used up!!!!!!!!!!!!!!!!!!!! Then the ability to afford these systems will be opened to the middle class wage earners and THEN this country can work to get to the point where we actually maintain our standard of living plus be using less than 1/3 of the energy we currently expend to do so.
Jim Jenal is the Founder & CEO of Run on Sun, Pasadena's premier installer and integrator of top-of-the-line solar power installations.
In addition, Run on Sun offers solar consulting services, working with consumers, utilities and municipalities to help them make solar power affordable and reliable.