I also see that someone forgot to research the inverter clearance requirements. The first inverter is immediately next to the AC panelboard, without the required 8″ spacing. This is an issue for proper inverter ventilation.
I came at this from a different perspective, and went SolarEdge.
1) SolarEdge has one point of failure on the ground where it is accessible, versus multiple points of failure on the roof with Enphase. This was based on my belief that roof optimizers by themselves were more reliable (fewer parts) than inverters.
2) For my particular setup (with no shading other than when it snows), my calculations showed the SolarEdge inverter would come on faster. Your mileage may vary however, and if I had shading I’d look harder at Enphase.
3) SolarEdge’s software was far better and I was able to pinpoint some panels that were not the wattage they should have been (but there software does have areas needing improvement too).
Now, that being said, a month after install I had the SolarEdge inverter go out, and there are burn marks inside the DC cutoff switch. We are yet to hear what that issue was or the resolution, and how SolarEdge deals with it. That is costing me a few days of sunshine and I’m not too happy with SolarEdge at the moment on that score.
Anyway … I’m somewhat non-biased other than having made a decision.
Much needed content on the state of affairs for solar permitting & inspections in LA. Thanks for taking the time to write this. Hope that the county and the other AHJs take further steps to understanding the technology, installation process, and the issues at stake.
Glad to hear that the problems are not acute with Resi at LA County, but in my role with SEAC, I will be addressing both res and non-res, so the issue that prompted this blog post is still of interest to me. Let me know if you would be free to talk via phone so I can be prepared to address your issue next week.
Hi Jeff -
Generally speaking, on resi projects County has only been something of an annoyance (for example, discounting wind tunnel testing results for ballast systems or not excluding live loads from the area beneath the array) but not a major cost factor. For the project described here, the impact was thousands of dollars - a result that neither I nor my client found reasonable.
THe issue of bonding and grounding is indeed a challenging one, has been for years. I too have run into difficulties, most recently on metal shingle roofs where the permitting official required that every metal shingle be bonded to ground. This is impractical/impossible, so I contacted LA County and explained that metal shingles deserve the same consideration as “metal accessories) in section 9.1 of UL 2703 that allows accessories to not be grounded if the system meets 4 requirements #1 non separately derived, #2 points of grounding marked, #3 using listed wire management devices, and #4 sufficient wire management that would prevent conductive components contacting the metal accessories in the event of an accidental fault. After explaining this to the chief electrical inspector, LA county determined that solar could be installed on metal shingle roofs as long as these conditions were met.
There are a number of thorny UL 2703 issues being address by LA County and based upon the review of our Quick Rack system, I feel their review is fair, and their requested supplements, edits, and changes to our listing are perfectly valid. While there will be some bumps along the way, I have found their review fair and reasonable.
I promise to represent your concerns at next weeks SEAC meeting, but would appreciate more specific info on the UL 2703 listing for Everest to better understand why the problems exist with LA county. Feel free to call me at your convenience to discuss.
Hi Jeff -
Nope, I’m not mixed up. LA DWP is the Los Angeles Department of Water & Power and they are the muni for the City of LA. My post is not addressed to them (although they are another whole can of worms).
No, I’m talking about the Los Angeles County Department of Public Works - one and the same entity that has created this SEAC. I agree that this is (potentially) a positive step. My only point was, before they go casting about to identify the causes of PV challenges, they should remove the plank from their own eye!
LA DPW is the municipal utility for LA City not LA County.
The County of Los Angeles Department of Public Works has recently established the Solar Energy Action Committee to address the more vexing issues relating to codes, standards, permitting and inspection for solar installations in cities that fall under LA County’s is attempting to get LA City (DPW) to participate in the Solar Energy Action Committee.
I recently joined SEAC and serve as the representative for the solar manufacturers group. I believe SEAC is a positive step to help bridge the communication gap between building officials and the solar community.
If you have any issues with LA county (not LA City/DPW) please do bring them to me and I will go to work with SEAC to address them.
I like that this is a way to work with the commission but is there a way that we can take this to the Californian people that care about solar as a way to provide cleaner energy?
Is it possible to enable a transition from utility run power line maintenance to solar power company run maintenance? Could solar city and other solar companies bid against the utility company for a specific municipality? This would make the companies compete on service, price and innovation. Imagine a municipal battery bank that allowed for storage for night use. It would reduce the power transmission, loss and more efficiently use the power produced in a city.
By contrast for cities that don’t make these investments they can continue to use traditional means or buy electricity from the neighboring city at market rate. This is to say that there is no loss to these city that chose not to invest in solar.
If there’s an economist out there I’d love to see what the models predict would happen at a macro scale. Would the loss or disruption of the utilities have a negative or positive effect? Would it result in a more efficient use of resources and make the population better off? Could the solar companies actually compete with the utilities?
Thanks, Jeff - but credit for this piece goes to our awesome Projects Coordinator, Laurel Hamilton. You’ll get to meet her at InterSolar next month! (And we will both be needing Battle of the Bands tickets - hint, hint!)
Bravo Jim! I hope more solar installers start following this ethic of advocating re-roofing before solar is installed. The long term cost benefit of starting with a new roof under the array are almost always a great ROI.
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.
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.