Blog Post from a Solar Power Installer (my alternate title: How the Non-Tesla Faithful view the PowerWall):
Elon Musk's 3-Biggest Powerwall Whoppers
Elon Musk's 3-Biggest Powerwall Whoppers
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Elon Musk's 3-Biggest Powerwall Whoppers
- Thread starter woof
- Start date
Jim Jenal knows what he is talking about, and I agree with what he wrote. Elon's presentation wouldn't have been bad if Tesla had followed up with technical info and white papers, but they didn't (that half a sheet spec sheet doesn't count).
If Tesla were any other company, I too would be shouting Vaporware! But this is classic Elon. Put together a solid solid solution and then announce it before the engineering, product management, sales, marketing, business development and tech support teams within the company have barely started their work.
I do think these energy systems products will be good, but it'll just take a while for Tesla to sell them properly.
In the meanwhile, what Jim wrote in his blog post is spot on.
If Tesla were any other company, I too would be shouting Vaporware! But this is classic Elon. Put together a solid solid solution and then announce it before the engineering, product management, sales, marketing, business development and tech support teams within the company have barely started their work.
I do think these energy systems products will be good, but it'll just take a while for Tesla to sell them properly.
In the meanwhile, what Jim wrote in his blog post is spot on.
It was a pretty good article but he clearly has a bone to pick with Elon. I dont think anyone involved in Tesla Energy or Solar City has any doubt that the biggest use of these batteries will be "taking the head off the duck". I think Utilities could still come out of these in good shape if they play their cards right. I also think that Powerwall will actually improve the way utilities treat customers in the longer term. If HECO continues to delay solar installations from hook up for 18 months and a substantial amount of people go off grid it will be a true wakeup calls to Utilities everywhere.
With the price of Electricity going up and battery/solar prices going down it will only be a matter of time till people can go off grid for around the same price as being on grid. Hopefully policy going forward will be better than it has been in cases like the Arizona SRP demand charges on solar users only.
With the price of Electricity going up and battery/solar prices going down it will only be a matter of time till people can go off grid for around the same price as being on grid. Hopefully policy going forward will be better than it has been in cases like the Arizona SRP demand charges on solar users only.
Great article. The only nit I would pick is that the 10kWh packs should be what you buy if you're looking for stand-by generation; he seems to use the 7kWh pack for all purposes. Changing this nit doesn't affect his argument or conclusion in any meaningful way.
Jenal's estimates for average home energy usage are ridiculously high. Especially for Pasadena, where he is, which has no significant heating load, and where the houses are generally new enough that they aren't single-wall masonry. There is no way anyone except huge mansion owners should have energy usage nearly as high as 25 kwh/day.
I conclude that he's probably routinely committing an act of professional malpractice, selling people solar panels without first selling them much cheaper and much more effective energy-efficiency improvements. I notice that unlike many other solar installers, he *doesn't* have an energy efficiency section on his website.
Redoing all the numbers with *realistic* energy usage levels kind of trashes his conclusion. Musk is still overselling a bit (most people will need two Powerwall units), but not much.
I conclude that he's probably routinely committing an act of professional malpractice, selling people solar panels without first selling them much cheaper and much more effective energy-efficiency improvements. I notice that unlike many other solar installers, he *doesn't* have an energy efficiency section on his website.
Redoing all the numbers with *realistic* energy usage levels kind of trashes his conclusion. Musk is still overselling a bit (most people will need two Powerwall units), but not much.
Many "normal" sized homes use as much as 25kWh per day especially when AC is used during the summer.
We use a around 40kWh on an average day without AC. A little over half is the Tesla and Volt charging, but the that still leave almost 20kWh per day. And we have a fairly efficient house with 100% LED lighting and modern appliances.
Our "baseline" usage (when no one if home) is around 0.5kWh, which is 12kWh per day. That includes the refrigerator/freezer, wifi, internet, wine fridge, TiVo, and all the normal things in a modern house.
Last edited:
AC in hot climate.
Electric heat.
Either of those could push any sizable home onto 25kWh/day.
In fact, given that buyers would be affluent, you could easily argue that you'd expect them to have higher than average usage, and especially so if they own a Model S.
(Incidentally, our average for the year to March 2009 was almost exactly 24kWh/day and I'd _already_ reduced it a bit through efficiency savings after having moved in with my wife and family in 2007. Neither electric heat nor heavy AC use. I've knocked it down by 1/3, excluding charging the Volt. We'll now drop around another 1kWh/day due to last weekend's passing of a bearded dragon.)
The biggest limitation of Powerwall is, I feel, the 2kW power. The greatest strength is that it's got a price and warranty out into the public consciousness, which could help start cleaning up the market and eliminating some of the weaker efforts, while also helping it grow. I think Tesla's done the market a great favor with PowerWall's limitations.
Last edited:
Average energy use, and what you should reasonably using in a power outage are two different things. I've only got a 2kW generator for use in power outages, and its only that high because of the startup load on the fridge. Personally I would perfer a refillable generator in a power outage to a battery of any reasonable size, however if you're in an area with less stable power where you frequently have outages for a couple of hours it seems like a great solution.
This guy clearly has a bone to pick with Elon, which of course makes sense since his company is a direct competitor with Solar City. Most of his conclusions aren't really wrong, but he blows them way out of proportion by making exaggerated assumptions. (like using the 7kW unit instead of the 10kW as a backup)
This guy clearly has a bone to pick with Elon, which of course makes sense since his company is a direct competitor with Solar City. Most of his conclusions aren't really wrong, but he blows them way out of proportion by making exaggerated assumptions. (like using the 7kW unit instead of the 10kW as a backup)
JimmyAZ
Member
I wish he had quoted more efficient panels. We have a 21kW system on our roof - 40 panels, made by SunPower. They put out 345W rather than the 240W with is the norm. I can't imagine another 20+ panels and not getting the same efficiency!
JimmyAZ
Member
Hey that's a good point. Math is no longer my strong suit. And this solar is new to me. I think I confused something. I just pulled up the lease agreement and here's what it says:
40 panels, 13,8kW DC, 11.4kW AC
Year 1 production estimate - 22,348 kWh
So when people are discussing the size of their solar setup, they're talking about the total kW of the panel count * wattage of the panels?
I've been telling people the kWh value. Geez I feel naive now. My apologies for the err and thank you for getting me to figure out the truth.
I'm just glad you actually got what you were sold. :wink:
I happen to be considering using those panels myself, and might be able to squeeze an ~18KW array on my roof with 53 panels, so your numbers stood out to me.
I'm beginning to suspect my neighbor may have been sold something "optimistic" or he's mistaken about his installation ...:frown:
- - - Updated - - -
Oh and incidentally, that larger annual value is ~22 megawatts!
Skotty
2014 S P85 | 2023 F-150L
Our house in Missouri is around 3000 sq ft, built in the 1990s. Sort of big for the midwest, but not rich folk big. We haven't taken any big measures to improve efficiency so far, just improving as we go. A mix of LED, CFL, and incandescent lights, average insulation, average windows. Our usage is almost exactly the same as Twiglett. The low over the last year was 34.5 kWh / day and the high in mid summer was 77.5 kWh / day. I know it could be improved, I just don't know how much. But it makes a good example of a typical house of the size.
We don't have a Tesla, but we do have a Volt, so that adds to it a little.
Despite this, I would still find a 10 kWh PowerWall to be useful for backup. I'd be happy if it could just power the refrigerator, sump pump, a few lights, with a little to spare for something else. I'm not sure how long it would last, but if it could handle that load for several hours, that would be awesome. Right now I've got a UPS that was around $350 and it can power my PC and nothing else for about 10-15 min before going offline. It also claims to need a new battery every 2-3 years. Compared to that, I'd say the PowerWall at $3500 sounds pretty darn good.
Last edited:
cschock
Member
We have a 3400 sq ft house and our average consumption per day over the last year was 41 KWh, including charging our Model S for average use of 50 miles per day! However, we have a newer house with now mostly LED lighting, gas dryer/cooktop/heat/on demand water heater so that knocks off a lot of electric use in what may be a more typical home. There are so many variables in discussions like these. If we didn't have the Model S our solar array would be massively over sized (and I'd probably be looking into converting the gas dryer and water heaters to electric!)
