Patience
SolarCity scheduled someone to patch the stucco this Tuesday. I'll post some pics after that.[/QUOTE]Thanks!
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Powerwall 2: Installation
- Thread starter JeffreyY
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- Powerwall Tesla Energy
Patience
SolarCity scheduled someone to patch the stucco this Tuesday. I'll post some pics after that.[/QUOTE]Thanks!
I recently received an email from my installer (LA Solar Group and Pick My Solar) indicating, tentatively, that my install would be in September. I don't know whether this is an educated guess on their part, or if they actually have information from Tesla.
I don't have one, but my SolarCity rep was pretty responsive about my installation.
Hengist
Member
I Email the guy who most recently sent me emails about the powerwall. Every couple weeks I ping and get another not very useful response. Clearly Tesla has no clue when install will happen, does not have anything like enough people assigned to manage the existing orders, and does not understand customer service. Good thing my car is better taken care of. This is not yet a market ready product.
Yeah, it seems that way, either that or they're prioritizing the cells for the headline-grabbing industrial installations. Still, as someone that reserved PW1 the day they were announced (on May 29, 2015!), it's not unreasonable to expect better service.
Ulmo
Active Member
Ulmo
Active Member
Anybody have final inspection sign off on their PowerWall 2 installations?
Here's the timeline I have:
I have a feeling that this stuff is new to everyone, so they want to get some really fine tooth combs going through a bunch of unique installations, to set up some generalities that they can use to economize further standard practices and expectations for everyone, so that things can be streamlined in the future. Mostly, I guess this has to do with learning curves by the government and some by Tesla & SolarCity. I don't think they can really generalize very much across all the installations any more than they probably already do; every building is somewhat unique in some way or other. I think most of the learning going on and streamlining to do will be practices around the government understanding the batteries and Tesla installations knowing how to interact smoothly with that. The government has a way of throwing their own learning curves at construction companies and making the construction companies do the learning curves for them, so that's always a bear. I don't begrudge the current processes going on at Tesla & installers over these types of things.
Here's the timeline I have:
- March 15, 2017: SolarCity call saying ready for next step after waiting list. Hit my voicemail due to cell phone no coverage pocket.
- March 16, 2017: I call them back and schedule measurement visit for March 22. Their time from first call to first appointment: 4 workdays.
- March 22, 2017: SolarCity measurement visit.
- ??: PowerWall engineering team called me for questions they had. I do not have an exact date, since my call log doesn't go back that far. It was between March 22 and July 20.
- March 31, 2017: SolarCity first PowerWall Purchase and Home Improvement agreement sent to me to look over. I went back and forth with them for almost a month. This delay can be considered mostly my responsibility as I wanted to learn more about everything. Their time from measurement to first proposal: 7 workdays.
- April 13, 2017: SolarCity final Powerwall Purchase and Home Improvement agreement sent to me to look over and sign
- April 29, 2017: SolarCity Powerwall Purchase and Home Improvement agreement signed
- May 2, 2017: Santa Cruz County Permit for new batteries, issued same day, to SolarCity. Their time from agreement signed to permit issued: <2 workdays.
- June 20, 2017: SolarCity scheduled my installation for July 20. Their time from permit issued to scheduling call: 7 weeks.
- July 20, 2017: SolarCity installation of PowerWall system. Their time from scheduling call to installation date: 1 month (4 weeks 2 days)
- July 21, 2017: SolarCity Tesla Powerwall Payment Reminder. Their time from installation to payment reminder: 1 day.
- ??: SolarCity called me to send someone over to look at the installation. I do not have an exact date, since my call log doesn't go back that far. It was between July 20 and today.
- July 26, 2017: SolarCity Concierge email reminding me of payment. Their time from first payment reminder to second payment reminder: 3 workdays.
- August 3, 2017: Change order for May 2 permit. Not yet approved. Their time from installation to change order: 2 weeks.
- August 11, 2017: I'm inquiring, since I want to pay, but I don't want to pay in full before the installation is totally done (before completed final inspection passes).
I have a feeling that this stuff is new to everyone, so they want to get some really fine tooth combs going through a bunch of unique installations, to set up some generalities that they can use to economize further standard practices and expectations for everyone, so that things can be streamlined in the future. Mostly, I guess this has to do with learning curves by the government and some by Tesla & SolarCity. I don't think they can really generalize very much across all the installations any more than they probably already do; every building is somewhat unique in some way or other. I think most of the learning going on and streamlining to do will be practices around the government understanding the batteries and Tesla installations knowing how to interact smoothly with that. The government has a way of throwing their own learning curves at construction companies and making the construction companies do the learning curves for them, so that's always a bear. I don't begrudge the current processes going on at Tesla & installers over these types of things.
GenSao
Member
GenSao
Member
A quick update on quotes, for my case. Exterior installation with no need for panel upgrade (have existing 200 amp panel) and Solar (5.7 KW System).
1 PW Directly through Tesla = $7,192.50 (Partial Home Backup)
2 PW Directly through Tesla = $13,773.75 (Complete Home Backup)
1 PW Though Swell Energy = $12,334.00 (Too expensive for 1, but at SGIP Step 2)
2 PW Directly through Tesla = $13,773.75 (Complete Home Backup)
1 PW Though Swell Energy = $12,334.00 (Too expensive for 1, but at SGIP Step 2)
I am likely to go with the 2 Powerwalls. If I take the SGIP at Step 3 for Tesla and Fed Tax Credit into account, the payback period is very reasonable (Assuming PG&E EV-A Rate) and provides for a whole house backup. I looked at other vendors, but they are too expensive.
This forum has helped me decide on going with the battery backup though Tesla. Thank you.
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SoundDaTrumpet
Member
I just received my Tesla install quote. Tesla exceeded my expectations because my home did not require the a "main panel upgrade." Few clicks away from submitting my arduous SGIP application for Step 2. Payback period is perfect now.
[Panel jargon: 200A MLO service panel. 175A NEC load calc. 20A PV. Multiple subpanels. PW floor mount 20' away with obstructions.]
[Panel jargon: 200A MLO service panel. 175A NEC load calc. 20A PV. Multiple subpanels. PW floor mount 20' away with obstructions.]
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Ulmo
Active Member
Does anybody with a recent PowerWall 2 install have approximate serial numbers (the first digit after the zeroes and X's to denote how many digits you obscure afterward) of their gateway, PowerWalls, region, and install month? (It's important not to give out anything else, since those may be used as passwords for some internal components or for warrantee replacements.) Such as, mine are:
Gateway serial number ends with 002XXX
PowerWall battery #1 serial number ends with 004XXX
PowerWall battery #2 serial number ends with 004XXX
Region California
Installed July 2017
If you want somewhat more privacy, you can PM me the above approximate data (please no complete serial numbers), and I will summarize here periodically.
I'm asking in order to gauge an approximate progress level on the installs. We know that sometimes these types of numbers are somewhat randomized, but to me, right now, they appear to have some non-random incremental component.
Thank you.
Gateway serial number ends with 002XXX
PowerWall battery #1 serial number ends with 004XXX
PowerWall battery #2 serial number ends with 004XXX
Region California
Installed July 2017
If you want somewhat more privacy, you can PM me the above approximate data (please no complete serial numbers), and I will summarize here periodically.
I'm asking in order to gauge an approximate progress level on the installs. We know that sometimes these types of numbers are somewhat randomized, but to me, right now, they appear to have some non-random incremental component.
Thank you.
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Hi all, this thread has been great, and I'm still not caught up but have read stuff at the beginning (about planning and specs) and end (useful real-world results) and have a few basic questions for you experts out there. Here is some background first.
I am in SF Bay Area on PG&E EV-A and NEM. Located at 3000' in Santa Cruz Mountains near border of 3 counties (Santa Cruz, Santa Clara, San Mateo), with the property just inside Santa Cruz County. I have a 15-kW ground-mount solar array which has offset (over 3 years, but just barely this last year due to harsh winter) all electrical charges, which includes EV charging every night. There is 200A service to house, and at the service entrance I have the wiring coming through an external PG&E meter and then (inside pump shed) a whole-house 200A generator switch and then into a 200A feedthru panel that then goes underground to various subpanels on rest of property. I have an 18kW whole-house propane generator but it is not connected yet to the transfer switch because I've been waiting to decide whether I want to install a propane tank/pad or go with storage battery, or both. So currently we are all-electric and my bias was to see if I can stay that way. My main interest in the Tesla Powerwall is clean backup, since we are on the "last pole" from valley, experience ill-timed blackouts or brownouts, and need power for basic stuff like pumping and pressurizing water, heating water, (possibly running heat pump in extreme weather but this is huge load), and running a couple refrigerators. Although originally able to easily wait out power failures, young kids have changed the equation and apparently they need climate control, working toilets, water, food, etc.
When I sized a potential system on the Tesla Energy site for house size, solar size, and option for full-day backup, it suggests 3 powerwall batteries. This makes some sense since I sized the generator (18kW) at a reasonable subset of critical stuff to run during a power failure, and 3 batteries would give 15kW or 60 some amps at 240V. I do have a lot of basic questions but let me ask just a few pressing ones first:
1) I read somewhere that going from 2 to 3 batteries makes one ineligible for SGIP. Or others have stated it takes one out of residential category to commercial. Could someone point me to the relevant info on this (is there a kW or kWh cutoff? and is one category better than the other for incentives?). Is Fed rebate affected?
2) Any suggestions on # of batteries for whole-house backup in this scenario? Should I try for smaller number of batteries and later try to add propane generator as an extra boost when needed? Is there any agreement by Tesla and installers on how to make the batteries deal with both solar and an external generator??
3) What is the weatherproofing on these things? NEMA 4x?? My solar is perfectly south-facing and adjacent to service entrance. So this is where I would put the batteries. But due to location, area is exposed to the brunt of winter storms from the ocean and we get a walloping and are basically the ridge that shields the valley below us and all the water that dumps here eventually becomes the San Lorenzo river. I can maybe fit one battery in pump shed but it is pretty tight since it also has pumps and power for two water wells and pressure tanks, pressure pumps, etc. Also shed gets pretty hot but shields from water. Ventilation much better outside, but it gets wet in winter, and in summer has some direct sun (I think I can leverage some trees for shade if I install a new pad). My solar has held up well but I over-engineered it with 4'+ concrete footings every 6' feet or so. Also I designed a pod at the top where 6 panels provide shade for the string inverters, and was thinking of another option of mounting powerwalls to that pod next to or behind the inverters. But I'd still need good waterproofing. I've had to battle water infiltration in the inverters but from the wiring that installers did, not the inverters themselves (basically sealing tiny holes between the solar wiring coming out of the inverters to prevent wind-driven rain which basically goes horizontal during storms here).
4) A secondary question is mainly on operation and arbitrage, since I am on EV-A and am pushing the break-even point on solar generation, will probably soon have another EV, and was thinking about using the battery to arbitrage if necessary before end of NEM cycle to help achieve break-even point. If this were the only consideration, it would be more cost-effective perhaps to try to add more solar, but because I have the backup criterion as most important, the arbitrage would be a nice extra supplement.
5) And finally a simple question hopefully. The Powerwall is advertised as going well with solar because it enables your solar system to remain "on-line". I'm confused about how it does this. Simple example: let's say I have just one battery hooked to my 15-kW solar array. At full solar generation and during power failure, would the total installed system actually deliver 15kW to the house, or is it basically wired such that the solar remains "live" but only charges the battery, and then the battery provides power to house at 5kW? If going through the battery, this has some advantages as it stabilizes the power over solar fluctuations, but the trade-off is that it limits the total power to house. Both scenarios need a new transfer switch to de-energize PG&E lines.
Sorry for the long post. From the looks of it, several of you are in Bay Area and I can drive anywhere if you would be willing to show me your system, and be very appreciative and be happy to bring along some of your favorite beverage, etc. I visited several large solar installs in the Santa Cruz mountains before putting mine in and this was very useful.
Thanks for reading!
I am in SF Bay Area on PG&E EV-A and NEM. Located at 3000' in Santa Cruz Mountains near border of 3 counties (Santa Cruz, Santa Clara, San Mateo), with the property just inside Santa Cruz County. I have a 15-kW ground-mount solar array which has offset (over 3 years, but just barely this last year due to harsh winter) all electrical charges, which includes EV charging every night. There is 200A service to house, and at the service entrance I have the wiring coming through an external PG&E meter and then (inside pump shed) a whole-house 200A generator switch and then into a 200A feedthru panel that then goes underground to various subpanels on rest of property. I have an 18kW whole-house propane generator but it is not connected yet to the transfer switch because I've been waiting to decide whether I want to install a propane tank/pad or go with storage battery, or both. So currently we are all-electric and my bias was to see if I can stay that way. My main interest in the Tesla Powerwall is clean backup, since we are on the "last pole" from valley, experience ill-timed blackouts or brownouts, and need power for basic stuff like pumping and pressurizing water, heating water, (possibly running heat pump in extreme weather but this is huge load), and running a couple refrigerators. Although originally able to easily wait out power failures, young kids have changed the equation and apparently they need climate control, working toilets, water, food, etc.
When I sized a potential system on the Tesla Energy site for house size, solar size, and option for full-day backup, it suggests 3 powerwall batteries. This makes some sense since I sized the generator (18kW) at a reasonable subset of critical stuff to run during a power failure, and 3 batteries would give 15kW or 60 some amps at 240V. I do have a lot of basic questions but let me ask just a few pressing ones first:
1) I read somewhere that going from 2 to 3 batteries makes one ineligible for SGIP. Or others have stated it takes one out of residential category to commercial. Could someone point me to the relevant info on this (is there a kW or kWh cutoff? and is one category better than the other for incentives?). Is Fed rebate affected?
2) Any suggestions on # of batteries for whole-house backup in this scenario? Should I try for smaller number of batteries and later try to add propane generator as an extra boost when needed? Is there any agreement by Tesla and installers on how to make the batteries deal with both solar and an external generator??
3) What is the weatherproofing on these things? NEMA 4x?? My solar is perfectly south-facing and adjacent to service entrance. So this is where I would put the batteries. But due to location, area is exposed to the brunt of winter storms from the ocean and we get a walloping and are basically the ridge that shields the valley below us and all the water that dumps here eventually becomes the San Lorenzo river. I can maybe fit one battery in pump shed but it is pretty tight since it also has pumps and power for two water wells and pressure tanks, pressure pumps, etc. Also shed gets pretty hot but shields from water. Ventilation much better outside, but it gets wet in winter, and in summer has some direct sun (I think I can leverage some trees for shade if I install a new pad). My solar has held up well but I over-engineered it with 4'+ concrete footings every 6' feet or so. Also I designed a pod at the top where 6 panels provide shade for the string inverters, and was thinking of another option of mounting powerwalls to that pod next to or behind the inverters. But I'd still need good waterproofing. I've had to battle water infiltration in the inverters but from the wiring that installers did, not the inverters themselves (basically sealing tiny holes between the solar wiring coming out of the inverters to prevent wind-driven rain which basically goes horizontal during storms here).
4) A secondary question is mainly on operation and arbitrage, since I am on EV-A and am pushing the break-even point on solar generation, will probably soon have another EV, and was thinking about using the battery to arbitrage if necessary before end of NEM cycle to help achieve break-even point. If this were the only consideration, it would be more cost-effective perhaps to try to add more solar, but because I have the backup criterion as most important, the arbitrage would be a nice extra supplement.
5) And finally a simple question hopefully. The Powerwall is advertised as going well with solar because it enables your solar system to remain "on-line". I'm confused about how it does this. Simple example: let's say I have just one battery hooked to my 15-kW solar array. At full solar generation and during power failure, would the total installed system actually deliver 15kW to the house, or is it basically wired such that the solar remains "live" but only charges the battery, and then the battery provides power to house at 5kW? If going through the battery, this has some advantages as it stabilizes the power over solar fluctuations, but the trade-off is that it limits the total power to house. Both scenarios need a new transfer switch to de-energize PG&E lines.
Sorry for the long post. From the looks of it, several of you are in Bay Area and I can drive anywhere if you would be willing to show me your system, and be very appreciative and be happy to bring along some of your favorite beverage, etc. I visited several large solar installs in the Santa Cruz mountains before putting mine in and this was very useful.
Thanks for reading!
Ulmo
Active Member
From my experience, PowerWall 2 in enough quantity to cover the connected subpanels would help greatly with this. I've tested by doing blackout cut-off from PG&E (just throw the PG&E breaker); I never tried brown-outs. Black outs operated seamlessly; nothing affected. We have all sorts of regular sensitive equipment that would have been affected were it not seamless.
Refrigerators and water well pumps would stay on battery. Climate control becomes questionable; I'd say maybe, maybe not, depending on your needs, budget, and their overall efficiency. If it had zone flexibility, climate control could be partially backed up. I'm not an expert in this; we have temperate cool climate here near the beach. I think it would depend how many PowerWalls you end up getting and your usual backup needs.
That sounds reasonable in terms of 15kW. Three PW2's is about 42kWh-43kWh of backup when new (and falling over time as it ages, like their cars). My 10kW is more than enough for our modest needs during summer, but in winter, I fear we will be bumping up against that when everything is on. I plan to expand the number of batteries in the future. I had them installed in such a way future expansion is a cinch, except for the money to buy them, of course. I think the key is to size them so the kW covers the fundamental stuff you want all day long no matter what. What panels you back up becomes the question.
I'll await others answering this question. There is definitely a conversion of welfare between 2 and 3 batteries; it's why I selected 2 instead of 3 or 4. You'd need to run the exact options for your situation, of course. Lots of variables. I'm running into the problem I wish I had more solar and batteries for vanity right now while family visits: I'm no longer 100% solar. Our grid power isn't nonoperational enough for me to want more kWh grid backup. You have triple the solar I do; if these PW2's were very cheap, I'd suggest looking at 6 of them as a nice round starting point. They aren't that cheap. After you provide enough for your kW, you're looking at your kWh, and I'd say just do what is affordable for the kWh aspect of it. So, figure out what you can afford, see if you have enough backup panels covered by that kW for the essentials (food, water, shower, toilet, probably hot water, and maybe climate), and see where you're at.
This is an excellent question to talk to the Tesla PowerWall 2 installation engineering team about. You should get this question in now while there is still a little more access to them; when it's been fully consumerized, you may find it is too difficult to figure out.
I don't have a lot of insight into this. My PW2's are suspiciously open-air ventilation cooled. Your general inquiry and approach to this seems correct, i.e., I would continue to inquire about PW2's water handling. I definitely know what you're referring to as your weather situation, and it is real. Once again, I'm many miles from you, so totally different weather, and totally calm winters, under an awning, away from most harm (to anybody not from this region, our region has just microclimates). My hunch is that you'd want your PowerWalls inside your garage, pump room (expanded?), or new shed under the solar panels, but nothing extravagant enough to require huge investment; is there such a thing as a cheap shed that doesn't blow away, with just a few stakes or something? I doubt it.
No, no, that hunch seems wrong as I sit here and mull it over. I have come up with a far better possibility:
The total kW done by the PW2 allows the conduit and wire sizing to be not too obscene; our PW Gateway is literally 45 feet conduit-wise from my PW2's, 1" steel. Our solar feed is 3/4" steel (5.6kWp) for a hundred feet to the inverters; I can imagine your 15kW system being not too obscene. When Tesla's PW2 installer came (in my case Solar City, very competent in my case), they moved my solar feed from the grid panel to the backed up panel. What this means is your solar feed and your PW2 feed needs to go to your backed up panels anyway. One of your backed up panels might be the ideal place to put the PW2 breakers, PW2's, and gateway, plus or minus, depending on what Tesla Engineering says. In that case, I'd be totally not surprised to hear you/they arrange for the solar connection to also end up there at the same or similar spot. 15kW or so for the PW2's, like I said, was only 1" conduit in my 45 foot run; how far away is yours? This could be cheap and easy with respect to weather with new conduit runs to the right spots. You could just put your 6 or 8 or 2 or PW2's inside someplace. I would never put heavy explosive electronic batteries in air breathing space, though, so it should vent as any electric car would vent; ICE cars are worse, so usually garages are perfect. I would be fastidious about proper fire protection wherever the PW2's end up, since they are a store of energy. One fire I witnessed in a laundry room ended up with the building burned 100% to the ground, except for one spot. The only place in that building left standing 100% intact was the boiler room. You see, the boilers usually start fires, but this time, it was a dryer. Well, the double 5/8" sheetrock in the boiler room was enough to not let the fire in that room. They even re-used the same fire-scorched boilers for the temporary laundry room! (They were working fine.) Fire resistance does change the probability and timeline of fire spreading. I made sure I spec'd this out for our PW2's; that's why they're on the furthest stucco wall, sitting on concrete. Unfortunately, they are near garbage bins and under a wooden awning, so there will be some burnables near by. Someday I might want to install sprinkler system right there just to put out garbage fires.
Unknown. Obviously, a huge issue, with lots of swirling angles. Lots of people looking into it from all sectors. Some sectors include foot dragging, and others are supply constrained, so this will be a slow moving target so far, but in the order of years to answer. It will have at least some answers soonish (years), but unknown what level of answers.
So, here's what I'm thinking: when Tesla improves the PW2 gateway software, we'll have some options, which might include:
- Only charge your car using non-peak rate electricity. I can see the software giving declining demerits as follows:
- Dirty expensive utility energy most demerited.
- Clean expensive utility energy demerited almost as much.
- Battery use that would put you in danger of using expensive or dirty utility would be demerited; the multiple conversion losses and cycle losses would put this high on the list.
- Battery use would be less demerited, due to the losses. You want arbitrage, so this would go down to #6.
- Dirty cheap utility energy would next be demerited. You wanted arbitrage, so in your case, this would be #4.
- Clean cheap utility energy would next be demerited. You want arbitrage, so this would be #5.
- Solar power would be the least demerited, i.e., the most desirable to use, for charging the cars, unless it puts you in danger of hitting the other demerits. The predicting the future part is where you have to give it some hints, and perhaps AI comes in.
- I essentially see PW2 controls becoming (low capacity) AI computers in the not too distant future, as in, within 24 months, if Elon is paying any damn attention, which I think he's not (too many rockets and zippy doo dah cars, trucks, and hypertubes). I hope someone clues him in on this soon, because he owns OpenAI, and self-driving cars, and etc. etc. etc., so this should be an easy slot-in for him.
That transfer switch is called the Gateway, and is part of the PW2 install. Edit: I just saw the label right now, and it is a Tesla product, and called a "Backup Gateway", but I believe it is much more than that.
I believe the answer is the good answer: you get solar + battery. I want to test it someday. The Gateway is definitely smart enough to do this, and I believe even in these early stages of software development, it already has that ability. I think I'm fully configured for that now. Do you want me to test it? Of course you do. I have to wait until it's really sunny outside; here by the beach, it takes a while to burn off the clouds. Edit: I just tested, and everything is consistent with the YES answer, which is what I expected. This product has given me a lot of confidence, and it's not one of those things like the Model S where I get in and it doesn't have auto seat positioning as I get in. It just works with this Gateway. Here's the graph and screenshot of the test:
A better test would be much more solar and much more use. 5kW is the regular and 7kW is the peak of my PW2's *2=10kW regular 14kW peak, so a good test would be 5kW sun with about 15kW use. Also, I could turn one battery off and re-test with only 5kW available.
Sure. I could even email you photos of everything, with covers on and off, as much as I can do. That might be more useful to you. I don't want to make that public, because I'm still waiting for the final. I just tried to do a video. About 10 minutes in, I realized a number of things: the video stopped recording after 2 seconds, a full length video describing the whole thing would take 30 minutes, probably a few gigabytes, and I need to unscrew a bunch of covers to really show what's inside. If you PM me your mailing address, I could mail you a DVD with the video. My schedule just went from empty to full; I'm unavailable Monday-Friday until the late afternoon and evening, and should be free weekends, if you want a walkthrough in person. I think looking at more than one install would be helpful, too, since every install is potentially slightly different this early in the installed base.
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@Musterion - You asked a lot of good questions. I will give my opinion on just a couple.
Solar and PowerWall sizing - it is not that clear how the PowerWalls will operate when the grid is down and your solar has the capability of generating more power than what the batteries can absorb. Let's say that you had a power outage overnight which partially drained the batteries. You have two PowerWalls and the solar output is increasing in the morning. While the solar output is small and the household demand is modest, the PowerWalls will have no problem balancing the system - they will discharge to supply any solar shortfall to supply your house and when the solar exceeds the household load, it will charge the batteries to absorb the surplus. Let's say the PowerWalls can charge at 3kW each (I don't know for sure the real number). When your solar generation minus your household use exceeds 6kW, what will happen? Will the PowerWalls be able to signal your inverters to partially curtail their output? Or, will they only be able to shut them down to prevent instability? How graceful will this be? I don't know. However, if you got 3 PowerWalls you would have this problem less often and they could support more of your loads during outages.
Generator backup and integration - I have not seen any information about how or if Tesla can integrate a generator into their system. It seems problematic to me due to their architecture and the way most generators work. Other systems that are designed for off-grid handle generators in an obvious and elegant way.
Solar and PowerWall sizing - it is not that clear how the PowerWalls will operate when the grid is down and your solar has the capability of generating more power than what the batteries can absorb. Let's say that you had a power outage overnight which partially drained the batteries. You have two PowerWalls and the solar output is increasing in the morning. While the solar output is small and the household demand is modest, the PowerWalls will have no problem balancing the system - they will discharge to supply any solar shortfall to supply your house and when the solar exceeds the household load, it will charge the batteries to absorb the surplus. Let's say the PowerWalls can charge at 3kW each (I don't know for sure the real number). When your solar generation minus your household use exceeds 6kW, what will happen? Will the PowerWalls be able to signal your inverters to partially curtail their output? Or, will they only be able to shut them down to prevent instability? How graceful will this be? I don't know. However, if you got 3 PowerWalls you would have this problem less often and they could support more of your loads during outages.
Generator backup and integration - I have not seen any information about how or if Tesla can integrate a generator into their system. It seems problematic to me due to their architecture and the way most generators work. Other systems that are designed for off-grid handle generators in an obvious and elegant way.
Based on the exchanges I had with Tesla, when they were trying to push me to 3 PowerWalls, the answer is you will get zero charging and the PV system will get shut down if the PowerWalls cannot absorb it all. According to the specifications a PowerWall can charge at 5kW, so a pair can take 10kW of surplus. I think that is a pretty large number and most systems would be hard pressed to produce that much in excess (no loads in the house). I suspect if there are no loads you probably don't care anyway.
For those keeping score, I'm still hoping Tesla can fix the screw up with them failing to submit my SGIP (they seem to have small gap between what is submitted and the per vendor cap) or waiting for step 3 or I find another vendor.
arnold
So, if the system was not charging due to excess production and you were home and you knew what was going on, you could just turn off or flip the breakers for some of your inverters during the excess production hours of the day.
Ulmo
Active Member
It seems to me inverter manufacturers will want their systems to function well with batteries. If they want to get anti-competitive with this, they're basically saying they want to roll their own battery products in competition and no compatibility (lock-in) for items that are a major portion of a home's cost; I don't see that working out. This should be smoothed out, and sooner for those companies that want their products to be sold more. We already know that inverters can invert less when they have less input. @wk057 's system will invert less every day when he isn't using it (see wk057.solar). There's not much technical reason why they wouldn't handle this situation; just policy decisions by Tesla, SolarEdge, SMA, Enphase, etc. Although, I do remember Jason talking about a sink load if he couldn't find a way to turn down the inverters (which he quickly decided wasn't his path).
I could run this test when I have permission from everyone in the house: turn off all but one of my PW2's (I believe one switch); disconnect PG&E (one breaker); try to time this when the battery will get full from solar power; see what happens. This test would have been easier during summer when it was sunny. I could shoot for this weekend when I'm home during the day.
