Too many panels for PW2?

Too many panels for PW2?

I have a deposit in for a single PW2, I did all the pics and answered all the questions... after a few months I got my estimate:

4 power walls for $26,869 (whole house backup)
2 power walls for $27,679 (they said they would have to rewire my house)

No one has been to my house to look at anything, this is only from the pics requested that I sent them and the only explanation they could give me was that I have too much solar. I have 9.7k on the roof, and only want a partial backup, 1 PW.

Has anyone else run into the "too much solar" problem for the powerwall? I figured once the battery was charged any excess production would be net metered like it is now. I need someone versed in this to help because the Tesla reps on the phone only read whats on their screen, Im looking for the limitation explanation.

Tesla-David | 18 marzo 2018

Your response concerning the size of the PW2 system required with a 9.7 kWh solar system is very puzzling indeed. I had my PW2 site assessment last month with a 13.2 kWh solar system previously installed in 2012, and am proposing a 2 PW2 backup battery installation, which the Tesla rep doing the assessment agreed with to power my home. Where do you live and what is your average monthly energy demand? I live in Edmonds, WA, and we are averaging around 13-14 kWh/day (5.5 kWh - 28 kWh/day is the range we get at our home on an average year) to power our all electric home. Two PW2's equating to 27 kWh would work to backup our home.

If you go with a 1 PW2 installation, you would be limited to 13.5 kWh in backup storage which should be enough to keep your lights on and refrigerator running, etc. I certainly don't understand the logic that you would have to rewire you home for a 2 PW2 system. You definitely don't have too much solar IMHO. I would request Tesla-Energy send a Tesla rep out to your home for an in depth assessment. I am still waiting to get my estimate and an installation date for my PW2 system.

Captain Ducman | 18 marzo 2018

Thanks David, Im by no means an electrical engineer, but consider myself at least as handy if not handier than the average bear. I don't understand it either and no one will let me talk to the person saying that is what is necessary. Did they do the site assessment before you confirmed your order? Because I only have the two options on the tesla website, neither are appealing. Been dealing with this since Nov '17.

We live ~1mile from the Gulf of Mexico just north of Clearwater FL. Our house uses 1100-1700kwh per month with solar production of ~1100 per mo. We sell back (wholesale) every day the sun is out but buy it back (retail) at night. Looking to power the house at night and in the unlikely event of a hurricane, power the inverters so the solar will charge the PW and power essentials in the house while waiting for the power co to restore service. but our goal is to use the battery daily as opposed to a stand-by generator that only gets used in an emergency.

sashton | 18 marzo 2018

I have had a single PW II running with a 10kWp PV system. I prioritise the PW so that it takes the first 5kW and a "smart" car charger takes the remaining excess. The PW is happy to scale from 0 to 5kW but the car charger will only scale from 1.4kW to 7kw so at the tail of the day the solution is not as clean as it could be. In the winter the car charger has to be set to take a significant portion of its charge from overnight cheap rate power but as the spring comes the proportion of grid based car charge has dropped. Last week 88% of my EV miles were PV supplied. NB I am retired so my weekly average mileage rarely exceeds 100 miles.
The PW has no apparent issue with hitting 100% full and relatively gracefully stopping charging.
So I can see no problem with your single PW solution. Of course, just one would not permit you to reserve much for backup.
I will certainly be buying another PW once the backup gateway becomes available here in the UK.

Captain Ducman | 19 marzo 2018

OK, so a larger PV system IS possible with a single PW is what Im reading here.

Thank You both for responding...

Any others with larger PV systems and a single PW?

Tesla-David | 19 marzo 2018

@Captain Ducman, I got the site Assessment, and at this point nothing is confirmed because I have not received an estimate or proposed plan from Tesla-Energy. I discussed my intentions with the Tesla rep doing the assessment and he agreed with me that a 2 PW2 installation as I proposed seemed to work. I have been trying to get a Powerwall installation for almost three years now, having started with the PW1. It has been one long frustrating process and I have been complaining repeatedly to get some attention here in the Northwest. You need to elevate your concern up to management as you don't appear to be getting any reasonable feedback from your Tesla rep. @sashton's feedback confirmed that your solar system is not too large to accommodate a single PW2. Let us know how this turns out and good luck!

raybentz | 21 aprile 2018

I live in Puerto Rico, and have had a 12kW PV system (without storage) on my roof since early 2015. We've been going along happily net-metering ... then hurricanes IRMA and MARIA came to visit. We lost power at IRMA, and never got it back until mid-February.

The PV system survived the storms without a scratch (which is surprising since the roof blew off my neighbors house, and landed 2 acres away in my yard). Thankfully, when we installed the PV system, we opted for the "secure power supply", which allowed us to pull about 3kW of unconditioned energy off of our system during daylight hours. After living like that for 163 days, we were itching to get a storage solution.

We put a deposit down on a PowerWall 2 about a month ago, and the installation (one PW2 + backup gateway) was completed this past Wednesday.

Our PV system is 48 panels, split into 2 arrays of 24, with each array going into its own inverter (SunnyBoy).

The way they decided to hook it us was to send the AC from 1 inverter (6kW) to the PW, and the leave the other inverter grid-tied. My Backup Gateway only sees the 6kW from the 1 inverter. The other inverter comes into the Gateway on the "grid" terminals ... so those terminals contain a mix of solar and grid energy.

On the first day, the PW charged from 16% (that was the charge out of the box) to 100% within the day, so obviously the 6kW coming from the 1 inverter is enough to feed the PW, my house, and even export back to the grid.

My issue is that, in the case of a grid outage, the second inverter (the one NOT connected to the PW) will shut down, and be of no use to me. My concern is not a short outage (those are part of normal life here in PR). It's with another long-term outage ... I want use of the whole 12kW on my roof during the day. I'm fine cutting my consumption back at night ... but when the sun is shining ...

This set-up was not explained to me beforehand. I was told by the sales rep that I _would_ have full use of the 12kW during the day during an outage ... we're still fighting about that.

Anyway ... the reason I was given for only taking the 6kW from the 1 inverter is because the PW cannot handle the full 12kW. They say ideally the PW wants 6kW to about 9kW .... not sure. I don't fully understand all this stuff yet. But certainly, I'm being told that my PV system is "too much" for the PW.

Tesla-David | 21 aprile 2018

@raybentz, reading your narrative It looks like the solution to take advantage of the full 12 kWh solar array that you have would be to add another PW2. I have a 13.2 kWh solar system and am proposing 2 PW2 system to handle my storage. That is what I am proposing, but am still waiting on the official proposal/plan, which should be forthcoming in a week or so. Glad to hear that you are operational and that your lights are on, but agree with you about wanting the full solar input to your battery storage, not just the 6 kWh you presently have.

bhanuk99 | 30 aprile 2018

I agree Tesla's customer service is not great. I have a 5.4 kWh PV system that was installed by Solar City in 2013. For PW, I put down $500 deposit on Jan 31 2018 and a guy came to do site assessment mostly for the purpose of where the PW would go and clearance. Because Solar City installed the panels they have all my utility usage info. After site assessment I constantly nagged them and they suggested to get 1 PW and mentioned I cannot use my Tesla charger in the event of power failure. I know the limitation of my electricity production by solar energy but my usage is also not that much. I have natural gas for cooking and heating, and also have a gas dryer. I watch my electricity production and usage numbers every single day. I talked to a Tesla energy consultant armed with complete data from my electric use, PV energy generation by day/month/year, and how much allowance my utility company is giving me each month. I told him it is not too difficult to generate something like an excel spread sheet from Tesla's end. He was very nice and sent me detailed data on my consumption and production. We discussed and I decided to get 2 PW because there are many days where I produce lot of electricity but use less and they are sent back to the grid only for my utility company to give me credit for 1/3 of what I produce. by having 2 PWs I can charge my car when I produce 35 kWh in a day but use only 12 kWh without sending to the grid. I may be naive in my thinking and it is possible my utility company may outsmart me. I do have a whole house Generac generator if my power goes out for 3 days or so if and when I use all my PW storage. It makes sense for me to get that extra PW when it does not add more installation costs and there is 30% tax incentive on the total cost of the unit and installation. They have scheduled me for Aug 1-2 installation.

Tesla-David | 30 aprile 2018

@bhanuk99, I have a 13.2 kWh solar system installed in 2012, and currently waiting to get a 2 PW2 installation, but have not gotten an install date yet, but signed our contract last week. I am also keenly interested in charging our two Tesla's (MS & M3) off of the PW2, but recognize the limits of doing that with 2-PW2 batteries. I found this utube presentation useful in describing how to do that with his 2-PW2 installation. We produce more than enough electricity off of our solar roof (~13,000 kWh/year) to run our all electric home (~5,20-0 kWh/year) and charge our two Tesla's (~3,000 kWh/year) in Edmonds, WA.

bhanuk99 | 30 aprile 2018

Thanks @Tesla-David for the you tube link. Very useful. I live just outside Wash DC in the immediate MD suburb. We get a good amount of sun shine.

cwied | 30 aprile 2018

I'm a little surprised that the Powerwalls would shut off when grid-connected. Surely if demand is higher than what the Powerwalls can supply, the extra power could just be pulled from the grid, couldn't it? It would have been interesting to see the supposed "shutdown" occur to confirm that this is the actual behavior.

FloridaDave | 30 aprile 2018

@Captain Ducman - I would contact Caleb Suwak, the Tesla Energy Advisor over at the International Mall in Tampa. He might be able to help you through any issues and questions you are currently having. He helped me with my solar and 2 PW2's before and after hurricane Irma.

Tesla-David | 1 maggio 2018

I am excited, Tesla-Energy (Josh) called yesterday to tell me they have submitted PW2 design to our electrical provider (Snohomish PUD) for approval (3-4 weeks for approval as we are first in Washington State), and that I can expect PW2 installation in June. Finally getting this done.

FloridaDave | 1 maggio 2018

@Tesla-David, you are gonna love them. I've had my system officially turned on for just over 2 months and have been completely self powered day and night at least 95% of the time.A couple of cloudy days in a row caused us to use some grid power, but not much.

bhanuk99 | 1 maggio 2018

@Tesla-David, congrats! I am happy that they can install in a month after the clearance/approval by utility. Tesla submitted my design in early April and Pepco (utility) sent email about a week ago wanting more info. I called Tesla energy last Fri and they said Tesla will resubmit with modifications end of this week or early next week. In spite of that Tesla said the installers could not install before Aug 1-2.

Patrick | 25 giugno 2018

@FloridaDave and @Captain Ducman,

We are located in Tampa Bay as well - Tierra Verde area near St. Pete Beach. Our 14kW solar PV generator was installed over two years ago before the PW2 hit the market. At that time a battery system didn't seem like a priority given our relatively low energy cost and the high grid reliability in this area.

When PW2 hit the market it seemed like a game changer for several reasons, so I'm now doing more research on possible use cases in preparation for installing a few PW2s on this home. Definitely planning to install them on future homes. I'm actually heading down to International Mall today to see the showroom M3 (I'm a reservation holder) and will look for Caleb Suwak - thanks for the referral.

A few quick questions please:

- Are your combined generator/PW2 systems setup to run your entire house load in the event of a grid failure?

- When the grid fails does the combined system work like a "whole-house UPS", automatically switching over to power the house from the inverters and PW2s while grid is down?

- If so, how long does the switch-over really take? I've read posts from early users saying it can be instantaneous, so fast that a PC would not reboot after the switch. Has that been your experience?

- Any chance of getting a look at your systems sometime?

Thanks in advance. I can be reached: patrick at aeropartners dot com or eight one three, three nine zero, seven one zero nine.


Tesla-David | 25 giugno 2018

Reporting back on our PW2 installation, which was completed on 6/21/18, and after 4 days of use my wife and I are totally blown away with our two-PW2 system performance. We are operating our PW2's in self-powered performance mode. Our utility meter has not moved in three days indicating no draw of electricity from the grid, and yesterday we generated 76 kWh off of solar and exported 75 percent of our generated electricity back to grid, after charging up the PW2 batteries, running the house and charging our two Tesla's. So now we have ceased to be consumers and are generators of electricity. In my view solar + PW2 is a no brainer and game changer indeed, and I think Tesla-Energy will sell a lot of these systems going forward.

steveturner | 25 giugno 2018

A few quick questions please:

- Are your combined generator/PW2 systems setup to run your entire house load in the event of a grid failure?


- When the grid fails does the combined system work like a "whole-house UPS", automatically switching over to power the house from the inverters and PW2s while grid is down?

Yes, this has happened twice.

- If so, how long does the switch-over really take? I've read posts from early users saying it can be instantaneous, so fast that a PC would not reboot after the switch. Has that been your experience?

It happened so fast that I was not aware the the grid was down.

- Any chance of getting a look at your systems sometime?

I am in Dade City, Fl. I have a 10.5 kwh system with 2 Powerwalls.

Thanks in advance. I can be reached: patrick at aeropartners dot com or eight one three, three nine zero, seven one zero nine.

Patrick | 25 giugno 2018

@TeslaDavid - good for you! Thanks for sharing the info. Sounds like our PV generators have roughly the same performance but it sounds like your home loads are substantially lower than ours. This time of year we generate 70-80 kWh per day but our consumption is in the same range and sometimes more.... With no PW2s we just build-up a kWh credit with Duke Energy winter/spring and then draw it back down in the summer and fall, resulting in an average net-zero situation each year.

Just curious - which energy company do you use? Any idea if or how much they will pay you for all your extra generation and when?

Patrick | 25 giugno 2018

@steveturner - perfect! I was hoping to hear this. Thanks for sharing. Please email me offline and maybe we can connect sometime soon.

Tesla-David | 25 giugno 2018

@Patrick, we have a very generous incentive program here in Washington State which pays us $0.54/kWh if we have solar panels and inverters made in WA state, which I do. I have Itek Panels made in Bellingham, WA, and Bluefrog microinverters also made in Bellingham, WA. Our electricity provider cuts us a check for $5k/year, and that is the maximum upper limit, which we have qualified for the past five years, and expect to get this year as well. Snohomish Public Utility District is our electricity supplier, and our electricity here is predominately hydro based, which gives us a low rate of $0.10/kWh.

We have also done extensive energy reduction retrofits to our 1987 home which have dramatically reduced our energy demand. We also swapped out our gas furnace and gas water heater for electric heat pump and heat pump water heater, so we are 100 percent electric. Our electric use during the summer is very small (generally less than 9 kWh/day), and as an example only averaged 2.6 kWh/day last month as a reference point, and our solar production averaged 60 kWh/day for May 2018. Last year we were 182 percent (solar production/energy demand), which covered our home and EV charging requirements, while exporting all the excess solar back to grid. I have attached link to that certification, which provides a summary of what we have done here. With the PW2 installation we exported yesterday 75 percent of our solar yesterday back to grid, so we are way good this time of year. We do not produce enough solar during November, December, and January to cover our energy loads, but do the remaining 9 months of the year. We have been Net Positive for past six years and our home was certified as a Net Zero Energy Building (NZEB) by the International Living Future Institute in 2016.

Patrick | 26 giugno 2018

Good for you - love that $5K! Thanks for sharing the info.