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New Powerwall install - gateways and app questions

New Powerwall install - gateways and app questions

Hi everyone,

I just completed my powerwall survey and wanted to ask if any on the forum could comment on certain issues that came up.

I have 400 A service coming to my electrical meter, but as is usual around here for residential clients, they split the lines after the meter in 2, 200A lines which go to 2 200A main panels. I also came to understand that the powerwall gateway only supports 200A capacity, so it seemed like this was a good thing the way my home was wired. I want to do a whole home backup of the service, and was told that it is possible to do this, but:

1)I will have to use 2 gateways for my plan of 6 powerwalls
2)I also was advised that each gateway can only carry a maximum of 3 powerwall units? Although I though the max capacity was 10 units, they mentioned that for every 3, you will need an additional gateway.
3)(and possibly most annoying of the concerns): I was advised that the app software can only show one gateway at a time, and that I would need to create another Tesla account in order to see the other gateway, with its own separate sign in and email address, but there is no way to see both gateways together, since it would be like "having 2 homes" with powerwalls installed and the app can only show 1 per sign in. They also mentioned this would have to be specially set up by Tesla IT since it is actually the same home address for the 2 powerwall systems/gateways.

Is this something that is planned to be changed in the future? A lot of residental customers have 2 200A lines coming from 400A service (because single 400A panels are huge and many times designed more for industrial applications I guess), so I would think it would be great if the Tesla app can support seeing both gateways in the same location/sign in. Also, they mentioned a work around would be to convert the service to a single 400A panel but I thought that the gateway can't support 400A anyway, and would need to have 2 200A gateways no matter what?

Please share your experience with installs already done or plans in process to confirm what I am saying, and any advice about how to set up this system?

Thanks!
Regards,
Peter Zambito

Patrick | 28 février 2020

Hi Peter,

We recently went through a very similar planning process for our new system with a 400A meter base and two 200A main breaker panels. We installed a 10 kW generator with 3 PWs back in December 2019. I posted some of our learning points here:

https://www.reddit.com/r/Powerwall/comments/ensh4r/powerwall_microgrid_w...

The system was fully commissioned in early January and we're nearing the end of our first full month of operations in Feb. So far everything is performing as advertised.

Regarding your questions - here's what I learned while doing research and monitoring early operations:

Item 1 - While many potential customers have 400A utility service at the meter base, so far the Tesla energy gateway (TEG) only supports a max load capacity of 200A at 240VAC. According to a few Tesla-certified dealers on the east coast, Tesla recently tested twin-TEG configurations with dual 200A breaker panels with good results. and as a result this is now their recommended setup.

There are some downsides to this approach for sure, including the issue you mentioned in Item 3, but it should achieve the desired results.

Item 2 - this may be inaccurate information. Unless something has changed, I don't believe two gateways are required to support more than 3 PWs. In fact, when we installed 3 PWs we left room in the generation breaker panel to add another PW in the future. Each PW can deliver up to 30A, and the PWs are connected in parallel to the load-side buss bar in the TEG via the generation panel, so a limit of 3 PWs per TEG does not make sense.

If you go with a twin-TEG scenario you will also need twin generation panels. The PW connections will then be distributed across the two generation panels. This should be done based on a) the actual loads connected to each main breaker panel in the home, and/or the desired amount of backup time desired for loads in each panel during grid outages.

Item 3 - again this is apparently the current best recommendation from Tesla. Not perfect, but it should still achieve the desired outcome of self-powering the entire home.

Unless Tesla has something new in the works it doesn't appear that this limitation will change in the near future. Thus we chose the alternative approach described in the Reddit post, which also works fine, but we will loose power to the secondary 200A panel during grid outages. With this in mind we just connected most of the important home loads to the primary 200A breaker panel powered via the TEG. We have a new construction scenario with lots of wiring flex, which allows for moving loads around to further optimize our backup capability during grid failures using a single TEG.

msparhawk | 29 février 2020

Thanks Patrick! I think I will be looking into doing 2 TEGs. Others on the forum have posted that they are able to see both gateways on the app , do you know is it really necessary to make 2 accounts or is there a way that Tesla can combine the two systems in one app sign in, just like how if you have more than one car on the same account it is just a matter of swiping left or right to see all the items in your account?

Peter

Patrick | 29 février 2020

Don’t know...

Please report back with observations after your system is installed. Would love to better understand how things work with two gateways.

bp | 29 février 2020

We went through the 1 or 2 TEG decision when planning our 15.4 KW solar/4 PW system with 2 150A breaker panels powering our house (a separate 150A panel for EV charging would stay on the grid).

Based on smart meter data for the last 2 years, we were able to verify we were below 200 A peak usage - and went with a single TEG for everything (except EV charging).

And with our system, we've been off-grid since Tuesday morning (except for EV charging) - 4 days and counting...

msparhawk | 29 février 2020

Thanks Patrick I will let you know what options come up with the 2 gateways when I actually complete the install.

@bp - exciting news! I look forward to seeing how much % off grid I will be able to do once solar+ powerwall is installed. I'm installing in new construction and in a community with an HOA, so for a few reasons solar roof will have to wait a bit so going ahead with powerwall first so at least I have backup for short power outages (most of them around here are not usually longer than 6-8 hours when they do happen)

msparhawk | 29 février 2020

Thanks Patrick I will let you know what options come up with the 2 gateways when I actually complete the install.

@bp - exciting news! I look forward to seeing how much % off grid I will be able to do once solar+ powerwall is installed. I'm installing in new construction and in a community with an HOA, so for a few reasons solar roof will have to wait a bit so going ahead with powerwall first so at least I have backup for short power outages (most of them around here are not usually longer than 6-8 hours when they do happen)

bp | 1 mars 2020

Splitting solar panels & PowerWalls between two Gateways running separate panels increases the complexity of the system while reducing the flexibility of adjusting power usage to extend runtime while operating off grid.

One decision we made early on was to keep our 2 HPWCs on grid power, because they can generate more load than the rest of the house. Instead, we had our installers add a 14-50 outlet to one of the panels connected to the TEG, so that we'd have the option of charging one vehicle of solar/PowerWall power - either during an extended outage (hurricane) or during consecutive full sun days when we had extra power to charge a car.

The contract with our installers provided for the option to split the system into two, should their projections on power usage be incorrect - which would have increased the labor and parts costs for the installation. Though they probably included that in the contract, because they were pretty confident the actual load on our two 150A panels was well below 200A.

Based on testing after our system was installed, while operating off-grid, it is possible for us to generate a load greater than 20 KW (the continuous power limit of 4 PowerWalls), if we turn everything on inside the house (two ovens, 3 pool pumps, 3 air conditioners, ...). But that's an unrealistic load - especially during a power outage, we wouldn't even try running both ovens... Under a more realistic load (everything except the ovens), we're below 20 KW.

NOTE we did have to get "hard start" upgrades (@ $300 each) for each of our air conditioners, because the burst power needed to start the air conditioners were beyond what the PowerWalls could provide.

Patrick | 1 mars 2020

bp - just curious - which brand and size/capacity are your AC units?

bp | 2 mars 2020

They're Lennox units - 2, 4 and 5 tons - installed in 2014.