3 inverters, 6 powerwalls, what to do

[tconvert]

I've been trying to get Tesla to help me solve this planning before I get an electrician to upgrade my service from existing 200amp. Maybe someone here has some thoughts if you're kind enough to suggest.
I have 2 Solar Inverters already (Solar City 2018, Tesla 2021) with 24 panels each.
I have 4 powerwalls presently. Large house with pool, now have 2 Tesla cars, 2 refridgerators, 2 AC's, large washer dryer, double oven, steam oven, etc etc etc. I plan to switch the two gas heaters to electric heat pumps. Only sharing so people understand why I want to upgrade electric service. I also just don't trust PGE is going to handle wildfires and massive incoming electric car demand as it grows quickly year/year. I expect outages to grow noticeably. I am in the East Bay of the San Francisco Bay area.

I have another order in for 2 more powerwalls and 1 more 24 panel Solar install ( 1 more inverter). They actually came to install then stopped that day when I mentioned I wanted to upgrade service (after waiting the standard 4-5 months for them to even start). They wanted me to do that first, so they left that day to have some free time. They don't respond to questions and my electrcian is stuck waiting for a plan/approach for his part. Guess they are pretty busy I expect.

I have done all the calculations. I won't even break even over 1year in my electric use with added Solar/powerwalls (about ~26kw Solar). I will still be using some PGE electric, mostly due to cars and commutes. The heatpumps I will swap in later will push the need higher for more PGE power.

My question is how to organize the wiring if I upgrade service to 300amp (or even 400amp but that takes a new outside panel). My understanding is the Tesla Gateway can't handle more than 200amp.
1. My outside panel and Meter are already rated for 300amp/320amp respectively. The outside panel has an unused area to add the extra 100amp circuit, while the main 200amp circuit is what is used today of course.
2. Tesla left a very large 400amp panel (max 325amp per "stab) in my garage that day. That apparently could take both the 200amp circuiit and the new 100amp if I added it. I don't understand how that would work unless they planned to connect the Tesla Gateway to the 200amp circuit only, and then the second was meant to not be backed up?
3. Can a Tesla Gateway even support 3 breakers for 3 Solar inverters and the 6 powerwalls. Apparently they can just connect a smaller load center and that should be ok to be able to connect it all. The Tesla Gateway has only 4 slots internally and all 4 are presentlyfull in mine so I guess they move them all out to another load center connected to it. I don't think that is too much for the Gateway.

I am assuming so far I will have to select a number of home circuits to put on the 100amp circuit which the Gateway will not backup (eg pool and maybe 1 car charger, steam oven,...).

Other thoughts? Or is there some way they were planning to have the Tesla Gateway with all the solar and Powerwalls connect to this large 400amp panel and do whole home backup. That doesn't seem right though load wise maybe. Thanks for any help/ideas.

I'll add the current wiring diagrams in the next post, too many for one post. I numbered them in the order electricity flows based on the wiring diagrams.

 

[tconvert]

Wiring I took a phone pict of.

 

[miimura]

You already have the larger service. You need to see how to use the amperage above 200A. I have a CL320 meter and a 200A main panel. There is an empty space for another main breaker above it. You need to decide which heat pumps you're going to buy and have Tesla design the system to accommodate it. In other words, find out what breakers the equipment will require so they can do all the load calculations as if they were installed. They may or may not have to use a second Gateway. They may also tell you that they can't install the system with the spare capacity and you will have to install the heat pumps before they install the additional Powerwalls and solar.

YOU DO NOT NEED ANY FURTHER SERVICE UPGRADE FROM PG&E.

 

[tconvert]

>>You already have the larger service. You need to see how to use the amperage above 200A
>>YOU DO NOT NEED ANY FURTHER SERVICE UPGRADE FROM PG&E

Thanks for the feedback! Agree, the panel is already 300amp, and the meter already is CL320. So no PGE work from the street to the house or to the meter.

Mostly just trying to see if Tesla can:
1. connect 3 Solar inverters and 6 powerwalls to one Tesla Gateway or is that too much. It would have to be via another load center it seems.
2. How does the Tesla Gateway flow to that large 400amp panel. I imagine the Gateway can only connect to one of the buses in the 400amp panel. Which means, if I had the electrican add another 100amp circuit (as you said to the empty space above in the current panel), that it would be on the other bus and not backed up by the Gateway. Or somehow can they connect the Gateway to that panel that it backs it all up.

I will probably just abandon the heatpump idea. The 300amp is just because I have so much load overall already, especially by adding the solar and powerwalls.

 

[h2ofun]

Why do you need more Powerwall? I have 5 and do not see they have saved me any money. Having the 30kw on solar is where I bank TONS of money with PGE, so much so that I get money back. I offer free EV charging to friends since getting back a few cents on the dollar is a waste. I basically put as many panels as my roof would fit, and get PGE approval for. I am SO far past the 100% rule, totally lucky. And I do have a 400 amp service, 2 200 amp subpanels, 99% electric with 3 heat pump compressors and 10 mini split heads. LOVE having the house at 70 during the summer and know I have a ZERO energy bill for the year!!

 

[BGbreeder]

>>You already have the larger service. You need to see how to use the amperage above 200A
>>YOU DO NOT NEED ANY FURTHER SERVICE UPGRADE FROM PG&E

Thanks for the feedback! Agree, the panel is already 300amp, and the meter already is CL320. So no PGE work from the street to the house or to the meter.

Mostly just trying to see if Tesla can:
1. connect 3 Solar inverters and 6 powerwalls to one Tesla Gateway or is that too much. It would have to be via another load center it seems.
2. How does the Tesla Gateway flow to that large 400amp panel. I imagine the Gateway can only connect to one of the buses in the 400amp panel. Which means, if I had the electrican add another 100amp circuit (as you said to the empty space above in the current panel), that it would be on the other bus and not backed up by the Gateway. Or somehow can they connect the Gateway to that panel that it backs it all up.

I will probably just abandon the heatpump idea. The 300amp is just because I have so much load overall already, especially by adding the solar and powerwalls.

One gateway can only switch 200A of load. If your remaining load can be shutdown during outages, one gateway will be sufficient. If you want all of your loads backed up, you will need two Gateways to switch the total load. Having two Gateways means that you would then have to partition the solar and the Powerwalls between the two Gateways to give the two parts more or less equal runtimes, and that guess will depend on whether the planned load is winter/summertime with large heat pump loads, or swing season. If it were me, I would be inclined toward something like heat pumps, cars, two solar arrays, and four Powerwalls on one Gateway, and one solar array, two Powerwalls, perhaps a backup car charger, and the house loads on the other. Part of the reason that I would put chargers on both systems is that if you guess wrong about the relative loads, or it is swing season, the EV charging gives you a way to level up the load amongst your three PV systems.

One item that I would keep top of mind is that a Powerwall has a max charge rate of 5kW, so you will need at least two Powerwalls per array to maximize your use of solar however you slice things up. I would consider a fifth Powerwall on the system with two arrays, just to reduce the peak charging current.

I think that you will need to add the heat pumps before adding your system; they are too many variables for an installer to guess at for them to do the job with any certainty without the actual heat pumps being installed. Plus, posts here have shown that finding an electrician willing to brave the "No further loads" stickers on the panels has proven difficult for others.

All the best,

BG

 

[tconvert]

Short answer. My last True Up payment was several thousands of dollars. But really, I just don't think PGE is going to handle well the wildfires and especially the quickly growing electric car demand for electricity. My cars eat way more electric than even my oven. I don't think the grid capacity is going to keep pace with that huge demand increase. They will upgrade it but my guess is each year that passes and more electric cars as % overall, their capacity is going to have problems they will be very slow to fix. While they increase their rates continually too. It's about 6-7 years for me to payoff all the money total, then it becomes a money machine. Faster payoff if they increase rates.

 

[BGbreeder]

I've been trying to get Tesla to help me solve this planning before I get an electrician to upgrade my service from existing 200amp. Maybe someone here has some thoughts if you're kind enough to suggest.
I have 2 Solar Inverters already (Solar City 2018, Tesla 2021) with 24 panels each.
I have 4 powerwalls presently. Large house with pool, now have 2 Tesla cars, 2 refridgerators, 2 AC's, large washer dryer, double oven, steam oven, etc etc etc. I plan to switch the two gas heaters to electric heat pumps. Only sharing so people understand why I want to upgrade electric service. I also just don't trust PGE is going to handle wildfires and massive incoming electric car demand as it grows quickly year/year. I expect outages to grow noticeably. I am in the East Bay of the San Francisco Bay area.

I have another order in for 2 more powerwalls and 1 more 24 panel Solar install ( 1 more inverter). They actually came to install then stopped that day when I mentioned I wanted to upgrade service (after waiting the standard 4-5 months for them to even start). They wanted me to do that first, so they left that day to have some free time. They don't respond to questions and my electrcian is stuck waiting for a plan/approach for his part. Guess they are pretty busy I expect.

I have done all the calculations. I won't even break even over 1year in my electric use with added Solar/powerwalls (about ~26kw Solar). I will still be using some PGE electric, mostly due to cars and commutes. The heatpumps I will swap in later will push the need higher for more PGE power.

My question is how to organize the wiring if I upgrade service to 300amp (or even 400amp but that takes a new outside panel). My understanding is the Tesla Gateway can't handle more than 200amp.
1. My outside panel and Meter are already rated for 300amp/320amp respectively. The outside panel has an unused area to add the extra 100amp circuit, while the main 200amp circuit is what is used today of course.
2. Tesla left a very large 400amp panel (max 325amp per "stab) in my garage that day. That apparently could take both the 200amp circuiit and the new 100amp if I added it. I don't understand how that would work unless they planned to connect the Tesla Gateway to the 200amp circuit only, and then the second was meant to not be backed up?
3. Can a Tesla Gateway even support 3 breakers for 3 Solar inverters and the 6 powerwalls. Apparently they can just connect a smaller load center and that should be ok to be able to connect it all. The Tesla Gateway has only 4 slots internally and all 4 are presentlyfull in mine so I guess they move them all out to another load center connected to it. I don't think that is too much for the Gateway.

I am assuming so far I will have to select a number of home circuits to put on the 100amp circuit which the Gateway will not backup (eg pool and maybe 1 car charger, steam oven,...).

Other thoughts? Or is there some way they were planning to have the Tesla Gateway with all the solar and Powerwalls connect to this large 400amp panel and do whole home backup. That doesn't seem right though load wise maybe. Thanks for any help/ideas.

I'll add the current wiring diagrams in the next post, too many for one post. I numbered them in the order electricity flows based on the wiring diagrams.

@miimura answered #1. You are good.
#2, if Tesla uses that main service panel, you will have a large load and a small load section. As you will have three arrays, that seems about right, and gives you the option of a second gateway (covered in my prior post) and fully backing up all your circuits.
#3 If you need more breaker space than are present in the Gateway, it is designed to have a subsidiary subpanel to take its 200A of allowed load.

If you do decide to go the partial backup route, with all of your solar and all of your Powerwalls on one Gateway, if I were you, I would consider adding another one or two Powerwalls just to reduce the peak charging current on the Powerwalls.

If you know that you aren't going to break even with the new system and that heat pumps will be additive to your load, is it possible to further upsize the third solar system while you are at it? (Budget, roof / ground mount space?)

All the best,

BG

 

[CrazyRabbit]

do a loads calculation for your house. download mike holts tool box, it will do loads calculation with everything you want backed up.

i have 320 amp service and two 200 amp panels. prior to battery install i replaced one panel with a 80 circuit panel and combined all my backup loads onto it. i left car chargers on non back up panel and one of the heater circuits. I'm all electric, resistive heat, three AC units, induction cook top, well pump, etc. while doing the panel upgrade, i added generator interlocks to the main panels and got a wgen12000df generator. i've used the generator twice so far, once for 4 hours and again for 1 hour.

i'm getting 8 powerwalls. i didn't want the system split like tesla wanted to do. i've got a 16Kw enphase system.

 

[tconvert]

According ot that tool @CrazyRabbit , I should be ok with 300A even if I did 2 heatpumps. Without the heatpumps it comes out larger than 200amp still. Thanks for the recommendation on that tool. I thought it would be too complex but was pretty simple to input circuits and get the output recommendation.

I think I will add the 100amp circuit to the existing panel and just move some non-backup loads to it of note like 1 car charger, oven, pool. Then let the Tesla gateway with 3 inverters, 6 powerwalls backup the rest on the 200amp circuit. At least see what Tesla says. Thank you both CrazyRabbit and @BGbreeder !

>>if I were you, I would consider adding another one or two Powerwalls just to reduce the peak charging current on the Powerwalls.
Is it possible the 3 solar inverters (just <26kw total solar) will push too much charge too fast to 6 pwoerwalls? Is that what you mean? Sadly My garage is crazy full; don't really have wall space now for more powerwalls without removing some wall racks for storage.

 

[BGbreeder]

According ot that tool @CrazyRabbit , I should be ok with 300A even if I did 2 heatpumps. Without the heatpumps it comes out larger than 200amp still. Thanks for the recommendation on that tool. I thought it would be too complex but was pretty simple to input circuits and get the output recommendation.

I think I will add the 100amp circuit to the existing panel and just move some non-backup loads to it of note like 1 car charger, oven, pool. Then let the Tesla gateway with 3 inverters, 6 powerwalls backup the rest on the 200amp circuit. At least see what Tesla says. Thank you both CrazyRabbit and @BGbreeder !

>>if I were you, I would consider adding another one or two Powerwalls just to reduce the peak charging current on the Powerwalls.
Is it possible the 3 solar inverters (just <26kw total solar) will push too much charge too fast to 6 pwoerwalls? Is that what you mean? Sadly My garage is crazy full; don't really have wall space now for more powerwalls without removing some wall racks for storage.

You are welcome!

There is a small chance that in an off grid situation if the house loads are low, and the solar is running that there will be too much current for the Powerwalls to charge. Given the size of your house loads, it is probably unlikely, but it has happened to other folks here. (If your max output is less than 30kW, it won't happen, so based on the above output, you are golden!)

All the best,

BG

 

[tconvert]

I wonder if they can combine last year's solar array 8.xkW 24 panel and this new 24 panel 9.xkW into one solar inverter. Then my Tesla Gateway doesn't change. Then they can just put the 2 new powerwalls into the 2 open spots in the existing powerwall load center. Seems SolarEdge has a large inverter maybe that could do this. I will ask.

 

[Powderkeg]

Mostly just trying to see if Tesla can:
1. connect 3 Solar inverters and 6 powerwalls to one Tesla Gateway or is that too much. It would have to be via another load center it seems.

Yes you can. I have the exact same thing installed running a 22KW system. The three inverters are Tesla 7.6KW

With respect to whether you need six powerwalls the answer is whether you can generate enough energy daily to fully charge them after you factor in your normal power usage. My gut tells me you do not and if that is the case you would be wasting your money.

 

[miimura]

Yes you can. I have the exact same thing installed running a 22KW system. The three inverters are Tesla 7.6KW

With respect to whether you need six powerwalls the answer is whether you can generate enough energy daily to fully charge them after you factor in your normal power usage. My gut tells me you do not and if that is the case you would be wasting your money.

I disagree. There is a balance between how much you want to cycle your Powerwalls versus how much you want to retain for backup power Reserve. Most of the year, I don't generate enough solar to fully charge my two Powerwalls. However, for 9 months of the year, I have enough solar to recharge the amount that I typically cycle the Powerwalls. IMHO, anywhere from 4 to 6 Powerwalls is appropriate for 17kW of solar.

 

[tconvert]

Thanks all. I am not worried. I am in deep east bay area past mt diablo. The new system is 9.x kw. I fill the 4 from the current 2 arrays before noon in the summer and by 2-3pm in the deepest of winter. Adding another array and 2 powerwalls is a good match to current ratio that is working really well.

 

[tconvert]

@BGbreeder @Powderkeg @miimura @CrazyRabbit
For histories sake and if it helps others later, Tesla came back and installed successfully. I didn't upgrade service to 300amp yet though the meter/panel is ready for it. I and an electrician did the caclulations just like Tesla did and the current 200amp is ok (but getting close). Thanks for the Mike holts tool, twas handy. So they did this on the existing 200amp circuit:
1. 3 inverters supporting 3 solar arrays totals <26kw. Two older ones, 1 new.
2. 6 powerwalls (4 originally)
3. 1 gateway backing up whole house. They attached a HUGE (almost as tall as my wife) load center to the Gateway--400amp panel, 325 amp per "stab". They put all the inverters and powerwall breakers in it. Way oversized, but I guess they needed that kind of load center rating.

The inverter for the new solar array was the new one I guess Tesla makes that sits on one of the powerwalls. The older 2 Tesla inverters for the older panel groups are Solar edge. Cool to see tesla making everything it seems now. Once they installed, I was getting almost 20kw flowing, bet it will reach around 21/2kw tomorrow around 11am.
Also new is a small button like shutoff that goes outside for the inverter/solar shutoff. The old way they did, including last year, was a large box with a shutoff handle. Now outside is this small button like switch. Much smaller and simple to meet the outdoor requirement of a shutoff.

TY for the help along the way.