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Upgrading to 400 Amp service after Solar already installed

KPU73

New Member
Nov 29, 2021
3
0
San Fran
To start with I am NOT an electrician and have very little knowledge of electrical loads. We are in the process of a complete remodel of our home, and in order to "future proof" our house, our architect suggested upgrading our electrical panel as well. When I initiated the purchase of my solar system from Tesla in May, 2021, I also started a request to upgrade my existing service panel (main panel) to 400 amps from PG&E. Silly me thought that I would have had the new panel in way before Tesla would come to install the system. Tesla installed the solar system in September, 2021 and we got our PTO in February, 2022. PG&E finally gave us the approval for our panel upgrade in May, 2022. We have a 12.24 kW Solar system with 2 PowerWalls that is attached to our existing electrical panel. I can't get a straight answer from my GC, electrician or PG&E as to what our current service panel is? Some say it is 100 - others say it is 125 and others say it is 170. If that part wasn't frustrating enough, now we are in the process of trenching to install our new 400 amp panel and we noticed that the Tesla backup-switch on our meter says it is only rated for 200 Amps. Initially, we didn't know what this thing was, but we have come to find out that this is what provides our "whole house" to be backed up during a power outage. We recently had a power outage and this sucker worked flawlessly so we DO NOT want to be without it. PG&E doesn't seem to have any knowledgeable folks about what this thing does or how to integrate it with the new panel. I have been trying to contact Tesla for 3 months now to find out if I can use my existing "meter collar/backup switch" on a 400 amp service panel. I have called and emailed Tesla at their energy support email ([email protected]) for months and have not gotten ANY replies. I have asked if we could somehow “split” the 400 amp panel into two 200 amp panels, but PG&E will only allow us to have 1 meter – and if the Tesla backup switch/collar goes on that meter, I would no longer have the “whole house” backed up. I’m wondering if anyone else has come across this situation. We went with the 400 amp service panel because we wanted to have 2 Tesla chargers (we have 1 now). We also will have some upgraded appliances (Sub-Zero fridge; wine fridge). If anyone has a solution or suggestions on what we should do at this point or who I can contact, I’d really appreciate it. Some additional facts: We have underground service and we would have had to trench for 200 or 400.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
16,725
22,075
Riverside Co. CA
The tesla energy gateway (what you are calling the backup switch) is only rated for 200 amps. There is no way to back up 400 amps of service with one Tesla energy gateway.

AFAIK you have two choices:

1. Buy another Tesla energy gateway AND more powerwalls to connect to it (have two full systems that dont talk to each other)

Or

2. ensure that everything you want backed up currently (which should be everything you have backed up now, most likely) remains connected to the Tesla energy gateway and the panel its in now, and have the main service come in at 400amps, then split to (2) 200 amp panels, with one being backed up (and having everything you have in there backed up now) and anything else in the new non backed up panel.

Im not an electrician either, and most of what I have learned I learned from here. We have some very knowledgeable members in this subforum though, so if I am wrong, someone will likely correct me.
 
The tesla energy gateway (what you are calling the backup switch) is only rated for 200 amps. There is no way to back up 400 amps of service with one Tesla energy gateway.

AFAIK you have two choices:

1. Buy another Tesla energy gateway AND more powerwalls to connect to it (have two full systems that dont talk to each other)

Or

2. ensure that everything you want backed up currently (which should be everything you have backed up now, most likely) remains connected to the Tesla energy gateway and the panel its in now, and have the main service come in at 400amps, then split to (2) 200 amp panels, with one being backed up (and having everything you have in there backed up now) and anything else in the new non backed up panel.

Im not an electrician either, and most of what I have learned I learned from here. We have some very knowledgeable members in this subforum though, so if I am wrong, someone will likely correct me.
The problem is the OP has the Tesla backup switch and not the gateway, so he cannot do either of those options without purchasing a gateway for his existing system and having Tesla reconfigure the system to use the gateway which would probably mean also relocating all the loads to a new panel. Unless the OP has some serious loads other than what he mentioned I would stick with the 200A service or upgrade to 200A service if the current service is less and leave everything else as is.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
16,725
22,075
Riverside Co. CA
The problem is the OP has the Tesla backup switch and not the gateway, so he cannot do either of those options without purchasing a gateway for his existing system and having Tesla reconfigure the system to use the gateway which would probably mean also relocating all the loads to a new panel. Unless the OP has some serious loads other than what he mentioned I would stick with the 200A service or upgrade to 200A service if the current service is less and leave everything else as is.

I read "backup switch" and my brain inserted "backup gateway". I do realize there are two different things, but I didnt think there were a lot of installations with just the backup switch. You are likely correct though, in which case they are sort of stuck.
 
I have a 400 amp service entrance panel that has 2 200 amp breakers in it. One 200 amp breaker is feeds a few breakers that are in that main service entrance panel that aren't backed up. The other 200 amp breaker is to the Tesla backup panel, Powerwalls. Gateway, solar generation systems, etc. There is a 200 amp breaker that feeds a separate 200 amp sub-panel for my house.

There is no 400 amp meter mounted backup switches that I'm aware of (Tesla made me sign paperwork to have a backup switch on my meter but it couldn't be done). My Gateway acts as my backup switch.
 

KPU73

New Member
Nov 29, 2021
3
0
San Fran
Since I have to make a decision to upgrade our panel - the cost to go to 200 Amp vs. 400 Amp was almost the same - $1,500 difference - so $9.6K vs $11K. With all of the things in this world moving to eclectic, it just seemed to make sense to do the 400 amp now as I NEVER want to deal with this again. I would be fine to do a 400 amp panel - that splits into two 200 amp panels and put everything that we have now into the main 200 amp panel and perhaps just the 2nd charger into the other 200 amp panel and leave the rest sorta open for now and use it if I need to in the future. Would that make sense?
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
16,725
22,075
Riverside Co. CA
Since I have to make a decision to upgrade our panel - the cost to go to 200 Amp vs. 400 Amp was almost the same - $1,500 difference - so $9.6K vs $11K. With all of the things in this world moving to eclectic, it just seemed to make sense to do the 400 amp now as I NEVER want to deal with this again. I would be fine to do a 400 amp panel - that splits into two 200 amp panels and put everything that we have now into the main 200 amp panel and perhaps just the 2nd charger into the other 200 amp panel and leave the rest sorta open for now and use it if I need to in the future. Would that make sense?
Conceptually, it sounds like it makes sense, as long as you have a tesla gateway instead of the backup switch.
 
You need to purchase a Tesla gateway, sounds like you got the meter base switch (which will be junked). You will also need to find a Tesla authorized installer. You are just going to have to open your wallet $$$. who ever does the work will be taking over responsibility for the whole installation, so I’m thinking $4K profit on top of real work. You should have waited! I would move the existing house to a new 80 circuit 200 amp panel, try to get 225 amp bus bars. Connect that to your gateway, and add a generation panel and connect that to your gateway. Your new 400 amp service will power the gateway and any new big loads, such as pool, car chargers, and so forth and will not be backed up. Personally I would not back up a car charger, add a 50 amp outlet or two in the garage for things like a charger cord, welder…. Might as well add a generator interlock kit and receptacle to the new backup panel as well. Don’t do a combo meter base, do a dedicated meter base to a 400 amp service disconnect panel/switch then to your loads.
And since you are doing this work the whole house will have to be brought up to code $$$, TR recepicals, arc fault/ground fault circuits.
 
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like this... i combined two 200amp panels into the new 80 circuit 200 amp panel on the right. left panel only has two load circuits car charger and heater circuit in it. this is how i prepared for my 8x Powerwall setup with small solar installation from tesla. i have an existing 56x panel enphase system...

F2054295-F521-463C-88D8-0A40B1994FDB.jpeg
 
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To start with I am NOT an electrician and have very little knowledge of electrical loads. We are in the process of a complete remodel of our home, and in order to "future proof" our house, our architect suggested upgrading our electrical panel as well. When I initiated the purchase of my solar system from Tesla in May, 2021, I also started a request to upgrade my existing service panel (main panel) to 400 amps from PG&E. Silly me thought that I would have had the new panel in way before Tesla would come to install the system. Tesla installed the solar system in September, 2021 and we got our PTO in February, 2022. PG&E finally gave us the approval for our panel upgrade in May, 2022. We have a 12.24 kW Solar system with 2 PowerWalls that is attached to our existing electrical panel. I can't get a straight answer from my GC, electrician or PG&E as to what our current service panel is? Some say it is 100 - others say it is 125 and others say it is 170. If that part wasn't frustrating enough, now we are in the process of trenching to install our new 400 amp panel and we noticed that the Tesla backup-switch on our meter says it is only rated for 200 Amps. Initially, we didn't know what this thing was, but we have come to find out that this is what provides our "whole house" to be backed up during a power outage. We recently had a power outage and this sucker worked flawlessly so we DO NOT want to be without it. PG&E doesn't seem to have any knowledgeable folks about what this thing does or how to integrate it with the new panel. I have been trying to contact Tesla for 3 months now to find out if I can use my existing "meter collar/backup switch" on a 400 amp service panel. I have called and emailed Tesla at their energy support email ([email protected]) for months and have not gotten ANY replies. I have asked if we could somehow “split” the 400 amp panel into two 200 amp panels, but PG&E will only allow us to have 1 meter – and if the Tesla backup switch/collar goes on that meter, I would no longer have the “whole house” backed up. I’m wondering if anyone else has come across this situation. We went with the 400 amp service panel because we wanted to have 2 Tesla chargers (we have 1 now). We also will have some upgraded appliances (Sub-Zero fridge; wine fridge). If anyone has a solution or suggestions on what we should do at this point or who I can contact, I’d really appreciate it. Some additional facts: We have underground service and we would have had to trench for 200 or 400.
The best way to use the backup switch in your situation is to install a separate 200A meter socket, fed from the top 200A main breaker of your 2x200 service panel. Install the existing backup switch in that meter socket

The bottom 200A breaker and the distribution bus would not be backed up in this case, but at least you don't need a whole new system design.

Of course, a Tesla Gateway would also be a great solution, and the cost may not be much more than the solution I just outlined.
 
If you have a 400 amp electrical service, installing Tesla power walls becomes complicated because as others have said their gateway is rated at 200 amps which will be satisfactory for the vast majority of homes. Therefore my answer to the OP's question is:

If you are not having any problems now, I would leave things alone. Don't fix what ain't broke.

I have ordered my Tesla solar system without the battery system as I would need about 9 powerwalls for my house. It would pretty much require ripping out all the main electrical equipment where the meter and main disconnects are installed. Since I have a 60 KW generator, which has no problem running the whole house during power outages, I have just decided to leave that in place and install only the solar system.

Consider the following:

I have a large house with a 600 amp service and 3 200 amp panels and use a lot of power, living in SE FL. The house is all electric except the cooktop and hot water is gas. It has 5 A/C units and 2 one-ton mini-split units for the 2 two-car garages. The house also has 45,000 watts of electric heat which if all on at the same time (which does not happen) would draw 187.5 amps. We run heat here for just a few hours a year when the temperature dips down into the low 50's or high 40's a few days a year.

IMG_1016.JPG


This next photo shows the 600 amp meter installation. There are two parallel runs of 4/0 AL cable coming in to the top of the meter from the POCO, and each panel is fed by a run of 3/0 copper coming off the bottom of the meter through three 200 amp main disconnect/transfer switches. I took the photo when the POCO changed out the meter to a "smart meter". The POCO sizes their wire based on expected voltage drop on the real-world load, not the NEC ampacity tables. I have seen houses with 200 amp services fed with #2 AL triplex overhead cable.

IMG_0640.JPG


The following screen shot is very typical of our electrical usage during a hot July day. The usage at 3 - 6 AM shows a peak for the day because my Tesla MXP is charging. I have it set to charge so it is finished by 6 AM. Unless I have driven the car below 50% it usually starts charging during the 3 or 4 AM hour. Clearly the Tesla causes us to hit our peak usage during the early hours of the morning.

Screen Shot 2022-07-30 at 11.42.54 AM.png


You only need the capacity for your peak load. It does not matter how many stoves, ovens, air conditioners, water heaters, pool pumps, or other things you have.

Assuming the usage in the 5 AM hour is continuous, nearly 21 kWh of usage during that hour is equal to about 88 amps (21,000 ÷ 240 = 87.5). I know what is on at that time, 2 air conditioners for the bedrooms and the Tesla (at 48 amps) are the large consumers of electricity during this time, along of course other smaller items may be on such as refrigerator, freezer and other things that consume very small amounts of electricity. Therefore this is a rough calculation. It also assumes a power factor of 1. If the power factor is .9 then the amps would be almost 100 amps.

Clearly, at all other times our average electrical demand is less than this. This graph shows average use for each hour. However, the instantaneous peak load throughout the day will peak considerably more than the hourly average, but if the average hourly load is increased 50% to allow for peaks the peak load is under 150 amps. If the peak was 100% more then the peak load would be around 200 amps.

The points I am trying to make are that unless you have real world data you cannot know what you need and that most people (and the NEC load calculation methodology) overestimate the amount of power they need. You should try and get this information if you can get it from your POCO. If not, do a load calculation for your house. Only once you have the facts should you decide to spend the money to upgrade and then only if the facts require it.

If you will be charging an EV there are additional ways to mitigate the need to upgrade your service, such as installing this device (DCC-12)


We have a Tesla Model Y on order for my wife. Obviously we have plenty of juice available to charge two EVs at the same time, but if I didn't I would use the power sharing capability of the Gen 3 wall connector or if not a Gen 3 I would program the individual Tesla wall connectors to limit the charging to an amount so as to not overload the capabilities of my electrical service. And if not using Tesla Gen 3 (or another brand of wall connector), installing the above referenced DCC-12.

I hope the above comments have helped you, and good luck!

(I am not an electrician, but I am a retired electrical engineer.)
 
I have a large house with a 600 amp service and 3 200 amp panels and use a lot of power, living in SE FL. The house is all electric except the cooktop and hot water is gas. It has 5 A/C units and 2 one-ton mini-split units for the 2 two-car garages. The house also has 45,000 watts of electric heat which if all on at the same time (which does not happen) would draw 187.5 amps...
Wow... looks like your house could use an energy audit! (Or it is over 12,000 square feet.)
 
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I just sent Tesla this message:
“I just spoke to Fort Worth building department. They said as long as I comply with table 302.6 it is allowed. I do not have living space above the garage. And the adjoining wall complies with noted table.
The outside location to install Powerwall's is on the north side of the house adjacent to bedrooms, bedrooms are on north side of house; so I that is not acceptable to me. By the time fire alarms go off the attic will be fully engulfed and could possibly collapse on to me before the alarms go off.
I can install, and planed on installing a heat detector fire alarm in the garage connected to my monitored burglar alarm/fire alarm system..”
EA1B7CD0-EABF-413A-9DC5-0F891E715CA6.jpeg



My garage is fully dry walled…. With no living space above garage. I see NO issues.
 
Wow... looks like your house could use an energy audit! (Or it is over 12,000 square feet.)
8,500 s.f. + 2 two-car garages each with 1 ton mini splits. Garages have insulated overhead garage doors.

The house could easily have been set up with a 320 (so-called 400) amp service. But I am glad it has 480 (so called 600) amp service since it could support an EV in each garage bay!

The load calculation that is required these days is IMO unrealistic. Just one example...it assumes 3 watts per s.f. for "general lighting". This is over 25 kW for an 8500 s.f. house. With all LED lighting, the actual load is more like 500 watts with ALL lights on.

Before I had my EV I turned on everything in my house, all lights, all air conditioners, both ovens, both dryers, both washing machines, all TVs, all computers, pool pump, almost everything, and the load was about 135 amps, measured with a clamp on amp meter. At 240 volts, that is about 32 kW, or to be more precise, 32 kVA. Maybe both refrigerators and the freezer were not running at the time, so it could be a bit more than 135 amps, but not that much more. Certainly not 320 amps!

With all the electric heat on it would be substantially more. With the oven in self clean, it would be a bit more. But still not over 320 amps. Most people over estimate how much capacity they need.

All the above said, setting up charging for an EV, or multiple EVs requires some careful study especially if being installed on a 200 amp (or less) service.

As an example, I have a friend who has a large house, about 4500 s.f., that only has a 200 amp service. The house has gas heat, gas hot water and gas cook top, and he has a Model S and a Model Y and charges after midnight with no problems. If they are both charging at the same time, the load would be almost 100 amps. This is not a problem because there are no other large loads like electric heat. So this works in his case, but if he had 20 kW of electric heat it would not work, or he would have to configure the EV charging equipment to manage the load to keep it below whatever was necessary so as to not overload his service.

I would like to hear from the OP what he ended up doing. Sounds from his July 20 posting that he determined he actually did not have a 200 amp service and needed to upgrade to at least 200 amps. I'd like to have a list of the 240 volt circuits in his house to try and see if it is really necessary to upgrade to 400 amps. 200 amp service is so much easier to deal with for whole house backup using a single Tesla gateway for everything. But it might make sense to have a sense to have a panel not connected through the gateway for the EV charging and any other high amp circuits that do not need to be backed up or are not desirable to back up regardless if he goes with 200 or 400 amp service.

Another thing to consider: Even if a house has a 200 amp main breaker, it does not mean the house is capable of supporting 160 amps continuous load, which would be about 38 kW. The POCO will only install the capacity for what the expected load is. This could be the transformer serving your house and the wires feeding your house.

At one time I lived in a ~3,000 s.f.house where I installed two heat pumps that had supplemental and back-uo electric heat. The POCO determined it was necessary to upgrade both the transformer and the wires feeding my house from 2 AWG to 4/0 AWG, but the existing 200 amp panel was fine.

So in the OP's situation that might mean he needs to install new wires, but not a new panel or both the wires and the panel need to be upgraded. And It is not always possible to determine the amp rating of a panel, there are many ways to configure an electric service. Is there a meter main, with a few high amp circuits off the meter main before the main panel, a split buss panel, etc? A few photos showing all panels would also help.

Hope the above is helpful!
 
Besides the DCC, another company also makes an EV load shedding device:


Less expensive than the DCC. Can be purchased at Amazon.

Installing such a device on whatever panel you now have negates the requirement to do any upgrades to transformers, wires, panel size just to install an EV. Of course, there might be other reasons to upgrade your service.
 
Since I have to make a decision to upgrade our panel - the cost to go to 200 Amp vs. 400 Amp was almost the same - $1,500 difference - so $9.6K vs $11K. With all of the things in this world moving to eclectic, it just seemed to make sense to do the 400 amp now as I NEVER want to deal with this again. I would be fine to do a 400 amp panel - that splits into two 200 amp panels and put everything that we have now into the main 200 amp panel and perhaps just the 2nd charger into the other 200 amp panel and leave the rest sorta open for now and use it if I need to in the future. Would that make sense?
Pretty much every 400A panel I have ever seen is split into two 200A subpanels (mine is setup this way). I've never seen a residential 400A main panel with a single 400A busbar and main breaker. You will have one main breaker per subpanel, and the meter/service line will be capable of 400A. What I did was I have 200A for the house one one subpanel, and 200A for the cars on another subpanel. If I ever get a generator transfer switch, it goes on the house subpanel (the cars don't need to be backed up).
 
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h2ofun

Active Member
Aug 11, 2020
4,004
1,012
auburn, ca
Pretty much every 400A panel I have ever seen is split into two 200A subpanels (mine is setup this way). I've never seen a residential 400A main panel with a single 400A busbar and main breaker. You will have one main breaker per subpanel, and the meter/service line will be capable of 400A. What I did was I have 200A for the house one one subpanel, and 200A for the cars on another subpanel. If I ever get a generator transfer switch, it goes on the house subpanel (the cars don't need to be backed up).
I have 400 amp service, 2 200 amp subpanels. I have 2 gateways. I have 2 ATS switches for the 22kw generator.
 

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