Main Panel Upgrade After Solar Panel and Powerwall Installation

[jshutterbug]

I'm building a detached ADU (Accessory Dwelling Unit) in the back yard. Main house has a 100A main electrical panel with solar panels (not Tesla) that has Enphase microinverters.
I will be installing additional Tesla solar panels and 3 Powerwalls for the ADU.

Tesla designed the system based on existing 100A panel. They they can integrate new solar panels with the existing solars panels which will charge the Powerwalls which in turn can backup both the main house and ADU.

My question...if I upgrade my main panel after solar panel/Powerwall installation from 100A to 400A will I need to call Tesla to make any adjustments to the system? Any idea how much it would cost? Will it be difficult?

Tesla site technician came out for initial assessment and he recommended waiting until I upgrade to 400A panel first and then have Tesla do the install. Talked about having to do new calculations and that it'd be a headache to come back later and redo everything.

The problem is PG&E is taking forever to come back with a proposed design for my underground powerline upgrade. It's already been 4 months with no answer. ADU will be completed next month. Don't want to wait another 6 months+. I'm not sure if city will sign off on the ADU without the required solar panel system installed.

Thoughts?

 

[wwhitney]

Tesla is the low price leader, so they don't want to deal with complications. A competent designer could lay out everything both to work now, and to allow a service upgrade in the future with minimal or no rework.

Why 400A, instead of 200A? With 400A, full backup is not supported by Tesla; it's still possible with a clever third party design.

Cheers, Wayne

 

[h2ofun]

Tesla is the low price leader, so they don't want to deal with complications. A competent designer could lay out everything both to work now, and to allow a service upgrade in the future with minimal or no rework.

Why 400A, instead of 200A? With 400A, full backup is not supported by Tesla; it's still possible with a clever third party design.

Cheers, Wayne

400 amp is, I have it. I just use 2 gateways, and I am 100% backup my entire house. Nice and simple.

 

[wwhitney]

400 amp is, I have it. I just use 2 gateways, and I am 100% backup my entire house. Nice and simple.

Yes, I should have said with a single GW as a unified whole. Obviously you can divide your PV/loads/PWs up into separate 200A chunks.

Cheers, Wayne

 

[jshutterbug]

I decided to upgrade to 400A instead of 200A because I have to trench across the street to replace old powerlines. I don't ever want to do that again. The ADU will have a 100A subpanel and then the main house will get to use the rest eventually have electric car chargers installed.

So I just need to add another gateway to solve for the larger electrical panel? Or is it more complicated then that?

 

[wwhitney]

So I just need to add another gateway to solve for the larger electrical panel? Or is it more complicated then that?

Easiest is 100A backed up for the ADU, 100A backed up for the main house, and the 200A extra for non-backed up loads like EVSEs. Then you have one GW, one set of PWs, and one set of PV inverters.

If you have 6+ PWs, and lots of different PV inverters, you could divide those each in half, and have a completely bifurcated system with (2) GWs. As 400A services often just have (2) 200A breakers, that's a natural option.

Cheers, Wayne

 

[jshutterbug]

Easiest is 100A backed up for the ADU, 100A backed up for the main house, and the 200A extra for non-backed up loads like EVSEs. Then you have one GW, one set of PWs, and one set of PV inverters.

If you have 6+ PWs, and lots of different PV inverters, you could divide those each in half, and have a completely bifurcated system with (2) GWs. As 400A services often just have (2) 200A breakers, that's a natural option.

Cheers, Wayne

Thanks. My electrician also layed out 1.5" conduit for them to run any solar cables from the main house to the ADU. They told me they probably wouldn't be able to use it. I think they wanted a larger conduit. Not sure why but my existing solar panel wires fit in a 3/4" conduit. Will powerwall and solar lines fit in a 1.5" PVC conduit?

 

[jjrandorin]

Tesla site technician came out for initial assessment and he recommended waiting until I upgrade to 400A panel first and then have Tesla do the install. Talked about having to do new calculations and that it'd be a headache to come back later and redo everything.

You do not (repeat do not) want to be doing "anything" major to your home electrical, AFTER getting solar and powerwalls. No one will want to touch anything. Tesla isnt in the business of providing electrical modifications to your system after install, only supporting what they installed.

No one else will want to touch anything, with all the "do not touch" stickers all over it and the complexities of Solar and powerwalls. If you need to upgrade your main panel, go t 200, 400 etc service, ALLLL that should be done before you start on the PV / batteries.

If you go with tesla, getting those upgrades "later" is going to be virtually impossible. If you go with a higher touch contractor / pv company, they might support you for that stuff later, but it wont be cheaper doing it later with all the PV and batteries than it will now.

So, either "difficult and more expensive" than now, or "virtually impossible". Do all your upgrades first, and make PV / batteries last.

 

[holeydonut]

IMO, your situation seems like something to bring in @Vines , instead of trying to go with Tesla. By the time you add on all the extra whacky stuff that you're trying to accomplish, Tesla's low/introductory price will have jumped up anyway.

 

[h2ofun]

I decided to upgrade to 400A instead of 200A because I have to trench across the street to replace old powerlines. I don't ever want to do that again. The ADU will have a 100A subpanel and then the main house will get to use the rest eventually have electric car chargers installed.

So I just need to add another gateway to solve for the larger electrical panel? Or is it more complicated then that?

one gateway per 200 amp panel

 

[Vines]

I'm building a detached ADU (Accessory Dwelling Unit) in the back yard. Main house has a 100A main electrical panel with solar panels (not Tesla) that has Enphase microinverters.
I will be installing additional Tesla solar panels and 3 Powerwalls for the ADU.

Tesla designed the system based on existing 100A panel. They they can integrate new solar panels with the existing solars panels which will charge the Powerwalls which in turn can backup both the main house and ADU.

My question...if I upgrade my main panel after solar panel/Powerwall installation from 100A to 400A will I need to call Tesla to make any adjustments to the system? Any idea how much it would cost? Will it be difficult?

Tesla site technician came out for initial assessment and he recommended waiting until I upgrade to 400A panel first and then have Tesla do the install. Talked about having to do new calculations and that it'd be a headache to come back later and redo everything.

The problem is PG&E is taking forever to come back with a proposed design for my underground powerline upgrade. It's already been 4 months with no answer. ADU will be completed next month. Don't want to wait another 6 months+. I'm not sure if city will sign off on the ADU without the required solar panel system installed.

Thoughts?

My 400A service upgrade took almost a year and didn't require anything except a new aerial and an engineering review. They initially said 5-6 months but it ended up dragging on and on.

It sounds like you either wait for Tesla, and follow their instructions, or you explore alternate options.

1.5" Conduit ios useful but not nearly as useful as 2" conduit. If I didn't know better and had to finish things up I would add (1-2) 2" conduits for future use going from the ADU to the MSP area.

 

[jshutterbug]

Does anyone have any suggestions for contractors authorized to trench across the street to install electrical conduit and powerlines for underground powerline upgrade from 100A to 320A/400A?

Thanks!

 

[jshutterbug]

This would be for the SF Bay Area. I'm told the contractor would need a Class A Engineer license to trench across the street?

 

[Vines]

We work with FTG Builders often but am not sure they are small enough to take this work. They are a general contractor, and that is what you need here. We work often with Pete Moffat, RJ Dailey, and others.

Many construction companies are slammed with work right now and this work takes time.

 

[jshutterbug]

If my 400A panel will be split into two 200A breakers. One 200A line will be backed up by the Powerwalls (because a single Gateway can only handle 200A max), the other 200A line won't be backed up the by Powerwall (I'll use this line for EV charging in the future).

Will Tesla need to do any recalculations based on the above setup? Would going from 100A to 200A require any recalculations?
Sounds like going from 100A to 400A would require recalculations if I ended up using 2 Gateways (which I don't plan on doing).

At the end of the day, I'd like to know if Tesla can install my solar panels and Powerwalls (based on my existing 100A main panel). After Tesla is done with the installation, if I upgrade my underground powerlines to 400A split into two 200A breakers, will feeding the one 200A into the installed Gateway mess anything up?

Thanks!

 

[lensovet]

At a minimum, the wiring from the gateway to the load center would have to be redone for 200A service. It's not about calculations, it's about actual wires. Wires sufficiently thick for 200A will not fit into a 100A load center. As mentioned previously, Tesla is not going to come out and redo stuff after the installation is done unless something is broken.

Btw, you can have SunRun install Tesla gear. They will probably be more amenable to this.

I have no idea why you need 400A service.

 

[jshutterbug]

At a minimum, the wiring from the gateway to the load center would have to be redone for 200A service. It's not about calculations, it's about actual wires. Wires sufficiently thick for 200A will not fit into a 100A load center. As mentioned previously, Tesla is not going to come out and redo stuff after the installation is done unless something is broken.

Btw, you can have SunRun install Tesla gear. They will probably be more amenable to this.

I have no idea why you need 400A service.

Since I need to trench to replace my underground powerlines, I figured I might as well install 400A lines now rather then install 200A lines (and possibly have to upgrade again later. It would power both the main house (1,700 sq ft.) and ADU (900 sq ft).

By "load center" do you mean the main panel?
Can an electrician replace the wire between the Gateway and load center or does it have to be a solar installer? Does there need to be new software (or hardware) configurations?

 

[lensovet]

Yes what people call a “panel” is more appropriately called a load center.

I don’t know why you’d need to trench twice (or why you’d need 400A in the future). Can’t you install conduit to just pull the right wire later?

I can’t speak to what Tesla’s rules are in terms of other people touching their system later. But you’d need to replace the conduit too or ask them to oversize it when they design it.

 

[baysolarstream]

FWIW, I am in the same boat as the OP. PG&E pushed out the nearest transformer upgrade from December to late Q1 next year and so, I now have a timing issue. I have a 200A panel/service that I am upgrading to 400A. Telsa permits have been approved by the city but I don't have an installation timeframe from them yet. If they come back with earlier dates, I am leaning toward pushing out the solar installation to a date after the meter and main panel have been upgraded.

 

[jshutterbug]

PG&E said it would cost about $40k for them to do the trenching from across the street to my main panel!
Independent contractor would cost about $28k ($20k trenching + $8k PG&E fees) which is still a crazy amount to me.

I'm not sure if PG&E will need to upgrade the transformer that feeds my block. I'm assuming if they did, it'd take them a long time to do so.

Tesla said they can install the solar panels and Powerwalls from my 100A main panel. I know it's best to install solar after main panel upgrade to 400A (two 200A breakers) but that may take another year to happen. The ADU is 90% complete and the city won't sign off on final inspection until solar is installed.

If I have 100A panel, do you know if the electrical lines they install from the gateway to the solar panels and Powerwalls can handle 200A service? If I upgrade my panel later I wouldn't want to have to replace those electrical lines.

If I have 100A panel, I'm assuming they'll run a 100A electric line from the 100A main panel to the Tesla gateway. I'm hoping I'd only have to replace the electrical line from the main panel to the gateway when I upgrade to a 400A panel and not all the electrical lines after the gateway.

People must have upgraded their main panels after Tesla installed solar. How did these people handle the change? Did Tesla come back out or did they have to hire independent solar company or electrician to replace the electrical lines?