Stuck with 100amp Service from PG&E. HELP!!

[who177e]

Also, while a main breaker is a convenient way to kill all the circuits in the panel, when doing electrical work in the panel it is safer to kill the upstream breaker feeding the panel, so that there are no energized parts within the panel.

Cheers, Wayne

Thanks @wwhitney for all of your knowledge and expertise! This is super helpful to know that this configuration works and is safe, but I just need to convince PG&E of this and get their sign off.

On a side note, when I add the powerwalls, in order to get the 30% tax credit, it states that the powerwall needs to be 100% charged by the PV system (to get all of the 30% tax credit). With the diagram that I have shared, would this fit the bill? Currently, the solar inverter feeds the subpanel and the powerwall would feed the same subpanel. The inverter isn't directly connected to the powerwall so how would the powerwall know to only take power from the inverter and not the utility grid?

 

[miimura]

Thanks @wwhitney for all of your knowledge and expertise! This is super helpful to know that this configuration works and is safe, but I just need to convince PG&E of this and get their sign off.

On a side note, when I add the powerwalls, in order to get the 30% tax credit, it states that the powerwall needs to be 100% charged by the PV system (to get all of the 30% tax credit). With the diagram that I have shared, would this fit the bill? Currently, the solar inverter feeds the subpanel and the powerwall would feed the same subpanel. The inverter isn't directly connected to the powerwall so how would the powerwall know to only take power from the inverter and not the utility grid?

If you don't want to change the service and don't touch anything in the Combo Meter Panel, then I would not bother with PG&E any more and just apply for the permits with your city/county/AHJ.

Regarding the tax credit, the details of how stuff is connected doesn't really matter. What matters is the charging strategy of the battery system. In the USA, Tesla has enforced the charging strategy for any system configured with solar. It will only charge with solar energy, as measured by the system. It measures the grid power flow and solar production with current transformers and a Neurio energy meter. The Powerwall energy flow is directly reported to the Gateway by digital communication.

 

[wwhitney]

If you don't want to change the service and don't touch anything in the Combo Meter Panel, then I would not bother with PG&E any more and just apply for the permits with your city/county/AHJ.

Adding PV or Powerwalls requires an Interconnection agreement with PG&E, so they will certainly be involved. They will review the proposed size of the system to see if any upgrades to their equipment will be required.

Even if just adding an EV, it is best to notify PG&E (and certainly required if you want to switch to the EV-A rate plan). PG&E will also check in this case if their equipment may require upgrading.

Cheers, Wayne

 

[miimura]

Adding PV or Powerwalls requires an Interconnection agreement with PG&E, so they will certainly be involved. They will review the proposed size of the system to see if any upgrades to their equipment will be required.

Even if just adding an EV, it is best to notify PG&E (and certainly required if you want to switch to the EV-A rate plan). PG&E will also check in this case if their equipment may require upgrading.

Cheers, Wayne

Yes, sorry, I worded it poorly. A solar installer will clearly know what PG&E will allow and will apply for the interconnection on your behalf. They will also do all the load calcs to satisfy the building permit. It sounded like the OP was working with PG&E on the service upgrade, so if he's given up on that, then there's no need to talk to the PG&E service engineer any more. The solar interconnection will automatically trigger PG&E to look at the transformer serving your house to see if it is sufficient and any upgrade would be at their cost, not the homeowner's. Of course, notifying your local PG&E office of a new EV charging load is also strongly recommended.

 

[Kendall]

I have a similar question, I'm trying to understand why PGE does not have to pay for the trenching and panel upgrade based on this article. This seems to me like it should be common service which means its spread out of all rate players.

Project Cost Range

""Please Note: According to an interim policy, if a service upgrade is required, the facility upgrade costs associated with electric vehicle chargers at residential sites are treated as a common facility. As a result, the individual customer is not responsible for these costs. Normally, customers are responsible for costs that exceed the $1,918 allowance that PG&E provides. For more information, see the CPUC decision.""

 

[Shygar]

So PG&E pays for $1918 then you pay the rest? I would assume it can get pretty expensive. Plus with the whole bankruptcy, I am guessing things like this might get even harder to approve.

 

[Kendall]

Well I'm not sure they have any choice this is required by the CPUC which governs them bankruptcy or not. As I read it if a panel upgrade is required for a EV PGE must pay the full cost.

 

[Shygar]

PG&E is in San Ramon so you can just go knock on their door and ask them

 

[hs315]

Hello @who177e, I stumbled upon this thread while researching solar installation on 100amp panel with no space. I'm currently in the same situation as you described in your original posting a year ago. Can you please share your inputs on what configuration/setup you ended-up with for your home?

Thanks!

 

[who177e]

Hello @who177e, I stumbled upon this thread while researching solar installation on 100amp panel with no space. I'm currently in the same situation as you described in your original posting a year ago. Can you please share your inputs on what configuration/setup you ended-up with for your home?

Thanks!

Hi @hs315

Here was by existing setup. 100amp main panel with only space for a 2 pole 100 amp breaker that fed a subpanel that had all of the home loads.

After A LOT of back and forth to Teslas design team / and electrical team (a whole other conversation about how frustrating that was) and my city's building department, here is what I ended up with. I put in a 150amp rated subpanel between my existing 100amp main panel and the sub panel with all of the home loads. In the NEW subpanel I fed in the Solar PV and I also added an EV charger after the PV was installed and signed off on.

 

[hs315]

Hello @who177e, thanks a ton for your prompt response. The project manager I am working with suggested a somewhat similar setup but it helps to know that you have this working.

My house sq footage is 2100 and the recommendation I got from 2 vendors was 3.3 to 3.7KW based on our last year PG&E usage trend. I don’t have an EV right now but similar to you I have a phase2 plan to purchase one and I want the system to scale to the future need. How many KW does your installation produce? how many panels does it correspond to? For us, One vendor is proposing 11 panel LG and the other 12 panel Silfab. I have not looked into Tesla panels. Do you recommend them?

Thanks!

 

[miimura]

Hello @who177e, thanks a ton for your prompt response. The project manager I am working with suggested a somewhat similar setup but it helps to know that you have this working.

My house sq footage is 2100 and the recommendation I got from 2 vendors was 3.3 to 3.7KW based on our last year PG&E usage trend. I don’t have an EV right now but similar to you I have a phase2 plan to purchase one and I want the system to scale to the future need. How many KW does your installation produce? how many panels does it correspond to? For us, One vendor is proposing 11 panel LG and the other 12 panel Silfab. I have not looked into Tesla panels. Do you recommend them?

Thanks!

Don't count on anything scaling. If you plan to get an EV, just get the right amount of solar to start with. It's a huge hassle to add to it later. I am going through that now - wanting more solar because of EV usage.

 

[who177e]

Hello @who177e, thanks a ton for your prompt response. The project manager I am working with suggested a somewhat similar setup but it helps to know that you have this working.

My house sq footage is 2100 and the recommendation I got from 2 vendors was 3.3 to 3.7KW based on our last year PG&E usage trend. I don’t have an EV right now but similar to you I have a phase2 plan to purchase one and I want the system to scale to the future need. How many KW does your installation produce? how many panels does it correspond to? For us, One vendor is proposing 11 panel LG and the other 12 panel Silfab. I have not looked into Tesla panels. Do you recommend them?

Thanks!

We have a 1,855 sq ft single story house. The initial recommendations from multiple companies based on our usage was about the same as what you got as well but this was before we get a model 3. We ended up upsizing the system to account for the EV. I drive about 70 miles a day (mostly highway miles) and we use about 30 - 40 KwH a day now with charging the car everyday.
We have a 5.76kw system (18 x 320 watt panasonic tesla panels). In the peak of summer the most I've gotten was 42 kWh in a day. I haven't gotten to my full year true up yet with PG&E but it looks like because I'm charging the EV overnight during the super low rates $0.11 per kWh and we are getting credits during peak, I'm hoping that in the end we aren't paying anything. Currently my true up estimate is $71 of the year.

We went with Tesla because of 3 main reasons.
1 - the sleek edges (I know probably not the best reason since its just cosmetics)
2 - They were the cheapest we found out of the 4 companies we got quotes from. We paid $3.38 per watt with Tesla. We got prices between $3.38 - $4.04 from 8 different companies around the SF Bay Area. I heard that recently Tesla lowered their prices and are not below $3 a watt.
3 - the integration with the Tesla model App (again probably not the best reason)

Full disclosure thought, Tesla was horrible to work with. I knew that this would be the case going into it but we still chose them anyway. I had to basically be the project manager for the whole project. My "sales guy" was useless at getting my questions answered. I had to call the their design team, electrical team, directly to get answers and work through the system design. Even then the people working their didn't talk to each other and were not knowledge about the requirements or who internally could make a determination if a specific electrical design works or not. I had to interface with my building department to get the design approved and I had to work directly work with PG&E to get my system signed off one because the Tesla people were very slow and they often made mistakes on paperwork. During the install the crew was nice but it was clear that they just wanted to get the job done quickly. I had to oversee the job and told them exactly how I wanted the conduit run (based on aesthetics), I had to point out to the guy on the roof that he needed to level all of the panels because it didn't seem like he was going to do it on his own. It was a huge pain but in the end I am happy with the system.
I'm not sure if Tesla internal processes have gotten any better but this was the experience I had in November of 2018.

My recommendation - If you want the spend the least and if you don't mind micromanaging the whole process and like getting involved every step of the way, then I think Tesla would be a good choice.
If you want a turn key solution with good customer service, don't go with Tesla.

 

[hs315]

Thanks @miimura for your advice.

And thanks @who177e for all the details. It does sound like an unpleasant experience but I am glad it ended well.

I think I can make an informed decision now

 

[Jedddelucia]

Hi,

I am in a similar situation just up the road in Walnut Creek. I would like to have a system with panels, an EV level 2 charger (preferably the Tesla charger but I’ll settle for my existing 30a dryer outlet) and a powerwall.

My contractor is telling me that PG&E will refuse to install any size system with both elements on my existing service because the battery alone is more than my 100a service can handle (requires a 30a breaker and PG$E limits a 100a service to a 20a breaker for backflow.) I could switch to the LG batter but still could not have an EV charger. They tell me PG$E will not allow an upsized subpanel/bus with a derated main as in your diagram.

How did you get this through?

FWIW- My original system was 25 Panasonic 330w panels with the powerwall. This was oversized for my needs but the max I could fit on the roof. It was estimated to produce about 11-12K kWh/yr. I currently use about 7-8K/yr and added a model 3 on top which I fully charge twice a week so I estimated about 3K kWh/yr for that.

Add the new EV TOU pricing and I wanted some head room. EV-A is going away soon to be replaced by EV-2a. Which will look like this: peak 4-9pm= $.46/kWh, part peak 3-4p and 9-12p = $.35/kWh and the faceslap: off peak 12a-3p =$.15/kWh...

Good news for EV drivers who work from home and are without solar, but seems specifically targeted to harm solar producers... 3:1 cost ratio between production hours and evening use. Thus my interest in the battery.

So currently choosing between paying for the trenching and getting the full system, or downsizing panels and finding a way to have a smaller system while keeping the battery and a 50a breaker for the Tesla charger.

So @who177e: do you mind sharing any permit #s, correspondence with PGE for approving this system, or system drawings? It my help me prove my case to the AHJs to show prior approval.

Also, I take it that you did NOT do the trenching, but did PG$E give you any indication of what they would pay for? We’re they prepared to do the conduit and feeder?

Does anyone have a link to the CPUC regarding PG$E providing these service upgrades? A link to the language of the decision or something other than the vague description on PG$E’s website would be handy.

Thanks!

 

[who177e]

Hi @Jedddelucia

We have a 30amp PV backfeeding into our 100 AMP service and this was approved by our building department. The 30 AMP PV backfeeds into the 125AMP rated subpanel. So based on the 120% rule you can in theory backfeed 50 amps into the 125 amp rated subpanel but Tesla was telling me that Union City does not allow this. I emailed my city building official directly to discuss options and to see if he would approve this. He wanted to see my home load calculations to make sure our we would be under the allowed. Tesla included a future 30 amp EV charger into the calculations (I ended up installing a 60 amp for the Tesla charger knowing that the M3 won't use that much juice and I will only be charging the car overnight). After the building official reviewed he just said to make sure the load calcs were in the plans when submitting for the building permit. I did not include a PW into the plans because I don't think it would work with a 100 amp service and I don't think that the cost of the PWs can be justified.
I don't think that PG&E would have an issue with this as long as there is an approved building permit. The PG&E paperwork that was submitted for PTO, lists that we have a 100 amp service with PV system size and it was approved.

I did NOT do any trenching as the trenching alone would have cost $20k!
I did go back and forth with PG&E on what they would pay for. After a lot of emails and phone calls, PG&E will ONLY cover the cost of running the actual wires. Trenching and laying of the conduit is on the homeowner apparently. I've spoken with the CPUC as well.

 

[wwhitney]

We have a 30amp PV backfeeding into our 100 AMP service and this was approved by our building department. The 30 AMP PV backfeeds into the 125AMP rated subpanel. So based on the 120% rule you can in theory backfeed 50 amps into the 125 amp rated subpanel.

To clarify, the 120% rule applies to every panel between the meter and the PV connection. So if your PV connection is at a subpanel, you also need to consider the main panel. If that main panel has a 125A bus and a 100A main breaker, great; but if it has a 100A bus and a 100A main breaker, it becomes the limiting constraint, and you can only backfeed 20A of PV under the 120% rule.

Cheers, Wayne

 

[who177e]

To clarify, the 120% rule applies to every panel between the meter and the PV connection. So if your PV connection is at a subpanel, you also need to consider the main panel. If that main panel has a 125A bus and a 100A main breaker, great; but if it has a 100A bus and a 100A main breaker, it becomes the limiting constraint, and you can only backfeed 20A of PV under the 120% rule.

Cheers, Wayne

Hi @wwhitney

Why would that be the case?

I have a main 100 amp panel with a 100 amp breaker that feeds into a 125 amp rated subpanel. In that subpanel is my PV backfeed 30 amp breaker and a 100 amp breaker that feeds another sub panel with home loads.

I thought that the 120% only applies to the panel that the PV backfeed is in since the main panel bus is protected by the 100 amp breaker.

 

[wwhitney]

Any panel that can be fed by two separate connections needs to have its bus checked for possible overloading. The 120% rule is the most commonly used allowance, but there are others.

Consider the following case: a main panel, with various branch circuits and a breaker for a feeder to a subpanel. In the subpanel are various branch circuits and the PV interconnection. Obviously the subpanel is being fed from two different connections, so if you want to use the 120% rule for the subpanel, you need to have the PV interconnection on the opposite end of the bus from the feeder connection, and check the 120% allowance.

However, in the case that none of the subpanel loads are active, but all of the main panel loads are active, the main panel is also being fed via two different connections: the utility connection and the PV connection, via the feeder between the two panels. So if you want to use the 120% rule to protect the main panel bus, you have to ensure your breaker for the feeder is at the opposite end of the bus from the utility connection, and you check the 120% allowance.

Cheers, Wayne

 

[who177e]

Any panel that can be fed by two separate connections needs to have its bus checked for possible overloading. The 120% rule is the most commonly used allowance, but there are others.

Consider the following case: a main panel, with various branch circuits and a breaker for a feeder to a subpanel. In the subpanel are various branch circuits and the PV interconnection. Obviously the subpanel is being fed from two different connections, so if you want to use the 120% rule for the subpanel, you need to have the PV interconnection on the opposite end of the bus from the feeder connection, and check the 120% allowance.

However, in the case that none of the subpanel loads are active, but all of the main panel loads are active, the main panel is also being fed via two different connections: the utility connection and the PV connection, via the feeder between the two panels. So if you want to use the 120% rule to protect the main panel bus, you have to ensure your breaker for the feeder is at the opposite end of the bus from the utility connection, and you check the 120% allowance.

Cheers, Wayne

Hi @wwhitney

My main panel only has space for a single double pole breaker that feeds the subpanel that has the PV backfeed on it so there are no other loads that would be active on the main panel.