Can Powerwall contribute to homes amperage?

[STS-134]

Your numbers are fine, but they don't account for escalating and unpredictable time of use rates that PG&E and other utilities will impose on consumers in the future. your numbers are a good starting point but in reality the math improves due to increasing rates. off peak rates alone have doubled in the past several years.

Rate increases do not improve the math, and increases in off peak rates actually hurt the math. What matters is not the absolute price of off peak or peak rates but the difference between them. The Powerwall is, in effect, an electrical usage time shifting device.

Besides oversizing the system which is also costly, battery storage is the only way to counter time of use rates. my system (panels + pw) is expected to pay for itself in 6-7 years since I replaced all my gas appliances and it's offsetting $2.5k-$3k annual electricity bill and gas bill is poof. Had I didn't get a pw, I would have needed to install more panels to offset peak rates.

Right, but I'm not discussing the solar portion, only the Powerwall portion. If you didn't have the Powerwall, you couldn't store the solar energy, and would have to sell it to PG&E at off-peak daytime rates. Then you'd need to actually draw from the grid during peak rates instead of using your storage. We've already determined that, if the PW lasts exactly its warranty period and breaks 1 day after, you'd be paying 29¢/kWh for the privilege of storing that energy. It follows that you'd better be getting more than 29¢/kWh in value out of storing it and using it later instead of selling it immediately and drawing from the grid later on. Given that:
1. The PW can store 13.5 kWh of usable energy
2. There are 2557 days in 7 years
3. The total amount of energy you'd be able to store and consume during peak hours in 7 years, assuming you charge it fully every day and exhaust it completely every day, is 2557*13.5kWh=34519.5 kWh
4. There are 121 annual days in the PG&E "summer" season (June 1-September 30) where you get 31.251¢/kWh stored
5. 7 years' worth of "summer" days is 7*121*13.5 = 11434.5 kWh @ 31.251¢/kWh
6. The rest of the energy, 34519.5-11434.5 = 23085 kWh, is used during the non summer season, and you benefit from it to the extent of 18.54¢/kWh

So let's add everything up:
(11434.5 kWh * $0.31251/kWh) + (23085 kWh * $0.1854/kWh) = $7853.354

I don't see how that PW possibly pays for itself in 7 years. And this is if you're charging it to 100%, AND if you make sure to use the entire capacity of the PW, such that it hits 0 usable kWh stored at 8:59:59 pm every night. If there ANYTHING left in the PW the moment 9 pm rolls around, then make the payback time even longer. And you'd better not ever go on vacation and stop using as much peak electricity from your PW either.

And note that there is another option here: get solar without storage, and as you'd be using more energy during peak times, switch to ETOU-C or ETOU-D. I'm probably paying about a 10¢/kWh premium over EV2-A during offpeak, but I am saving about 8¢/kWh during peak times (summer), 11¢/kWh during partial-peak times (summer), 5¢/kWh during peak times (non summer), and 7¢/kWh during partial-peak times (non summer). Combined, my cars consume about 400 kWh/month, so I'm paying about $40 more to charge them per month than I would on EV2-A. But then I need to subtract off the savings for cooking dinner, running the AC, etc.

I checked my usage on two months: last month and mid-summer. Peak usage last month was around 80 kWh. During mid-summer, it was around 140 kWh. That means 2-5 kWh/day. So anyway, the most I'd save with a PW, assuming I wanted to go on EV2-A, would be (140 kWh/summer month)*(4 summer months)*($0.31251/kWh) + (80 kWh/non summer month)*(8 non summer months)*($0.1854/kWh) = $293.66 per year. On an $11000 investment, that's a 2.67% annual rate of return. Quite frankly...that's awful. I can get WAY better than that investing money in other things. And even worse, when you typically make an investment, you get a return on that investment, and you get all of your principal back at the end. But a Powerwall is a piece of technology and a consumable item, and it depreciates to $0. And unless you're purchasing it for a business, you can't even write off the depreciation; you get nothing back when it's done and "used up", so it not only has to give you a higher return than you'd get elsewhere, but the savings it gives you must return all of your principal back over its lifetime too. Given a savings of about $300 a year, when is that going to happen? It would take more than 35 years just to return my principal back in (highly depreciated) dollars. I suppose this could happen in much less time if you are a very heavy peak electricity user but as I've already shown above, it literally cannot happen within 7 years.

to me it was worth it since I wanted to "complete" the system with panels and power wall plus, we haven't even talked about power outages and for that, the value placed on it is dependent on the individual and can't be assigned a value with math.

That is indeed the only thing that I think the Powerwall provides that's somewhat useful: automatic emergency backup 240V split phase power. Automatic emergency generators and transfer switches are pretty costly, about as much as a Powerwall. But my power goes out 0-3 times per year, for maybe a few hours each time. It's annoying, but it doesn't annoy me to the extent that I'm willing to throw $11000 at it. And the "no build" option (where you invest the money in something else instead) should always be considered. I get some of the benefits of a Powerwall with a portable generator and extension cords, minus the ability to cook on my cooktop or run the AC. If the power goes out on an extremely hot day, I could always go elsewhere or even put the car in camp mode.

 

[tfan2018]

You can’t buy a powerwall by itself without solar panels so the payback should be based on both solar panels + powerwall. I don’t know why you insist on isolating the ROI calculations on powerwall alone. I don’t know what to say besides the fact that after 6.5 years my solar panels + powerwall will pay for itself, I don’t really need to calculate the ROI on the powerwall alone, I just care about the payback of the system as a whole. If I didn’t opt for a powerwall, I would have had to spend thousands more for more panels to offset peak usage. By buying a powerwall, I didn’t need as many panels (even though it would have been nicer to have more). At the end of the day some things that people buy aren’t entirely driven by it’s ROI. I like seeing the solar panels and powerwall in my app, it makes me happy and at the end of the day that’s what matters most anyways . If the math doesn’t work for you and buying it makes you unhappy then don’t buy it, but it’s different for everyone

 

[STS-134]

You can’t buy a powerwall by itself without solar panels so the payback should be based on both solar panels + powerwall. I don’t know why you insist on isolating the ROI calculations on powerwall alone.

No it shouldn't, because you can:
1. Not get solar panels at all
2. Buy solar panels without a Powerwall

We're looking at what a Powerwall adds to the solar setup. Here's an example: I can invest in a stock, let's call it stock A, that goes up to 1000% of its original value in a year, and that gives me a 10x ROI in a year. I can also invest the same amount of money in stock B, which loses 100% of its value in the same year. Overall, my total "stock market return" is 900%, or 9x, given that I made 10x on stock A but lost all of the money I put into stock B. Pretty good, right? I suppose you'd tell me that I should look at the ROI calculation of all of my stock market investments together? Well, that's only true if I were forced to buy stock B in order to buy stock A. But since I had the option to buy either stock A alone, or stock B alone, or not buy any stock at all, we should look at everything separately. And it turns out that stock B was a terrible investment, despite me getting a 900% return overall. What I should have done was put more money into stock A instead. The only scenario where it makes any sense to put money into stock B is if I were forced to do it in order to buy stock A, because the return on stock A is so high, it more than cancels out the losses on B. But if I don't have to buy B at all, I shouldn't.

In the case of solar/PWs, there are 4 possible scenarios:
1. Invest in other stuff
2. Buy solar only
3. Buy solar and PWs
4. Buy PWs only (which we disregard, because this isn't an option)

So anyway, in order to find out whether the PW is a good investment, we compare (2) and (3). To find out if solar is a good investment, we compare (1) and (2). (3) may give you a positive return on investment compared to (1), just like buying both stock A and B did in the example above, but if the rate of return on the extra money you had to pay for (3) compared with (2) is lower than (2) compared with (1) or even negative, then you probably would have done better doing more of (2) and none of (3).

I don’t know what to say besides the fact that after 6.5 years my solar panels + powerwall will pay for itself, I don’t really need to calculate the ROI on the powerwall alone, I just care about the payback of the system as a whole. If I didn’t opt for a powerwall, I would have had to spend thousands more for more panels to offset peak usage. By buying a powerwall, I didn’t need as many panels (even though it would have been nicer to have more).

What would your payback time have been if you had:
1. Bought only the same amount of solar and invested the Powerwall money in something else?
2. Bought more solar panels in lieu of a Powerwall?

 

[tfan2018]

If I didn’t buy the powerwall I wouldn’t be as happy as I am now so there’s that What is the payback period for more happiness.

 

[dareed1]

@STS-134 Many of us have commented that it is difficult to make PWs "pencil out", but I have to say that your calculations above are burdening the PWs with too much cost. We added solar and PWs in November 2020. The installed cost for two PWs was $16,000 and we received a 26% Federal tax credit. So the cost to us was $12,160 for two, or 55% of the cost you've been using.

This doesn't change the basic reality that the PWs are not a good "investment" (assuming NEM2 allowing me to bank energy to run our heat pumps in the winter), but I chose to buy them anyway. I'm not willing to run a generator during power interruptions, and I like the seamless transition from grid to back up power. I get a non-rational enjoyment out of not pulling any power from the grid during June to September. In other words, I don't consider PWs to be an investment at all, and so evaluating the purchase on that basis doesn't make sense to me.

 

[h2ofun]

unfortunately I have a limited budget so my system is smaller than I would have wanted, but it should be enough for 1 EV plus all home usage for now . we don't have AC but we may add it in the future...

great setup you got there!!

This is why I comment, if one has a choice of a battery or more panels, put on the panels, IMO

 

[STS-134]

@STS-134 Many of us have commented that it is difficult to make PWs "pencil out", but I have to say that your calculations above are burdening the PWs with too much cost. We added solar and PWs in November 2020. The installed cost for two PWs was $16,000 and we received a 26% Federal tax credit. So the cost to us was $12,160 for two, or 55% of the cost you've been using.

Yeah, apparently they used to be $3000 for around 6 kWh of storage. Then about $6000 for 13.5 kWh. At those prices, it's a lot easier for it to pay for itself. Now, the pricing has just gotten ridiculous.

This doesn't change the basic reality that the PWs are not a good "investment" (assuming NEM2 allowing me to bank energy to run our heat pumps in the winter), but I chose to buy them anyway. I'm not willing to run a generator during power interruptions, and I like the seamless transition from grid to back up power. I get a non-rational enjoyment out of not pulling any power from the grid during June to September. In other words, I don't consider PWs to be an investment at all, and so evaluating the purchase on that basis doesn't make sense to me.

Yeah, I get that. But what this entire thread was about was using Powerwalls as an alternative to a service upgrade. This doesn't make any sense, especially when you're building an ADU and already have all of the contractors on site for other stuff. OP should do a service upgrade to 400A first, then get solar and storage later on when prices for that stuff fall.

 

[wwhitney]

Agree that for the OP a service upgrade is in order, and PWs are not a viable alternative. Worth considering whether it would be easier/cheaper to have the new service on a stand-alone pedestal (if PG&E allows that) or on the new ADU, and then resupply the main house from it.

I checked my usage on two months: last month and mid-summer. Peak usage last month was around 80 kWh. During mid-summer, it was around 140 kWh. That means 2-5 kWh/day.

You used only 80 kWh in a month, how'd you manage that? My recent year Energy Star 23 cubic foot refrigerator says it uses 700 kWh/year, or 60 kWh/month. So I think you must have an error in your data.

Here's an example: I can invest in a stock, let's call it stock A, that goes up to 1000% of its original value in a year, and that gives me a 10x ROI in a year. I can also invest the same amount of money in stock B, which loses 100% of its value in the same year. Overall, my total "stock market return" is 900%

It would be a 500% multiplier, or a 400% gain. I.e. start with $100, put $50 in each stock, end with $500.

Cheers, Wayne

 

[STS-134]

Agree that for the OP a service upgrade is in order, and PWs are not a viable alternative. Worth considering whether it would be easier/cheaper to have the new service on a stand-alone pedestal (if PG&E allows that) or on the new ADU, and then resupply the main house from it.

So what I did was put the new panel in a slightly different location, and the location of the previously outside facing main panel became a new inside facing 200A subpanel. Just had to put stucco over the old spot where the main panel was and then paint it. Connect the main panel to the new subpanel using wiring that's capable of handling 200A and that handles all of the house circuits (this way, the electricians did not have to pull all of the many wires supplying the house circuits over to another spot, and could simply label them, mount the new subpanel in the same spot, and connect everything). My other 200A subpanel is just for the cars; in the OP's case, it could be for the ADU. Or 100A for the ADU and 100A for the cars.

You used only 80 kWh in a month, how'd you manage that? My recent year Energy Star 23 cubic foot refrigerator says it uses 700 kWh/year, or 60 kWh/month. So I think you must have an error in your data.

80 kWh during peak hours, i.e. Monday-Friday 5-8 pm. The vast majority of my usage is during off-peak hours. I obviously almost never charge the cars, run pool pumps, etc., during peak hours because I have an economic incentive not to do so.

It would be a 500% multiplier, or a 400% gain. I.e. start with $100, put $50 in each stock, end with $500.

Cheers, Wayne

Yep. And I can't edit that post anymore.

 

[TerranApart]

To the OP: when you called the PG&E service planner, even if they required a larger underground conduit for 200A service, did they have any options larger than 100A (such as 125A) that might be available with your existing underground conduit?

Here in SCE service territory, there's a similar requirement (3" conduit needed for 200A), but it seems like they are allowing those on 100A service with 2" conduit to go to 125A, in at least some circumstances that I've seen.

Of course, every company has different standards, but it might be worth asking, since it could mean a modest improvement over 100A for the cost of a new main electric panel rather than 20-30k for trenching a new 200A service.

That said, I agree with others here for the best long-term solution being 200A, especially powering two dwelling units.

 

[jjrandorin]

Re-running the numbers with EV2-A (31.251¢ price delta between peak and off-peak): need to run $11000/$0.31251= 35199 kWh through the unit for break-even. Except that only applies during June-September. During the rest of the year, the price delta is just 18.54¢/kWh, and you'd have to run 59331 kWh through it. Realistically, it's probably about 2/3 of the way between the two, or around 50,000 kWh. But remember, the warranty is only good for 37800 kWh. Let's take the high end of your estimate, 7 years, which is about 2557 days (if there's two leap years in there, not that it really matters for this analysis though). 50000 kWh/2557 days=19.55 kWh/day. Wait a minute...the PW only holds 13.5 kWh of usable energy (plus if you use 100% of its capacity daily, it'll degrade rapidly and won't even be able to supply 13.5 kWh). So I'm not sure how you get a payback period of 6-7 years.

This analysis assumes, of course, that you have 19.55 kWh/day of load that you absolutely cannot shift to other times and must use the Powerwall to provide. If you are capable of shifting your usage, the payback time gets even longer.

The warranty is not for 37800, thats the warranty if charged from the grid. Charged from solar its "unlimited KWh"

 

[jgleigh]

A couple of points.

Powerwall pricing isn't linear.

$11K for 1
$18K for 2
$25K for 3
$32K for 4

And that is before federal tax credits. And what is the likelihood that the Powerwall gives up 1 day after the warranty expires? Even if the battery has degraded below 70% capacity it is still quite useful. And the battery cycles are unlimited for solar applications as @jjrandorin said.

Not to mention, in places without 1-to-1 Net Metering we end up selling back to the utility at a fraction of what we buy it at.

 

[jjrandorin]

This is all a different discussion than the OP's question though. I think most of us would say that the OP needs a service upgrade, and expecting somehow the powerwalls to make up for that is not realistic.

The rest of the discussion is a rehash of "are powerwalls worth it", and I am personally not into that discussion.

 

[STS-134]

To the OP: when you called the PG&E service planner, even if they required a larger underground conduit for 200A service, did they have any options larger than 100A (such as 125A) that might be available with your existing underground conduit?

One issue with a lot of older buildings (1980s and before) is that there is probably not a conduit at all. PG&E used to do "direct buried" lines, where the wiring was placed directly in the ground without any conduit. Trenching is required to install a conduit and anything that's not a "like for like replacement" (same capacity as the old panel) needs to meet current PG&E greenbook requirements. Currently, I believe that the conduit size required for 200A and 400A is the same, but there's no guarantee that PG&E won't update the greenbook again to require something else. That's why I went all the way to 400A; once you have the 400A main panel installed, you're grandfathered at 400A even if they change the requirements in the future (if you go to 200A instead and at some point it is no longer enough, and the greenbook has changed, you'll have to pay someone to dig another trench).

 

[jshutterbug]

Thanks for the lively discussions and detailed calculations.

Below are the cost breakdown for the solar panels and Powerwalls (before Federal tax credit).
4.8kw panels = $12,048
3 Powerwalls = $25,000 (as another poster mention 1st Powerwall is $11k, 2nd one is $7k, 3rd one $7k)
Total = $37,048 ($27,202 after 26% Federal Tax Credit).
I'm required to buy solar panels since the ADU requires its own solar panels even though the main house already has 4kw panels. I figured I'd buy the Powerwalls now before the Federal Tax Credit disappears (who knows).

Tesla said they can set up the system so both solar panel systems can recharge the Powerwalls. Also, when PG&E shuts of power for days due to wildfires here in CA or high winds as a preventive measure, the Powerwalls will be able to provide power to both homes (which is a plus). Otherwise I'd have to deal with Generac generator which I don't want to deal with hooking it up to gas.

My parents will be living there for a number of years b4 turning it into a rental so that'll give me a trial period of how this system will work out. If it doesn't, and I still need to trench to upgrade my panels, then I'll go that route. Home battery solutions will probably be less expensive in the future but there might not be any Federal Tax Credits available anymore and who know with inflation what pricing will be. From what I've read Tesla increased pricing on their cars $10k vs last year.

The numbers might not pencil out but ultimately comes down to what someone will pay for convenience. Even if I paid $25k-$30k to trench/replace powerlines, electricans were quoting me an additional $4k for upgrading electrical panel to 200A. I'm assuming upgrading to a 400A panel would be costlier. That was last years price. I'd still want to install Powerwall for backup at most a year later.

Prices in SF Bay Area (NorCal) are ridiculous.

@TerranApart Existing panel is 100A. PG&E said I'm not able to upgrade to even a 125A panel (I tried to do that when I replaced my old Zinsco box). Home was build in 1976 and powerlines were apparently direct buried. PG&E said a 3" conduit is required for any service over 125A.

The funny thing is (not really), when PG&E came out to my property, their map said the underground box was across the street but they couldn't find it. They came back a couple more times and was never able to find it. I wanted to know where the box was so I could get a general idea of how far across the street they would need to trench. I'm assuming it would be significant more expensive trenching 100' vs 200'. PG&E requires a $1,500 deposit to put together a plan and provide a cost estimate.

When the electrician runs the line from the main house to the ADU, I'll have to ask them size the lines in case I want to upgrade my panels later.

Yes, I agree 200A or 400A would be best long term solution but since I can't buy Powerwalls by themselves this was my only opportunity to get them with my solar panels. Battery backup from other manufacturers (Enphase) were alot more expensive after installation costs and there were no discounts for additional units.

How do people living off grid using Powerwalls make it work? Do they need crazy amount of panels and Powerwalls? Let's say for average 1,500 to 2,000 sq ft house.

 

[jshutterbug]

I think another reason I'm leaning towards Powerwalls is more psychological. If I didn't have underground powerlines, it would be a no brainer to upgrade the service panel. It would cost $5k at most to replace the powerlines? That means $15-$25k is just for digging a trench! It's all labor cost (probably paying for a bunch of guys standing around) whereas I'm getting something physical with a Powerwall.
Apparently, only certain contractors can trench across public streets as it requires a special license.
Maybe I'll have bite the bullet and spend $1,500 for PG&E to provide an estimate. Why couldn't it be more like $300.

 

[jshutterbug]

One issue with a lot of older buildings (1980s and before) is that there is probably not a conduit at all. PG&E used to do "direct buried" lines, where the wiring was placed directly in the ground without any conduit. Trenching is required to install a conduit and anything that's not a "like for like replacement" (same capacity as the old panel) needs to meet current PG&E greenbook requirements. Currently, I believe that the conduit size required for 200A and 400A is the same, but there's no guarantee that PG&E won't update the greenbook again to require something else. That's why I went all the way to 400A; once you have the 400A main panel installed, you're grandfathered at 400A even if they change the requirements in the future (if you go to 200A instead and at some point it is no longer enough, and the greenbook has changed, you'll have to pay someone to dig another trench).

Did you have underground powerlines? How much did it cost for you to replace your lines? Was upgrading to 400A alot more expensive vs. going with 200A? Would 400A require PG&E to upgrade the neighborhoods transformer? If so, I'm assuming that's something I would need to pay for (which benefits my neighbors).
Some in a different forum mentioned the $1,500 for PG&E is just a deposit for them to figure out how much it will cost to upgrade powerlines. It's for labor hours. If they end up figuring out the calculations quickly, they refund you the difference. If they spend a lot more time on the calculations, they bill you for it. I wonder what labor rate they use. What I hate are the unknowns. PG&E can tell me they spent X amount of hours calculating my needs. I wouldn't know if they're padding their hours.

 

[Vines]

Did you have underground powerlines? How much did it cost for you to replace your lines? Was upgrading to 400A alot more expensive vs. going with 200A? Would 400A require PG&E to upgrade the neighborhoods transformer? If so, I'm assuming that's something I would need to pay for (which benefits my neighbors).
Some in a different forum mentioned the $1,500 for PG&E is just a deposit for them to figure out how much it will cost to upgrade powerlines. It's for labor hours. If they end up figuring out the calculations quickly, they refund you the difference. If they spend a lot more time on the calculations, they bill you for it. I wonder what labor rate they use. What I hate are the unknowns. PG&E can tell me they spent X amount of hours calculating my needs. I wouldn't know if they're padding their hours.

If the transformer is shared, PGE will pay for the upgrade. When it is dedicated, the customer must upgrade it. The $1500 is credited toward the eventual work.

My evaluation was just under $100, and they refunded the rest. No upgrade was required. However, I had an overhead feed so much easier.

 

[STS-134]

Did you have underground powerlines?

Yes.

How much did it cost for you to replace your lines?

~$1950: PG&E engineering cost
~$6300: Trenching cost. Quoted $7000 for digging a trench to the PG&E box on the street. Got a 10% discount for paying cash. Used this company (although they CAN do trenchless construction, I used the open trench method). The other company I got a bid from was not competitive at all - they gave a quote for over $9000. The other option is to have PG&E itself do the trenching; this usually costs more than hiring an independent contractor.
~$8000: Electrician labor & supplies (new panels, breakers, install of Tesla WC, etc.)

Was upgrading to 400A alot more expensive vs. going with 200A?

Not a lot, considering the expenses associated engineering the project and having the trench dug just to put in the conduit. The trenching company's charges were not affected by whether I did 200A or 400A at all. The options were (labor + supplies included in both quotes):
- 400A combination service entrance device w/ integrated 200A subpanel for cars ($4000) + 200A subpanel for house circuits ($2500) OR
- 200A main panel and service entrance ($3500)

There were a few charges in the final bill that weren't in the original quote due to the price of copper surging, the fact that I wanted a whole house surge suppressor installed, etc. But overall, it was an extra ~$3000 to make sure that I never, ever have to pay $7000 for another trench. If the trenchers need to cross the street to get to the PG&E lines, this will probably increase trenching costs (and put the economics even more in favor of the 400A option).

My existing, outside-facing main panel and service entrance was changed to an inside facing 200A subpanel and the outside wall where the old main panel used to be was covered with new stucco; the panel itself is pretty much in the same location as the old one as therefore the electricians didn't have to move all of the wiring from one place to another (reduced labor costs). The new subpanel was connected to the combination service entrance device with wiring that can handle 200A.

Pretty much all 400A service entrances will not have a single 400A breaker, but will have 2x200A breakers right behind the meter (apparently because 200A breakers are much cheaper than single 400A breakers, and they don't really make 400A busbars for residential applications). There are also 400A service entrances without integrated subpanels, where you have two subpanels elsewhere. This may be better if you are, for example, converting your existing 100A panel to a 200A subpanel and adding a new subpanel for an ADU.

One option I considered, but didn't take, was to split the 400A into separate portions ahead of the meters (yes, two meters) so that I could have one rate plan for the house and another for the cars (PG&E EV-B tariff). The EV-B rates are better than the EV-A rates and would have allowed me to keep the house on a better plan for use of AC while still making vehicle charging as cheap as possible, but this would have segmented my service into two separate portions and I think in general, static partitioning is not good. If I were to have done 200A for the house and 200A for the cars, what happens if I later decide I want 250A for the house? Remember, PG&E can change the rates and there's no guarantee that EV-B will be better than other rates in the future, or that it will even continue to exist (Southern California Edison has in fact phased out their dedicated EV meter plan - no new approvals for that plan and I have not heard what they plan to do with people still on the plan in the long run). But this IS an option and when you are doing a service upgrade is the time to

Would 400A require PG&E to upgrade the neighborhoods transformer? If so, I'm assuming that's something I would need to pay for (which benefits my neighbors).

I was not required to pay for this. Do you know how many houses are on the existing transformer? If yours is the only one, maybe you'd have to pay for it. If it's 2 or more, I doubt it. Underground transformers are typically either completely underground (you'll see a large (at least 3' by 6') covering in someone's yard that says "PG&E" on it) or they are large green above ground boxes that say high voltage/danger on them. If you drive around your neighborhood, you'll probably be able to see how many of these things there are, and estimate how many houses are on each one. And when you get the engineering drawing from PG&E, it'll let you know exactly which ones are on your transformer.

Some in a different forum mentioned the $1,500 for PG&E is just a deposit for them to figure out how much it will cost to upgrade powerlines. It's for labor hours. If they end up figuring out the calculations quickly, they refund you the difference. If they spend a lot more time on the calculations, they bill you for it. I wonder what labor rate they use. What I hate are the unknowns. PG&E can tell me they spent X amount of hours calculating my needs. I wouldn't know if they're padding their hours.

Yeah, I'm not exactly sure, but they charged me around $1950 for their portion -- inspections, running the new service lines, etc. There was around $450 in additional charges beyond the initial $1500 deposit. There was supposedly an allowance of around $1800 that comes from the PUC as well.

Since I had an independent contractor do the trenching, and I took the option of handling the permits with the city by myself (as opposed to having one of the contractors handle it, which would have cost more), I had to coordinate a whole bunch of activities. As you can probably tell, a project like this has a lot of "moving parts" and as the homeowner, it's your job to keep them moving. Overall, the process was like this:

- Contact electrician, ask for a quote on service upgrade. Get part number/brand of the service entrance device from electrician
- Contact PG&E, ask them to do the engineering work for the service upgrade. They will ask for the part number/brand, and location of the new service entrance device when doing the engineering work. Pay PG&E for the engineering work.
- Go to the city and open a permit for an electrical service upgrade
- Choose a trenching contractor and have them come out and start the trenching. Inform PG&E and the electricians when this work will begin (PG&E must inspect the work when they are done trenching and the electricians will need to start their work after the conduits are placed).
- After PG&E inspects the conduits, the trenching company will backfill the trench and then do a mandrel test.
- If your new service entrance will be in a slightly different location as the old one, the electricians can start installing the new service entrance device and some of the wiring for the new subpanels as the trenching company is working on installing the conduits.
- Coordinate with PG&E and the electricians. You need to find a day when both will be available; PG&E will come out in the morning to disconnect the power, the electricians will then install the new subpanel in place of the old panel, wire everything back up, and then you'll need to call PG&E when the electricians are done and have them come back out to turn the power back on.
- Schedule an inspection with the city to have them look over everything and finalize the permit

The trenching company I used seemed to have a pretty good relationship with the PG&E inspection team. In fact, I initially had the engineering team draw the diagrams for running the new conduit to the exact same spot where the old panel is located, but then changed my mind and decided that I'd rather have the new service entrance in a different spot, 6-7' further down the wall and on the other side of the gas riser (3' distance required between gas riser and service entrance). This would allow the electricians to put the new 200A subpanel in the same spot as the old main panel and reduce labor costs. I called PG&E and asked them about this and they said I'd have to send the project back to engineering and that there would be extra charges for this, but then I called the trenching company and the trenching company told me not to worry about it. They basically said "Remember those PG&E guys that showed up during our pre-construction meeting? Those are the guys we have to get approval from -- it's fine." They were right.

 

[jshutterbug]

Yes.

~$1950: PG&E engineering cost
~$6300: Trenching cost. Quoted $7000 for digging a trench to the PG&E box on the street. Got a 10% discount for paying cash. Used this company (although they CAN do trenchless construction, I used the open trench method). The other company I got a bid from was not competitive at all - they gave a quote for over $9000. The other option is to have PG&E itself do the trenching; this usually costs more than hiring an independent contractor.
~$8000: Electrician labor & supplies (new panels, breakers, install of Tesla WC, etc.)

Not a lot, considering the expenses associated engineering the project and having the trench dug just to put in the conduit. The trenching company's charges were not affected by whether I did 200A or 400A at all. The options were (labor + supplies included in both quotes):
- 400A combination service entrance device w/ integrated 200A subpanel for cars ($4000) + 200A subpanel for house circuits ($2500) OR
- 200A main panel and service entrance ($3500)

There were a few charges in the final bill that weren't in the original quote due to the price of copper surging, the fact that I wanted a whole house surge suppressor installed, etc. But overall, it was an extra ~$3000 to make sure that I never, ever have to pay $7000 for another trench. If the trenchers need to cross the street to get to the PG&E lines, this will probably increase trenching costs (and put the economics even more in favor of the 400A option).

My existing, outside-facing main panel and service entrance was changed to an inside facing 200A subpanel and the outside wall where the old main panel used to be was covered with new stucco; the panel itself is pretty much in the same location as the old one as therefore the electricians didn't have to move all of the wiring from one place to another (reduced labor costs). The new subpanel was connected to the combination service entrance device with wiring that can handle 200A.

Pretty much all 400A service entrances will not have a single 400A breaker, but will have 2x200A breakers right behind the meter (apparently because 200A breakers are much cheaper than single 400A breakers, and they don't really make 400A busbars for residential applications). There are also 400A service entrances without integrated subpanels, where you have two subpanels elsewhere. This may be better if you are, for example, converting your existing 100A panel to a 200A subpanel and adding a new subpanel for an ADU.

One option I considered, but didn't take, was to split the 400A into separate portions ahead of the meters (yes, two meters) so that I could have one rate plan for the house and another for the cars (PG&E EV-B tariff). The EV-B rates are better than the EV-A rates and would have allowed me to keep the house on a better plan for use of AC while still making vehicle charging as cheap as possible, but this would have segmented my service into two separate portions and I think in general, static partitioning is not good. If I were to have done 200A for the house and 200A for the cars, what happens if I later decide I want 250A for the house? Remember, PG&E can change the rates and there's no guarantee that EV-B will be better than other rates in the future, or that it will even continue to exist (Southern California Edison has in fact phased out their dedicated EV meter plan - no new approvals for that plan and I have not heard what they plan to do with people still on the plan in the long run). But this IS an option and when you are doing a service upgrade is the time to

I was not required to pay for this. Do you know how many houses are on the existing transformer? If yours is the only one, maybe you'd have to pay for it. If it's 2 or more, I doubt it. Underground transformers are typically either completely underground (you'll see a large (at least 3' by 6') covering in someone's yard that says "PG&E" on it) or they are large green above ground boxes that say high voltage/danger on them. If you drive around your neighborhood, you'll probably be able to see how many of these things there are, and estimate how many houses are on each one. And when you get the engineering drawing from PG&E, it'll let you know exactly which ones are on your transformer.

Yeah, I'm not exactly sure, but they charged me around $1950 for their portion -- inspections, running the new service lines, etc. There was around $450 in additional charges beyond the initial $1500 deposit. There was supposedly an allowance of around $1800 that comes from the PUC as well.

Since I had an independent contractor do the trenching, and I took the option of handling the permits with the city by myself (as opposed to having one of the contractors handle it, which would have cost more), I had to coordinate a whole bunch of activities. As you can probably tell, a project like this has a lot of "moving parts" and as the homeowner, it's your job to keep them moving. Overall, the process was like this:

- Contact electrician, ask for a quote on service upgrade. Get part number/brand of the service entrance device from electrician
- Contact PG&E, ask them to do the engineering work for the service upgrade. They will ask for the part number/brand, and location of the new service entrance device when doing the engineering work. Pay PG&E for the engineering work.
- Go to the city and open a permit for an electrical service upgrade
- Choose a trenching contractor and have them come out and start the trenching. Inform PG&E and the electricians when this work will begin (PG&E must inspect the work when they are done trenching and the electricians will need to start their work after the conduits are placed).
- After PG&E inspects the conduits, the trenching company will backfill the trench and then do a mandrel test.
- If your new service entrance will be in a slightly different location as the old one, the electricians can start installing the new service entrance device and some of the wiring for the new subpanels as the trenching company is working on installing the conduits.
- Coordinate with PG&E and the electricians. You need to find a day when both will be available; PG&E will come out in the morning to disconnect the power, the electricians will then install the new subpanel in place of the old panel, wire everything back up, and then you'll need to call PG&E when the electricians are done and have them come back out to turn the power back on.
- Schedule an inspection with the city to have them look over everything and finalize the permit

The trenching company I used seemed to have a pretty good relationship with the PG&E inspection team. In fact, I initially had the engineering team draw the diagrams for running the new conduit to the exact same spot where the old panel is located, but then changed my mind and decided that I'd rather have the new service entrance in a different spot, 6-7' further down the wall and on the other side of the gas riser (3' distance required between gas riser and service entrance). This would allow the electricians to put the new 200A subpanel in the same spot as the old main panel and reduce labor costs. I called PG&E and asked them about this and they said I'd have to send the project back to engineering and that there would be extra charges for this, but then I called the trenching company and the trenching company told me not to worry about it. They basically said "Remember those PG&E guys that showed up during our pre-construction meeting? Those are the guys we have to get approval from -- it's fine." They were right.

Thanks for the detailed explanation. Unfortunately, my existing service panel is <3ft from the gas meter so when I upgrade the panel, I will need to relocate the panel as well.

I was told 4 houses to each PG&E underground box.

Do you recall how much it was to split the meter? It would be nice for the ADU to have it's own meter but I think if split the meter, I wouldn't be able to have the Powerwall back up both homes during an outage. I guess I could keep one meter and install 3rd party meter to monitor usage on the ADU. If we ever decide to rent it out, the rent would probably be all inclusive anyways.

I'll reach out to the trenching company you used for an estimate (if PG&E can locate the box). Hopefully, they have a license to trench across the street. Did PG&E provide you a list of independent contractors or did you just call around?