Would it be difficult to add a second Powerwall later?

[Carl_Drogo]

I'm ordering one Powerwall to start with. My energy usage is borderline. One might suffice, but two would be better. But it's a lot of extra money and I might be ok with just one.

Does it complicate things to add another one later if necessary? I know it means getting the crew out again and whatever is associated with that. Do you have to get permits? Am I setting myself up for more pain down the line or is it not a big deal to add another later?

Thanks very much

 

[Ampster]

I think it is easier because the Gateway doesn't have to be installed. The permit should be easier too.

 

[bemyax]

I'm ordering one Powerwall to start with. My energy usage is borderline. One might suffice, but two would be better. But it's a lot of extra money and I might be ok with just one.

Does it complicate things to add another one later if necessary? I know it means getting the crew out again and whatever is associated with that. Do you have to get permits? Am I setting myself up for more pain down the line or is it not a big deal to add another later?

Thanks very much

My single floor-mount Powerwall is recently installed. I've wondered this same thing about the money and capacity. The fellow who did the battery install encouraged me to add another saying all it takes is the Powerwall and a stacking kit. I didn't think to ask about additional permitting. I have the impression our electrical inspector is a stinker, to use a more polite word than he did.

 

[aesculus]

Tesla (if that is who you used) has a formula for each powerwall added to a system both initially and after. You can ask them for the prices.

I asked about the incremental costs of preparing my system for a 3rd powerwall when I installed the first two and they stated the extra cost that I thought was trivial so I did not bother to have it done initially. In my case it would have just been adding another set of conductors and the breakers and some config time. Since I was not really comfortable about needing a third one and they stated the difference I elected to defer the costs.

 

[zanary]

I had two Powerwalls initially, and I just added the 3rd which is the referral Powerwall. The installation process was easy, however all the same permits, PTO, inspections was needed. I'm in NorCal PG&E area, so the rules requires an NGOM from PG&E to be installed when you have more than 2 Powerwalls with Solar. NGOM (Net Generation Output Meter) is another meter that reports exact energy creation to PG&E and it's connected to your Solar Inverter.

No additional gateway is required, just another 30 amp circuit. Tesla also needs to make sure all your wiring from the load center to the gateway and from the gateway back to the main is of proper gauge, so there is additional work there on Tesla's part.

 

[bkp_duke]

If you were already doing a whole-house backup (i.e. 2 or more PW2s, most likely), then I would say adding an additional one later would be easy.

However, because you are just putting ONE in, the number of circuits you can put on it (i.e.a partial home load) is low, and that means when you add in the 2nd PW2 you are looking at a lot of substantial re-wiring (because the PW2s run in parallel, you would then have enough amperage to possibly backup a central AC unit, etc. which would never work on a single PW2 alone).

My recommendation, if you can afford it, do 2 at once. If your install, however, is big enough to do a whole-house backup from the get go, adding in additional PW2s later is relatively easy.

 

[Ampster]

'm in NorCal PG&E area, so the rules requires an NGOM from PG&E to be installed when you have more than 2 Powerwalls with Solar.

Are those the SGIP rules? Otherwise I am of the impression that no PG&E permission is required for batteries behind the meter as long as they do not send power to the grid.

 

[bkp_duke]

Are those the SGIP rules? Otherwise I am of the impression that no PG&E permission is required for batteries behind the meter as long as they do not send power to the grid.

It's a CPUC rule (to get PTO to put batteries in), and all of the major power companies in CA follow it. While the PW2 does not usually feed back to the grid, the solar system tied to it can, and both of them interact with the grid for frequency matching etc.

It's a SGIP rule to require a NGOM for "Large" installations (3 PW2s or more). I argued with SDG&E ad nauseam about it on our install because they could get the exact same data from Tesla from the gateway. They didn't care, they wanted their own meter.

I believe I read in the latest SGIP rules that has been changed to an even larger installation size, but that was a quick pass read, and I'm not 100% sure on that.

 

[bob_p]

A single PowerWall can be mounted on the wall, elevated off the floor.

For our 4 PowerWall configuration, we have two stacks of 2 PowerWalls mounted back-to-back on the floor.

If you're considering adding more PowerWalls in the future, would recommend you have the first PowerWall mounted on the floor, because adding a second PowerWall to the front is easy, using the same conduit for cabling as the first PowerWall.

The Tesla Backup Gateway can handle up to 10 PowerWall 2's.

 

[Ampster]

It's a CPUC rule (to get PTO to put batteries in), and all of the major power companies in CA follow it. While the PW2 does not usually feed back to the grid, the solar system tied to it can, and both of them interact with the grid for frequency matching etc.

I pulled a building permit for an Outback Skybox and there was no mention of the need for a PTO. I scoured the PG&E web site and the Civil code and found nothing. Since I am not regulated by the CPUC, I don't think they can tell me what I have to do. I am not arguing with you but have a sincere desire to understand. I have asked this on several forums and not received a definitive answer.
I am of the impression that the same holds true for a generator. The assumption, of course is that neither send power back to the grid and that no SGIP money is involved.

 

[bkp_duke]

I pulled a building permit for an Outback Skybox and there was no mention of the need for a PTO. I scoured the PG&E web site and the Civil code and found nothing. Since I am not regulated by the CPUC, I don't think they can tell me what I have to do. I am not arguing with you but have a sincere desire to understand. I have asked this on several forums and not received a definitive answer.
I am of the impression that the same holds true for a generator. The assumption, of course is that neither send power back to the grid and that no SGIP money is involved.

If there is no SGIP money, and your utility doesn't have the NGOM requirement, then you will likely be fine.

SGIP and my utility, however, had strict requirements for anything over 2 PWs that an NGOM was required.

 

[wwhitney]

This article says that the NGOM requirements for solar plus storage recently changed or are changing:

CPUC Approves Energy Storage Net Metering

I haven't read through the CPUC decision, and I don't know the progress on the IOUs implementing it.

Cheers, Wayne

 

[woferry]

I only have a single PW (with whole-house backup) and do plan to add a second one later (once household power consumption increases, most likely due to adding AC), but my PG&E interconnect form was for storage of up to 10kW (inverter capacity), which suggests there's a different one for storage above that. I don't know what's different on the different form however, and what extra rules come with it, so I can't offer any help there. It shouldn't affect my install at least.

So have people gotten past the CA code changes that started in 2020 that were supposed to make more than 1 PW much more challenging? Not as bad as some threads on here feared? Or still too early to tell?

 

[Ampster]

If there is no SGIP money, and your utility doesn't have the NGOM requirement, then you will likely be fine.

Thanks, that clarifies it.
In my research I discovered that only the three IOUs are regulated by the CPUC. None of the municipal utilities are regulated by the CPUC. Also since a lot of Powerwalls were installed without SGIP money, those would not be regulated. I am in the PG&E territory affected by PSPSs and a lot of people in my area are just looking for backup and that is one less hoop for them to jump through

 

[Ampster]

This article says that the NGOM requirements for solar plus storage recently changed or are changing:

I guess if I wanted to get credit for storage sent to the grid I would have to get a PTO.
While I am not generally a fan of more regulation this would be a good thing for the resiliency of the grid. This may also be the economic incentive that would cause me to take that extra step.

 

[charlesj]

If you decide on one PW and another later, make sure there will be room for another 30A breaker in the backup loads panel.

 

[woferry]

I'd also suggest making it clear to the install crew. They may not make major changes, but I think they can at least keep it in mind. Mine told me that all they'd have to do was replace an elbow with a T and use the existing conduit they ran for the first PW to wire-up the second one, even though they won't be stacked. They were also going to center the PW on the wall segment I'd chosen, but I got them to push it off to one side to leave room for a second one next to it.

 

[bkp_duke]

When we had our 3 PWs installed, I asked them to pre-wire for a 4th. They did this with no problem, and now when we are ready for that 4th one all I have to do is mount the PW2 on the wall, install a breaker, and have Tesla provision it in the software.

 

[jboy210]

First, my 2 cents is the fewer times the city/county has to send out to inspect the installation the better. Having been in continuous remodeling mode for the last 5 years it is a real crap-shot as to what some inspector will flag. A lot of interpretation.

Second, the additional cost of the second PW will be considerable below the cost to add the 1st PW. And you could do like bkp_duke did and have them wire it for the 2nd power wall so they ensure there are no structural/wiring issues

 

[jboy210]

...
So have people gotten past the CA code changes that started in 2020 that were supposed to make more than 1 PW much more challenging? Not as bad as some threads on here feared? Or still too early to tell?

I think it is a little early to know for sure, but installations with 2 or more powerwalls seem to moving along. Mine is set to start by the end of the month and all our paperwork is dated 2020, so we will see.

It may, as some have pointed out, be something were the homeowner installation of the unit trumps the fire code provision which seems more aimed at commercial installations. At least I sure hope it is.