Things to ask Tesla before accepting the system design

[Docfxit]

I'm planning on asking these questions before I accept the system design:

1. Are both (I have 2-Powerwalls+ in the design) model 158000 - 7.6kW?
2. What is the DC to AC ratio?
3. I'd like to see the Plan set.
4. Can I get panel edges on all 4 sides?
5. Will I get two inverters? I don't want to see clipping. (I'm looking at an 11.6kW system)
6. Will they wire the panels so I can charge my car from solar?
7. Will they put the car charger on the backup side. (I know it will be. I just want to make sure they know I have a car so they add a CT to monitor it)
8. Will I be able to send extra PV power to the EV while on Grid?
9. Will they install a CT on the Wall Connector?
10. Will I be able to charge the car with excess solar while grid power is out? (I've seen the link that explains this. Things change all the time. I'd like to ask)
11. Will they install one 20amp 110v outlet on the grid side so I can know when the grid is down? (And charge my car if the PV fails for some reason)
12. Will they run the wires through the garage and into the attic so there will be no EMT conduit on the outside of the house?
13. Will they install the powerwalls inside the garage?

Is there anything else I should be requesting / upgrading with Tesla?

 

[jgleigh]

#6: Think of solar like another power source. The power goes where it is needed.
#7: No CT needed if it's wired on the backup side.
#8: Yes
#9: Not needed if #7 is true.
#10: Yes if #7 is true.
#11: Are you asking them to install an outlet or leave a circuit non-backed up? The app will tell you if the grid is down. If the PV fails, then your car would charge from the grid.

 

[Docfxit]

Jgleigh: Thank you for the wisdom:

#6. Someone else on TMC said they couldn't charge their car from solar during a power outage and they had a powerwall.
#7. If there is no CT the energy app won't know about the car. I read the Wall Charger needs a CT for the energy app to recognize it.
#8. How does everything on the backup side know to prioritize the power coming from the PV over the grid?
#9. How does the energy app show me the car is getting power from the PV without a CT?
#10. Someone on TMC said the answer is no. I don't see why they said no. As long as a powerwall is working it seems to me everything on in the house including the car should be able to be charged from the PV. I just need to make sure if the PV is not putting out the car stops charging. I can do that with my home automation.
#11. I need a power plug that will not have power when the grid is down so my home automation will know when the grid goes down. I want my home automation to turn off the A/C and the charging of the car. Some how I think the car will stop charging by itself. I do want to be alerted so I can plan to go to a supercharger if the need arises. Currently I do get messages on my phone from the Tesla app but I don't get a notification sound. I have tried all kinds of settings but I can't get my phone to give me a sound from the Tesla app. I can from my home automation.
#11. If for any reason the PV and the powerwalls need to be shut down, I want one 110v outlet to charge the car when I have grid power.

With all the people in this forum that have had PV installed, I thought for sure someone would come up with something that I haven't thought of to ask for, relating to a PV installation.

 

[jgleigh]

#6: If the EV charger wasn't on the backup side, then it wouldn't work during a power outage.
#7: Anything wired on the backup side is automatically monitored by the CTs built into the Gateway. If it's wired upstream of the Gateway then you'd need a CT somewhere else (main panel or sub panel or load circuit).
#8: Power is power. You can control how fast the Powerwalls charge, but normal loads on the backup side just use power that is available. You can't direct PV power vs grid power. It just goes where it is needed. The Gateway will adjust Powerwall charging to minimize grid usage since it has control over those loads.
#9: Like I said, if it's on the backup side it's already monitored by the Gateway.
#10: I think you're confusing on-grid and off-grid. Off-grid, the Tesla app can control how much power is going to the car during a power outage. You set a Powerwall minimum level before it cuts off car charging. On-grid, you have to use something like ChargeHQ currently. Tesla is rumored to be adding similar functions in the future.
#11: The reason I asked is Tesla is setup to do cookie-cutter installs. They usually don't handle custom requests, but you can always ask. I think your idea of using a grid-tied plug to trigger your home automation will probably work. Regardless of this though, your existing plugs will work just fine regardless of PV and Powerwall. You can shutdown the whole system and your house will just run off grid power.

 

[Matt-FL]

#12 - yes, but it needs to be part of the design. I requested the PWs to be installed in my garage, which Tesla calculated at about $1200. They ran all the solar panel wiring through my attic to the meter side of the house (gateway, inverters and cut-off are installed next to the meter). I was able to actually reach their designer and have a discussion with them. I provided pictures and measurements to them.

#5 - I'd suggest requesting a second inverter - it will increase the price if they didn't plan for two. I wish I had three - 20.4kw system with only two inverters. I see a max of 17.2kw production. One of those 'wish I had known, but nothing to do now'.

 

[Docfxit]

#12 - yes, but it needs to be part of the design. I requested the PWs to be installed in my garage, which Tesla calculated at about $1200. They ran all the solar panel wiring through my attic to the meter side of the house (gateway, inverters and cut-off are installed next to the meter). I was able to actually reach their designer and have a discussion with them. I provided pictures and measurements to them.

#5 - I'd suggest requesting a second inverter - it will increase the price if they didn't plan for two. I wish I had three - 20.4kw system with only two inverters. I see a max of 17.2kw production. One of those 'wish I had known, but nothing to do now'.

Thank you very much for the feedback...

#12 - I requested it be installed in the garage. They want to wait for the site inspection to say yes. They haven't said anything about $1200. They did say I might have to install sprinklers and posts so the car can't bump into them. Did you have to install those?

#5 - I have confirmed with them they are including two inverters. Two powerwall + (each with an inverter) and one powerwall 2 (without an inverter). 11.6kW

Do you have any powerwalls? I'm guessing you have net metering 2. I'm thinking powerwalls aren't as useful with NM2. I haven't placed the order yet so I will get NM3. I'm thinking the 3 powerwalls will save me more so I have less electricity to buy.

 

[Matt-FL]

I have four Powerwalls installed in my garage, in stacks of 2. I did not have to install posts, but I'm in Florida and the rules might be different. We tend to cowboy it a bit more than California, probably why so many people are moving here.

I'm on my local utility plan, which is selling back at 'fuel cost' rather than full transmission charge. When I did my ROI, it was based solely on reducing my bill down to close to zero. I've actually accomplished that, and since my utility is also my water and sewer provider, what I sell back covers my connection fees + part of my water bill. My bills were in the $450 range, now they are down to ~$70 (that's electricity, water + sewer).

My Powerwalls are setup in self-powered mode. I have them set to 100% self-powered, but I adjust if a storm is coming.