What wiring needed 4Powerwall in detached garage 2 back up a house located 20' away?

[Ampster]

Tesla seems to have thought out the cookie cutter approach to drive costs down. I have heard of a few instances where the DC capacity was able to be tweaked based on site specifics. I have not heard how the new Tesla inverter choices may influence that flexibility. At those prices i would be in favor of using an agressive DC to AC ratio if I were to get a proposal from Tesla.

[oregon_phil]

Inverter sized to prevent 100amp and 200 amp panel upgrades totally makes sense. Thanks for the reminder.

[PVAndy]

It just says Powerwall, 13.5kWh capacity. I agree the generic query would recommend a low DC watts per powerwall to get sales up. Interestingly enough, the Tesla string inverters are sized 3.8 kw and 7.6 kw.

13.5 kWh is storage capacity. 3.8kW & 7.6kW are sized to allow a backfed breaker into a 100A(100A Buss) & 200A(200A Buss) panel without having to do any panel upgrades or lineside connection,.

Tesla recommends both max DC and AC per Powerwall. Max AC power per Powerwall is 7.6kW

Andy

[oregon_phil]

It just says Powerwall, 13.5kWh capacity. I agree the generic query would recommend a low DC watts per powerwall to get sales up. Interestingly enough, the Tesla string inverters are sized 3.8 kw and 7.6 kw.

[Ampster]

....... For every 4.05kW DC of panels, they recommended 1 Powerwall. Looks pretty basic. Nothing is said about inverters.

I can believe that as a generic recommendation for an online query. That ratio would be good for selling Powerwalls. I have seen some figures from other hybrid inverter manufacturers that distinguish between older UL 1741 AC coupled inverters and newer UL 1741SA inverters. Ultimately the Powerall is interfacing with the GT inverter on the AC bus, not the panels on the DC bus. At least that is how my Skybox defines the interface.

[SunEagle]

I ran the tesla quote machine on the web. For every 4.05kW DC of panels, they recommended 1 Powerwall. Looks pretty basic. Nothing is said about inverters.

Is that calculation for the Powerwall or Powerwall2? I believe they are different animals.

[oregon_phil]

I ran the tesla quote machine on the web. For every 4.05kW DC of panels, they recommended 1 Powerwall. Looks pretty basic. Nothing is said about inverters.

[Ampster]

....what does Tesla recommend 6kw of solar panels per Powerwall2 battery setup?

Your question reminded me of another detail that might need clarification.
Is the maximun capacity of AC coupled solar per Powerwall based on the AC inverter capacity or the DC solar panel capacity?

[khanh dam]

The reason I brought up the need for 2 Powerwalls has to do with max solar that can be connected to a Powerwall. You could split up the micros and use some to charge Powerwall during a grid outage (connect to gateway) and connect some to line side of gateway so it turns off during grid outage.
Andy

Thanks what does Tesla recommend 6kw of solar panels per Powerwall2 battery setup? Is what I have seen, does that seem correct?

[Ampster]

The reason I brought up the need for 2 Powerwalls has to do with max solar that can be connected to a Powerwall. .....

Yes, that is an important aspect of system design especially for AC coupled systems. I do not know if the OP has a working knowledge of those parameters. Unless he has a Tesla authorized installer like yourself providing him input the only thing he or his customer would need to worry about is what loads to put in a critical loads panel subject to the limitations that you have already discussed.

[PVAndy]

You and your customer could spend your time more productively thinking about which loads to back up and not worry about the topology of the wiring. Those would be the loads that are swung to the critical loads panel. For simplicity that location would most likely be near where those loads enter the panel.
The larger elements of gateway and Powerwall connection is what your customer is paying Sunrun or Tesla to do as part of the installation process. I am sure you will get a design to approve before construction starts if you want control over that element.

The reason I brought up the need for 2 Powerwalls has to do with max solar that can be connected to a Powerwall. You could split up the micros and use some to charge Powerwall during a grid outage (connect to gateway) and connect some to line side of gateway so it turns off during grid outage. We have designed several hundred Powerwall installs and had problems early on with too much solar. Tesla has revised guidance based on experince

Andy

[Ampster]

You and your customer could spend your time more productively thinking about which loads to back up and not worry about the topology of the wiring. Those would be the loads that are swung to the critical loads panel. For simplicity that location would most likely be near where those loads enter the panel.
The larger elements of gateway and Powerwall connection is what your customer is paying Sunrun or Tesla to do as part of the installation process. I am sure you will get a design to approve before construction starts if you want control over that element.

[khanh dam]

.......
Tesla just announced that they are restricting Powerwall sales to projects which include a Tesla solar installation.

they actually still sell the batteries to other solar companies like SunRun and I'm pretty sure sunrun installs the battery and not tesla. SunRun's price is about 2x for the tesla battery vs buying direct from Tesla. But like you said I think Tesla wont' sell direct to the customer a battery alone.

[Ampster]

what is the best way to wire up this situation?

.......
Let Tesla worry about that. They have done thousands of installs. Their price is the most competitive anyway.

[khanh dam]

Minimum of 2 Powerwalls required with your size sysetm. Each Powerwall is 30A so if combined would require #6 wire. Both house and garage can be backed up by Powerewalls

Andy

customer can only afford one power wall, might buy a 2nd latter on. what is the best way to wire up this situation?