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Integrating Existing Enphase with new panels and Powerwall

I have a current Enphase system with S280 inverters (they are not IQ compatible), system is 30x320W and broken up into 3 arrays. I wanted to make sure that my existing PV system will be able to charge the Powerwall (being that it is upstream from the Tesla Backup Gateway 2) in addition to the newly installed Tesla PV system. I've gone through the NREL estimates and it seems because of the pitch of my roof and panel orientation, I will need more than the 4.25kW of the new system to fully charge the PW on many days. I have attached the diagrams that Tesla had sent me.

Another concern I have is that if the grid goes down, will the gateway be able to control the S280 inverters to keep my house powered (I know it's either on or off and can't curtail based on usage and that if I pass 5kW to the PW or if the PW is at maximum capacity it will shut it off). Thanks in advance!
 

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Yes, the installers will put current transformers on the power wires from the array to allow the gateway to measure solar production. Off grid as the powerwalls charge, the gateway will raise the AC frequency, and the microinverters (e.g. s280s) will turn down their output to match what the powerwalls can absorb.
On grid, any excess solar above what the Powerwalls want or need just goes out to the grid.

However, your second posting shows only the new solar being used to charge the powerwalls. The old solar would be unused in any grid outage. Is that what you want?

All the best,

BG
 
Yes, the installers will put current transformers on the power wires from the array to allow the gateway to measure solar production. Off grid as the powerwalls charge, the gateway will raise the AC frequency, and the microinverters (e.g. s280s) will turn down their output to match what the powerwalls can absorb.
On grid, any excess solar above what the Powerwalls want or need just goes out to the grid.

However, your second posting shows only the new solar being used to charge the powerwalls. The old solar would be unused in any grid outage. Is that what you want?

All the best,

BG
Enphase had two S280 and mine is not the IQ, unfortunately.

About the second diagram, this is what I suspected, but when I reached out to my PA he assured me that I'd charge from the old system and be able to use them during a grid outage. I would like to be able to utilize my old panels to the fullest extent possible. I did have it in my mind that my old panels would be able to both charge and be used during a grid outage so if that is not the case, I am not sure if it is worthwhile to spend the money on this system.
 

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