2 Solar/Powerwall installation options (poll)

[doubleohwhat]

Alright, I've done a bunch research and talked to both Tesla and SolarEdge. Basically there are two routes for new solar and powerwall installations and I'm not really sure which is best. So, I've created a poll and also welcome any thoughts or input. I'm describing these options as AC and DC coupled but please read the descriptions below for full details.

Note that I plan on installing two powerwalls. This is what makes the decision between these two configurations hard for me. If you need more than two powerwalls, it's an easy decision (go with AC coupled powerwalls).

DC Coupled:
Powerwall Type: DC (still available despite what some Tesla reps say)
Compatible Solar Inverter: SolarEdge StorEdge
Controller Interface: SolarEdge cloud interface. EX:

Pros:
More efficient - DC batteries charged from DC solar
Auto-transfer switch allows for only critical items to be powered when the grid is down. See diagram in attached PDF
Less hardware overall (StorEdge inverter does everything)
One interface for everything
Cons:
The StorEdge inverter only supports two Powerwall 2 units. This is only a partial "con" though. Additional powerwall units *can* added but they'll require separate StoreEdge interfaces. If you have a

AC Coupled:
Powerwall Type: AC
Compatible Solar Inverter: Any (from what I've been told). I'd go with micro inverters.
Controller Interface: Tesla App/cloud interface (no clue what it will be like at this point)
Pros:
Supports up to four powerwalls
Cons:
AC coupled powerwalls are slightly less efficient
You're relying on Teslas backup gateway into "tricking" grid-tied inverters into staying online when the grid is down.

Both the SolarEdge and the Tesla monitoring/control solutions will be cloud/app based. You *can* add a cellular modem to the SolarEdge inverter and the unit can be controlled from the inverter itself. I have no clue what the Tesla backup gateway will offer in terms of local control.

Thoughts anyone?

 

[doubleohwhat]

This thread can be deleted. After seeing some additional documentation the decision is easy.

 

[macbeth]

Can I ask what additional documentation you found to make this an easy decision?

 

[doubleohwhat]

It was the full installation manual for the SolarEdge StorEdge that had been updated for the powerwall 2. I received it from SolarEdge but I'm afraid I don't have it anymore. I deleted the email and the document after deciding not to go the DC powerwall route.

What I discovered was that while the StorEdge *can* be connected to two powerwall 2 units, it can only connect with one powerwall unit at a time. From the way it was worded, the StorEdge would charge or drain one powerwall and then switch to the other. Basically the thing seems to have been designed with a single battery in mind and then had support for a second battery added as an afterthought.

Also, the StorEdge supports a max of two batteries. That's fine if you only plan on getting two powerwall 2 units. However, what happens when the batteries in those units degrade to say 50%? To get back to 100% you'd have to replace *both* DC powerwalls. If you go with AC powerwalls, you can just add a new/3rd powerwall and go on your way.

Lastly, I was told twice by people at Tesla that while the DC version of the powerwall 2 is currently available, they will be focusing on the AC version going forward and that getting a DC replacement unit (if needed) in the future may be difficult.