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Comment by amluto | Hacker News Reader

Having tried and failed to work with Tesla for solar, I strongly suggest you skip the powerwall. Use LG Chem’s RESU instead. It’s slightly cheaper, and they are willing to let third parties install it. It pairs with SolarEdge’s StorEdge.

If you want serious off-grid functionality, you need a beefier inverter. Outback sells such things, but the resulting system is a good deal more complicated.

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SolarCity installed the PV system, so I figured it'd be easier for them to continue with the upgrade. But it sounds like things are kind of a mess over in Tesla/SC land these days, so who knows...

Another factor is that the Powerwall 2 DC coupled model got canceled. And I don’t see how an AC coupled battery will give as reliable of a backup system without complicated integration with the inverter and without extra automatic switches that can isolate the battery from the loads.

In particular, how does an AC coupled system handle the case where the battery was fully discharged before sunrise? The inverter needs to turn on when the array starts producing, but the battery can’t charge without the backed up loads being powered, and the backed up loads can’t be powered until there’s enough battery charge to supply the inrush current.

A DC coupled system like the Powerwall 1, RESU, or pretty much any lead-acid system doesn’t have this problem at all.

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