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Powerwall Economics in Bay Area?

Powerwall Economics in Bay Area?

I can't figure out what the economics are for installing a powerwall or two. Has anyone done any analysis in the bay area as to whether this makes sense if you have solar, a tesla, and are on the EV TOU PG&E plan? I know that every situation is slightly different but would love hearing about anyone who has moved forward and why.

cwied | April 25, 2018

I don't think there's a way to make it look attractive financially unless you're really interested in backup. The restriction of charging only from solar in order to qualify for the ITC means you can't take advantage of the cheap overnight rates to charge up the powerwalls for use during the day. Furthermore, since the powerwall isn't eligible for net metering, you also can't offset more than your usage during the higher rate periods.

Financially, what you'd save is the difference between peak and part-peak on the usage from 2pm-9pm (minus 10-15% efficiency loss due to the battery roundtrip), provided your solar generates enough power before 2pm to cover that. You can discount the cost of the powerwalls by the 30% you'll get back for the ITC. That will give you your pay-back period.

I went ahead because there is a chance I can still get the SGIP and my inner survivalist likes the idea of a backup solution that can go indefinitely if the big one hits.

PatientFool | April 26, 2018

@cw_tesla i'm not familiar with the 30% ITC mention. What is that about? Assuming that you get both that and SGIP what would you expect your out of pocket costs to end up being on a powerwall?

cwied | April 26, 2018

The ITC is the Federal Investment Tax Credit - the 30% tax credit (see https://www.tesla.com/support/energy/own/powerwall/federal-investmenttax...).

If I get into step 3 of the SGIP, I will get $4060 back per Powerwall (I have 2). My installed cost was about $13,803, so SGIP would take my cost down to $5683. After the ITC it would be $3978. If I don't get the SGIP, the cost will be $9662. The problem is there is a huge backlog of Tesla customers waiting for SGIP and they may use up their allocation before it's my turn.

PatientFool | April 26, 2018

Thanks I hope that you get it. $4k our of pocket for two powerwalls is a nice deal