http://www.teslamotors.com/powerwall

So there was a lot of hype about this the other day, and I didn't know if it needed to go in the home ownership thread or its own, but it wouldn't get a whole lot of foot traffic in the other thread.

I called Duke Energy Progress to see if they are going to be supporting any rebates and they didn't know. I guess it is still too new. My biggest concerns are...would the battery last long enough to recoup a 25% savings in my energy bill? And I'm not even sure if Duke Energy Progress changes their kWh rates by default - I think that is a program you have to sign up for.

So my average bill is about $200/month. That's $50/months savings, and at that rate it would take almost 6 years to pay it off (cost is $3500). Tesla guarantees them for 10 years, but I don't know...a lithium ion battery lasting 10 years seems to be a stretch.

Anyone else interested in these?

5/7/2015 3:27:13 PM

Doesn't matter if it does not last 10 years. Tesla will replace it.

The real wrinkle is that it's limited to a 7 kWh daily cycle. At the usage rates you're talking about you'd need multiple units. Some back-of-the-envelope math puts a $200 per month power bill around the 40 kWh per the part of the day in the peak usage window.

Math:
$200 ~= $190 per month of metered power
30 days = $6.33 per day
@0.093 $/kWh (residential non time of day dependent rate) that's ~= 68 kWh/day.

My take of these is that without an accompanying solar installation, they're not cost effective.

[Edited on May 7, 2015 at 3:56 PM. Reason : more info]

5/7/2015 3:54:28 PM