On May 1, 2015, at 9:34 AM, via EV <ev@lists.evdl.org> wrote:

> While Lithium batteries make a lot of sense for vehicles where energy density 
> to weight is a big deal, I'm not sure of the advantage for stationary 
> installations.  Cost for Lithium is still a big issue.  An ~40kWh pack of 
> deep cycle, lead acid batteries that provide battery backup for my house 
> costs ~$5k.

Yes, but how long will those lead cells last? Indications are that, especially 
when gently used in climate-controlled settings, lithium batteries have the 
potential to have an usable service life similar to that of a mortgage, but 
lead acid batteries are notorious for going tits-up after just a few years. If 
you get five years from $5,000 of lead acid but fifteen years from $14,000 of 
lithium, the lithium is the better investment.

Especially if coupled with a generator or (PH)EV that can serve as a backup for 
extended periods of low input and high demand, and depending on the size of the 
PV array, a surprising number of people could drop off the grid with 20 kWh of 
batteries and many could with 30 kWh. Most should be able to with 40 kWh with 
many not needing the genset at that point.

If you're paying on the order of $15 - $20 / month for grid connection fees, it 
doesn't make sense to spend $10,000 or so on a battery to drop off the grid. 
But many utilities are trying to structure their rates such that, even if 
you're at or over 100% net generating capacity, you'll still cut them a check 
for $50 - $100 / month...and suddenly, hey-presto, that $10,000 to drop off the 
grid makes the same kind of financial sense that the initial solar investment 

Things are about to happen fast. Barring apocalyptic scenarios of whatever 
variety, most of us will live to see the day when a grid connection is as 
anachronistic as a landline telephone is today.

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