On 7/14/19 11:28 AM, Robert Bruninga via EV wrote:
What you described seems to be a net-metered system. You are buying and
selling power to the grid. You produced say 10,000 kWh and you bought
10,000 kWh. For a NET energy payment to the utility of zero. The goal of
any home solar system.
I guess we have a clear writing problem on my end. Or, maybe a
comprehension problem on yours. Or, maybe some of both.
I tried to say that I am buying almost no energy from my utility and I
am selling them quite a lot. The overhead or connection fee is about
$25/month so, at $.06/kwh which is my selling price, I have to give them
about 600 kwh per month to reach a zero bill. Right now, my monthly
net bill is a credit of about $100/month. I'm hoping to eventually get
that up to several hundred dollars per month.
So that is what net metering is all about. So... What value then is the
battery? It adds nothing to that equation other than a fixed $13,000 up
front loss that can never be receoverd.? What am I missing?
The battery is of minor value while the grid is up. Without the
battery, I would be buying about 10kwh per night and paying about
$.10/kwh. Then, during the day, selling back at about $.06/kwh. So,
the net benefit of the battery in my situation is probably less than
$1/day. Certainly less than $2. It WOULD take me far longer than the
life of the battery paying for it at less than $1/day.
Since the utility is willing to pay cash for over production, I may well
have an unusually good deal.
I bought the PowerWall primarily for grid down security but find it
useful for a little day/night savings.
You have described a PowerWall. The battery is one or more units that
will supply or charge 5kw and holds 13-14kwh. If about 11kwh will carry
you over night and if you don't use more than 5kw over night, a single
battery unit will serve you. With good sun, day time self power use can
be around 20kw, including car charging.
In 5 or so months, I have bought less than 10kwh from my utility and
sold them something like 10,000 kwh. That is with one battery unit.
Cost installed was about $13k. For smooth operation, I am highly
dependent on the utility to accept my excess power.
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