walterbays wrote:I think if SDG&E gets this requested increase we'll probably see a lot of batteries added to grid tied houses. Not the huge battery banks that would be needed to go completely off-grid, but just big enough to hold all of your daytime peak PV production to avoid sending a single kW back to SDG&E, and then use that energy at night to avoid drawing from SDG&E.
If you're a typical household where you don't consume a whole lot during the day while the sun is shining, you're going to need a much bigger battery pack than you think.
Even with my modest 3.24 kW system, I've exported as much as 17 kWh to the grid in a single day (not typical, around 10-12 kWh is more typical in the sunny months). Over the same time period, I've drawn up to 21 kWh from the grid. That excludes EV usage.
You're probably looking at least $500 / kWh for storage - never mind the efficiency losses involved with storage. I'm probably better off replacing my electric dryer with a gas unit financially at about $1000 if I'm looking to minimize my demand charges - that thing will suck down 3-4 kW for about an hour at a time.
Even if I could buy a 2 kWh household storage unit for $1000 - would it be smart enough to do peak load shaving in the face of highly variable single-household demands without running out of juice before my peak loads are done running?
walterbays wrote:Of course that tactic only works for homeowners who are net electricity consumers rather than net generators - something that owning a LEAF makes a little easier. Net producers would have to calculate whether they'd be better off selling their excess production for a pittance and paying a huge transmission cost to do so, or just dissipate it.
Net generators are already paid a pittance - it makes no sense financially to install a home PV system that generates more power than you use in a year.
walterbays wrote:Of course if everyone did that then SDG&E would need a lot of new generating capacity to replace that daytime peak production currently supplied by rooftop PV, plus new transmission capacity to bring it into the county.
Currently, not really. There's only about 35 MW of residential PV installed in SDG&E's region and about 37 MW of non-residential PV. SDG&E connects about 1 MW of residential PV a month - has maintained this rate for the past 2 years now.
Lots of data and stats here: http://www.californiasolarstatistics.ca.gov/
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