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Solar Question

Discussion in 'Energy, Environment, and Policy' started by apt0sr0b, Oct 31, 2013.

  1. apt0sr0b

    apt0sr0b Member

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    Aptos, CA
    Tesla owner. Changed my PG&E rate to EVA, at my billing cycle which was same time as delivery.

    Averaged 750kWh/month before the car.
    2 months in, and I am 1156kWh and 1200kWh.

    Thanks to EVA rate, my bill actually dropped by $70.00.

    My question is:

    If I use 1200kWh as my non winter usage, and look at my historical data seeing that I use 400kWh more December - February, that averages out to ~1300kWh/month.

    I am in process of getting 24 x 327W panels, and so if I do the math, maybe I should be looking at 26 panels.

    Anyway, I was thinking perhaps I stay with 24, and switch lights to LED, move the Hot Tob onto a timer, so its off-peak and partial peak on its cycles, etc. I might be able to stretch the 24 and wipe my bill, right?

    Thanks!

    Love this car!!
     
  2. derekt75

    derekt75 Member

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    You probably won't be able to wipe out your net electricity usage with 24 panels, but I think you should be able to wipe out your electricity payment. If you used to use 750 kWh/month all day long, then you can't be using more than 750 kWh/month during peak usage just because you bought an electric car that charges at night. 24 panels will average more production than 750 kWh/month, so you should be generating electricity at the day rate, and then consuming electricity at the night rate when you charge your car.

    I don't know how foggy your house in Aptos gets, and I don't know if your panels are facing South, but even without doing anything too extreme (like LED lights instead of CFLs), you might already be cost neutral.
    If it helps, in San Jose, I have a 5 kW system facing SW that generates about 8300 kWh per year, and a 6.2 kW system facing NE that generates about 7500 kWh per year.

    If I assume that Aptos isn't foggier than San Jose (probably a lousy assumption, but let's try it), and your system faces South, you're looking at 13 MWh of peak generation and 9 MWh of peak consumption, for a surplus of 4 MWh. That should cover your 6.6 MWh of car charging.

    Anyway, my calculations indicate that you should be a net consumer of electrical energy, but not of electrical dollars. I hope it works out for you.
     
  3. GlennAlanBerry

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    There are probably still a decent amount of changes you can make, such as using LED lights, using a NEST thermostat, getting some new Energy Star appliances, etc., to reduce your base electrical usage enough to cover your bill.

    Have you had an energy audit done on your house? Quite often, improving your insulation situation gives the most return on investment (but maybe not so much in California).
     
  4. apt0sr0b

    apt0sr0b Member

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    I have not. Anyone use any hot tub timers? My hot tub at the least will turn on every 12 hours. On EVA, that means off-peak and partial peak, but it would be great if there were 3rd party timers for nordic hot tubs. I mean, I know there are timers, are they easy to install and work, etc?
     
  5. derekt75

    derekt75 Member

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    Sure, depending on what your goal is.
    Since PG&E won't send you an annual check as a generator of electricity, it doesn't make financial sense to get your PG&E bill below $0. If you don't care about money, you can work to get your net PG&E usage to zero, but if you don't care about money, there's a lot you can do to help the environment. LED lights (compared to CFL lights) are probably not the most financially efficient way to save carbon emissions.

    Personally, I'd still vote to size your system to get your PG&E bill close to zero, and not worry that you're net PG&E usage isn't zero.

    OP: I don't know anything about standalone hot tubs. How often do you use yours? I only heat up the hot tub part of my pool before I'm going to use it, but I guess I don't use it that often.
     
  6. Lloyd

    Lloyd Active Member

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    Not correct.... In California PG&E does pay you, but only at a rate of .04 per Kwh.
     
  7. derekt75

    derekt75 Member

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    Good to know. Thanks.
    I still imagine there are more financially efficient ways to save carbon than LED lights if your marginal rate is $0.04/kWh.
     
  8. miimura

    miimura Active Member

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    Just to be 100% clear, PG&E only pays you for the portion that is net generation. It is possible to have a negative dollar annual bill and still not be a net generator. That negative balance will be wiped out when you start your new annual true-up.
     
  9. omgwtfbyobbq

    omgwtfbyobbq Member

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    LEDs and CFLs are really within spitting distance, and for the most part equal in terms of W/lumen in consumer settings.

    Maybe a hybrid water heater and a heat pump would save some cash, but that's about it.
     
  10. Grendal

    Grendal Active Member

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    I use a mixture of LED's and CFL's. My wife does not like the light delay that comes with CFL's so I use a combination of both to achieve the best results for her. LED's are 100% light immediately but cost a whole lot more than CFL's.

    My electric bill dropped dramatically without any regular bulbs.
     
  11. nwdiver

    nwdiver Active Member

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    The new CREE LEDs at Home Depot are AWESOME!! If you're ever in WA or know anyone there PSE pays for ~50% at the register. So you can get a "60w" LED bulb that only uses 9.5w and is virally indistinguishable from incandescents for <$6 :biggrin:
     
  12. MarkR

    MarkR Member

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    I would encourage everyone to think long-term and move to LEDs as soon as possible. We installed 28 panels at home, installed all LEDs, installed a solar hot water heater, and solar-assisted a/c. Our dual-pane windows save a lot and the extra insulation in the attic and walls is an important long-term investment. Outside tree placement and large overhangs on patio/veranda areas contribute a bit more to energy savings. As I move toward retirement, I want to eliminate my utility bill as I also rid myself of gas bills. Oh . . . one more thing. If you really want to maximize the return on your solar investment, just move to Arizona!
     
  13. RainmakerJL

    RainmakerJL Member

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    Can someone solar knowledgable point me to some info that will help me understand the benefit of doing it here in the north east?
     
  14. ggies07

    ggies07 Active Member

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  15. ecarfan

    ecarfan Well-Known Member

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    Interesting. If you live in a hot climate with heavy AC use than perhaps west-facing panels make sense. I do not, and don't have AC, so I think south-facing works fine for me.

    This text in the article caught my eye: "The next round of research will also include information about the pitch of the roof. Panels on flat roofs tend to have higher rates of electricity generation...".

    That does not make sense to me. Flat panels are hit by a lower density of photons than a panel at around the optimal pitch for the latitude of the installation.
     
  16. Robert.Boston

    Robert.Boston Model S VIN P01536

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    Most of us don't have the luxury of deciding which direction our house's roof faces....
     

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