Could solar panels provide another benifit?

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markf57
markf57 Registered Users Posts: 9
At the end of July, our solar panel installation was complete. August provided us with our first full month of production and the ability to match production to our utility bill. And the strangest thing happened. Our August usage factoring in both solar production and grid usage was down about 37% over the normal August usage.

What could have caused such a drop? Well, some could be related to our general efforts in conservation, but not 37%. Of course, one months data is not going to prove anything, but I do have an idea and I wanted to run it by this smart group.

Our system is 22 panels that virtually covers our south facing roof. We have 2 gables that prevents complete coverage, but for all practical purposes the south roof is full. I wonder if any of this 37% savings can be attributed to the fact that the radiant effect (or is it affect) of the sun not shining directly on the roof is keeping the attic cooler, which in turn is causing us to use less AC to cool the house? Sadly I did not monitor the attic temp before installing the panels.

Any comments?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,502 admin
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    Re: Could solar panels provide another benifit?

    Certainly very possible... My attic (uninsulated rafters, insulated ceiling) used to bake during summers... Now it is just a bit warmer than outside.

    But we don't have (or hardly ever need) A/C in our area.

    How hot is your area and how deep is your attic insulation... If your area has lots of temperature extremes--it may indicate that topping off the attic insulation (if possible) would be a good idea.

    Also, if you have duct work in the attic--Solar Guppy recommends just burying those in blown in insulation too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • markf57
    markf57 Registered Users Posts: 9
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    Re: Could solar panels provide another benifit?

    I'm in Colorado. We do have hot summers, August was very hot this year and of course cold winters.

    My insulation is around R-38, so I feel I'm ok in that department. No ducting in the attic either.

    Another thought was that the local utility did swap out the meter when I went solar. Maybe the old one was defective and reading higher than we were actually using. Does that ever happen?
  • vcallaway
    vcallaway Solar Expert Posts: 157 ✭✭✭✭✭
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    Re: Could solar panels provide another benifit?

    Attics not properly vented is a big deal. Everything from heat buildup to moisture and mold can cause all kinds of problems.

    Chances are your attic is not properly vented.
  • markf57
    markf57 Registered Users Posts: 9
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    Re: Could solar panels provide another benifit?
    vcallaway wrote: »
    Attics not properly vented is a big deal. Everything from heat buildup to moisture and mold can cause all kinds of problems.

    Chances are your attic is not properly vented.

    Sorry, I meant to say there is no duct work from the HVAC system in the attic. There are plenty of vents. Both eave and roof ridge along with a dormer vent.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,502 admin
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    Re: Could solar panels provide another benifit?

    In California, we are changing to "smart meters" and there have been thousands of complaints that the old meters registered less power usage than the new "smart" meters--Whether that is real or imagined is difficult to know.

    It is possible that the old mechanical meters read low (warn/sticky parts)--but I have not seen anything really documenting a wide spread problem.

    At this point, other than a few meters that were programmed incorrectly (electronic meters can be programmed for large services to read correctly when a "shunt" is used--The one mistake I read about was the meter was programmed to read 2-3x or something like that than was really being consumed--Mistake on the part of the utility programming for solar power billing).

    It is also possible that your family is now paying attention to the power usage--and cutting down on some usage too...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bryanl
    bryanl Solar Expert Posts: 175 ✭✭✭✭✭
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    Re: Could solar panels provide another benifit?

    re: "In California, we are changing to "smart meters" and there have been thousands of complaints that the old meters registered less power usage than the new "smart" meters--Whether that is real or imagined is difficult to know."

    I wonder if this has anything to do with how the new meters handle power factor?
  • russ
    russ Solar Expert Posts: 593 ✭✭
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    Re: Could solar panels provide another benifit?

    If your R38 insulation is at the roof line then there should be very little heat gain in the attic.

    That is more or less what I have and we get good summer sun here in Izmir. The AC has not been turned on the past two summers since the house was completed. On the hottest days I can comfortably take a nap in an attic bedroom with just natural ventilation.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,502 admin
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    Re: Could solar panels provide another benifit?

    As far as I know--No... They have not changed to kVAR billing with the new meters.

    It could be a case of bad timing (hot weather + rate increases), possibly old and inaccurate meters, and bad press (PG&E gets tens of thousands of complaints with new meters, San Deigo Power gets a handful of complaints).

    The articles you can find have frustratingly little hard information:
    An independent review of smart meters installed in Northern California by utility Pacific Gas & Electric found no technical flaws, but a poor roll-out with customers.
    ...
    Earlier this summer, the CPUC contracted with Structure, which tested 750 smart meters and 147 old electromechanical meters. The test found that smart meters reported accurately and that customer billing matched the expected results.

    Fortunately, we have the InnerTubes and we can get press releases online:
    Field meter testing was performed on 611 Smart Meters and 147 electromechanical meters, and included site verification, meter type and form factor verification, proper installation, and meter program and accuracy verification across six scenarios. The pass/fail criteria were based upon the CPUC accuracy standard of ±2.0% for electromechanical and Smart Meters. 100% of the 611 tested Smart Meters successfully passed the CPUC accuracy standard. Of the electromechanical meter field tests, 141 meters passed and 6 failed the CPUC accuracy standard.

    The entire report to the state CPUC is here (PDF Download--Note: 415 page report).

    It appears that the few complaints that were real--it was a hodgepodge of issues... Estimated Usage vs Actual Readings (power companies sometimes skip readings and catch up later), the issue of moving from lower tiers to higher tiered pricing (power rates $0.12 to $0.40+ per kWH as you use more power), changes in personal power usage, old meters were inaccurate, wrong rate plans, etc...

    Not to say that there won't be problems in the future:
    May 21, 2010

    Some of San Diego Gas & Electric Co.’s new smart meters turned out to be not so smart last week.
    They got confused during a software update, cut power to customers and stopped communicating with the company.
    The number that cut power is small, 33, all of them in Escondido, but SDG&E has decided to replace all meters installed around the same time.
    After replacing the meters that cut power, the company said Friday that it is now swapping out about 4,000 meters that have stopped communicating but are still providing electricity. It hopes to have that work done in the next couple of days.
    Then it will begin replacing the first 30,000 smart meters it installed, which have older software.
    “These are perfectly good meters — they’re measuring consumption — we just don’t want to take any risk of any more customer outages,” said Ted Reguly, who oversees SDG&E’s smart-meter operations.

    In the end, probably no systemic failure on the part of the meters to record power accurately for most people--But given the ability of computers (and companies, and government agencies) to screw-up in wild and wonderful ways--Never say never. :roll::p

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Hoonose
    Hoonose Registered Users Posts: 16
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    Re: Could solar panels provide another benifit?
    markf57 wrote: »
    At the end of July, our solar panel installation was complete. August provided us with our first full month of production and the ability to match production to our utility bill. And the strangest thing happened. Our August usage factoring in both solar production and grid usage was down about 37% over the normal August usage.

    What could have caused such a drop? Well, some could be related to our general efforts in conservation, but not 37%. Of course, one months data is not going to prove anything, but I do have an idea and I wanted to run it by this smart group.

    Our system is 22 panels that virtually covers our south facing roof. We have 2 gables that prevents complete coverage, but for all practical purposes the south roof is full. I wonder if any of this 37% savings can be attributed to the fact that the radiant effect (or is it affect) of the sun not shining directly on the roof is keeping the attic cooler, which in turn is causing us to use less AC to cool the house? Sadly I did not monitor the attic temp before installing the panels.

    Any comments?

    Could it be just as simple as your local weather? Average temps and humidity might have been down?

    For example here in Havasu we had a cooler spring than normal, and I finally went negative on our electric bills for a few months. For us the main factor is simply A/C time.
  • markf57
    markf57 Registered Users Posts: 9
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    Re: Could solar panels provide another benifit?
    Hoonose wrote: »
    Could it be just as simple as your local weather? Average temps and humidity might have been down?

    For example here in Havasu we had a cooler spring than normal, and I finally went negative on our electric bills for a few months. For us the main factor is simply A/C time.

    Actually, it was hotter and drier than normal last month.