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What level of output should i be seeing..

Discussion in 'Tesla Energy' started by Tempus, Nov 24, 2020.

  1. Tempus

    Tempus Member

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    Question for the hivemind here. Just got done with the full process of getting my Tesla solar panels online, interconnect approved, etc..

    turned it on yesterday, so not a ton of data yet (half of yesterday, and this morning..)
    System size is the 16.32 kW, 48 panels. 40 of them on the south facing roof (front) The remaining 8 on the north facing (only place they would fit).

    Northern virginia area. This morning is fully sunny, not a cloud in the sky. I'm seeing a max of 4.6 kW in the Tesla app. That seems low to me for the size of the system. From reading up, it seems like in winter it should max at roughly half the system size... but i'm seeing closer to 1/4. Would love any input ...

    Thanks,
    Tempus
     
  2. jboy210

    jboy210 Supporting Member

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    Go to https://pvwatts.nrel.gov/ and enter your info. I would subtract the north size completly. Also, we are approaching the winter solstice, Dec 21, the day of minimum solar.

    And if you have any shading of the solar panels your yield may be dramatically decreased. My 12.75 kW solarroof went from seeing peaks of 10 kW to peaks of 1.5 to 2 kW because of shading. With daily generation dropping from 90+ kWh to 5-6 kWh. I can't wait for the leaves to drop from the trees shading the roof!
     
  3. SMAlset

    SMAlset Well-Known Member

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    Here in San Jose area at 10am clear sunny day we are getting 4.7kW on our medium system (11 SE facing panels, 13 SW facing panels; Q-Cell 340s). We’re fortunate in that our house placement on the lot is rotated 45 degrees from N. Kept tree placement away from house and only installed palms that would reach an average of 20-30 feet so no shading issues. Two story house.
     
  4. charlesj

    charlesj Member

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    A couple of tidbits of info. As mentioned, we are almost at the lowest sun arc across the sky, Dec 20/21. Weather is a big factor, of course.
    Then, system size. I think that 16.32 kW is the sum total of your panel size. If so, you will not see this quantity as the inverter size determines almost max out.
    Also mentioned, shading. Your north facing panels can be plugged into that website calculator, of course to see what that will produce.

    Now to your 4.6kW max. Since you posted or time stamped @ 9:09 AM, when was this total? Certainly not a full days of energy production that is in kWh. Check when the sun is straight up over your panels, or at end of day, move your cursor on only the solar reading to the peak for time and amount when that happens.
    Right now looks like I am at my peak and generating 2.7kW, 12:20, on a 3.8kW max system, clear, cool sunny day. Yes, temperature will affect production when panels go over 25C. Keep that in mind for the summer months. Also, that is not air temp but panel temp that you cannot measure. I can, and this summer I have seen temps approaching 50+C. I have Enphase inverters that can read panel temps or inverter under panel temp. Air temp was in low to mid 90F when that was read.
     
  5. getakey

    getakey Member

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    He's in VA, so that was noonish. It does seem a bit low. I have East and West panels and my peak yesterday was about 1/3 of total capacity
     
  6. BrettS

    BrettS Active Member

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    The OP is in Virginia, so while his post was at 9:09AM in California it was just after noon for him. A peak of 4.6kW on a 16kW system definitely sounds low, although I’m not sure how much your northern location will affect that. I have a 15.12kW system and I’ve been peeking at around 8kW at about 1PM. But I’m in Florida, so I would suspect that my system may generate a bit more than yours all else being equal.

    Is this a system with powerwalls or without powerwalls? And how many inverters do you have? If the system does not have powerwalls then the tesla app gets the production data directly from the inverter(s), so it is unlikely to be wrong. However, if you have more than one inverter then it’s possible that only one inverter is associated with your account on the back end, so you might only be seeing the production from a single inverter.

    If the system does have powerwalls, then the TEG has it’s own CT’s to measure solar production and it’s possible that a misconfiguration could cause it to read incorrectly.
     
  7. wjgjr

    wjgjr Member

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    I would agree with the suggestion of PVWatts as a first place to check. But I also think it does sound low. By comparison, just across the river, my ~8.2 kW solar roof, with 50% pointing north, maxed out at 3.1 kW today, with total production of 17.6 kWh (might add a couple tenths the rest of the day, but not much with the clouds rolling in.) This is what I would consider a near-ideal day for production around here at this time of the year - almost perfectly clear until like 30 minutes ago.

    Note that it may be an issue with production, but if you have multiple inverters, one may just not be reporting data. You might be able to check your electric meter or pull the data from your utility to get a sense of how much you were (hopefully) sending to the grid around noon, and see if that matches what Tesla is reporting.
     
  8. Tempus

    Tempus Member

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    Thanks for all the replies. As folks noted upthread, this was noon. Total production for the day is showing 25.5 kWh in the app. This is solar only, no powerwalls, and i have 2 inverters. Peak didnt change much, although there is a single spike up to 7.2 kW around 2pm. I was wondering if it was only showing single inverter data - ive seen other posts along those lines here. Just trying to determine if my output is reasonable for the system size and time of year for a sunny day before i try to engage tesla support
     
  9. getakey

    getakey Member

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    Your total seems about right. Doubling that would be way too much
     
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  10. wjgjr

    wjgjr Member

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    I don't agree that the total seems right, though doubling does seem like it might be a bit too much....

    Because I probably live relatively nearby to OP (who mentioned northern VA,) I am guessing we had similar sun today. I make a number of assumptions (which I admit is always a bit dangerous) and come up with a number of 52.2 kWh for the day. The assumptions include that the roof, like mine, really is mostly north/south, has no significant shading, and has a similar pitch (34 degees); that the panels have similar power generation profiles to my solar roof; and that PVWatts data on how much generation comes from the south and north roof faces is reasonable.

    I generated 17.7 kWh today from my 8.2 kW system. Using the numbers from PVWatts, about 15.24 kWh came from the south-facing roof and the rest from the north-facing, with my 50/50 split. This works out to about 3.72 kWh / installed kW for south-facing and 0.60 kWh/ installed kW for north facing. With OP having 40 340W panels facing south and 8 facing north, this multiplies back out to about 52.2 kWh.

    This is absolutely an estimate only, but I think that unless one of the assumptions is off (particularly on shading) the difference would probably be in the 10%-20% range, not over 40%. It is possible if one inverter is not running or not reporting correctly, it is the one that includes the north-facing panels, as 28.5 kWh is close to what 24 south-facing panels might produce (30.3 kWh is what I would have estimated.)
     
  11. BrettS

    BrettS Active Member

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    If the panels are not evenly distributed between the inverters and/or one inverter has all of the north facing panels then it’s definitely possible that the two inverters won’t generate the same amount of power. So it’s possible that if only one inverter is reporting then the OP is seeing less than the total production, but the total production wouldn’t be double what was being reported.
     
  12. getakey

    getakey Member

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    So with your analysis doubling would be almost spot on. Thanks for doing the math
     
  13. dcorb9906

    dcorb9906 Member

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    I am in northern California with 42 panels. Most are facing east and west but 8 are south facing. Your numbers sound about right as I had a max spike of 5.8 kW. Sun is setting and had a production of 37 kWh today with pretty much all sun and no clouds today.

    You can also request a Solar Edge account from Tesla (assuming you have SolarEdge inverter) to get detailed info down to each panel to make sure everything was installed correctly and is communicating.
     
  14. dhquigley

    dhquigley Member

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    Just to give one more data point, the guy across the street has almost the exact system of the OP, but faces East West mostly. We are just north of WJGJR. Today was my first day on with a slightly smaller solar roof, so we were comparing notes at noon (I was trying to figure out if my system was more efficient). In any event, at that time, he was pulling 6.1, which is about his peak this time of year. He pulled about 30 for the day.
     
  15. DrSmile

    DrSmile Member

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    I have 100% south facing panels (40 of them, 13.2KW) here in Northern NJ, with a fairly flat roof so my production dips significantly around this time of year (December production is usually 25% that of a Summer month). I still hit 10KW close to noon. Last year we had a pure sunny day on Winter solstice and I made 42KWh for the day. My 11.4KW inverter clips output almost 9 months of the year, but certainly not now.

    I think your app is wrong. Best thing to do is check the solar system meter at the beginning and end of the day.
     
  16. kpinthebay

    kpinthebay Member

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    Just checked my app. Today I got peak 3.3 kw at noon on my 4.75 system. 12 panels, all south facing, no shade anywhere near me in NorCal. Nice cool crisp sunny day. Had my PW charged from 10 to 100% before 1pm.
     
  17. tstolze

    tstolze Member

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    Not a Tesla system, but for comparison, 8 year old west facing 7.65 kW system, just west of St. Louis, MO.
    On a full sunny day, our system is producing just over 20 kWh's this time of year.
     
  18. charlesj

    charlesj Member

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    You must have hit it on the nail, inverter issue, how it is registering. He must have at least 2 inverters.
     
  19. charlesj

    charlesj Member

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    Interesting, comparing it to mine, although mine is all south and is a bit less than half of your total and almost the same for the south facing half. 2.7 kW peak and had 16 kWh total for today.
    Surprised how low your northern facing is producing although the sun arc is very low now for it.
     
  20. charlesj

    charlesj Member

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    I would agree with your assumptions and calcs what he should be getting. Yes, your northern panels barely see any sun with that 34 deg roof sloping the other way, 6in12 roof. Mine is 18 deg roof.
     

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