TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker and becoming a Supporting Member. For more info: Support TMC
  1. TMC is currently READ ONLY.
    Click here for more info.

Inverter size when maximum system is 11.56 kW (34 panels)

Discussion in 'Tesla Energy' started by n.one.one, Mar 1, 2021 at 11:53 AM.

  1. n.one.one

    n.one.one Member

    Joined:
    Oct 12, 2014
    Messages:
    649
    Location:
    Metro Atlanta, GA, USA
    In Georgia to qualify for Georgia Power's monthly net metering the maximum system size is 10 kW AC. Tesla tells me that they will do a 34 panel, 11.56 kW system which will qualify. They have also said they will install a 7.6 kW Tesla inverter.
    • Will a 7.6 kW inverter limit the production that the panels would be capable of producing with a larger inverter?
    • Georgia Power 's tariff states the limitation as:"....residential applications with a peak generating capacity of less than or equal to 10 kW AC." and "The system’s AC peak generating capacity is determined by the aggregate nameplate capacity of the inverter(s) at the service point.".
    • Is Tesla's 7.6 kW inverter actually 7.6 or would the 'nameplate capacity' be less?
     
  2. h2ofun

    h2ofun Active Member

    Joined:
    Aug 11, 2020
    Messages:
    1,111
    Location:
    auburn, ca
    Yep, inverter limits system
     
  3. jrweiss98020

    jrweiss98020 Tessa's Tesla

    Joined:
    Jan 9, 2020
    Messages:
    382
    Location:
    Edmonds, WA
    Two things to think about:

    Is a larger inverter (e.g., Solar Edge 10 kW) available? It would be a shame to waste all that extra power in the summer...

    Can you go with fewer panels, so you don't have to pay for what you're not going to use? Granted, there is a balance between cost of more panels and optimizing production capacity for off-peak sun hours, but have you done that yet?
     
  4. nwdiver

    nwdiver Well-Known Member

    Joined:
    Feb 17, 2013
    Messages:
    7,360
    Location:
    United States
    The difference isn't as much as you would think. With a 7.6kW inverter and an oversize ratio of 1.5 the system will produce ~16,264kWh/yr. With a 10kW inverter you only gain ~200kWh/yr. With a smaller system size to reduce the oversize ratio to 1.2 with a 7.6kW inverter you lose ~3,000kWh/yr. Seems like a 7.6kW inverter oversized by 1.5 is just fine. Since Tesla is only going to have a 3.8 and 7.6kW inverter this is going to get A LOT more common. It will be interesting to see where they go from 3.8 to 7.6. 5kW? 6?.... 7?

    I've installed 2 systems oversized by 50%. The annual saturation losses are < 5%.
     
    • Like x 2
    • Helpful x 1
    • Informative x 1
  5. n.one.one

    n.one.one Member

    Joined:
    Oct 12, 2014
    Messages:
    649
    Location:
    Metro Atlanta, GA, USA
    I agree and found an article from 2016 that fully supports what you wrote. Why Oversizing Solar Panel Arrays Is A Smart Move
    After reading your reply and this article I ran my proposed system on PVWatts with a 1.52 DC to AC ratio vs. the 1.156 if I had a 10.0 Solar Edge inverter. The 10.0 inverter only generates 536 kWh more for the whole year at my location which is similar to your numbers.
     
    • Informative x 2
  6. nwdiver

    nwdiver Well-Known Member

    Joined:
    Feb 17, 2013
    Messages:
    7,360
    Location:
    United States
    Is your system ground mount or roof mount? PV Watts defaults to 'open rack' for some reason. Roof mount is ~200kWh/yr lower.
     
    • Informative x 1
    • Like x 1
  7. n.one.one

    n.one.one Member

    Joined:
    Oct 12, 2014
    Messages:
    649
    Location:
    Metro Atlanta, GA, USA
    There is so much to learn. Thanks for some great information. I've adjusted my PVWatts model accordingly.
     
    • Like x 1
  8. fragchild

    fragchild Member

    Joined:
    Nov 21, 2020
    Messages:
    12
    Location:
    Florida
    I also have an 34 Panel 11.56 system installed in December 2020. The gave me the default 10kW SolarEdge. If they're selling you 11.56 you should at least have the option to use as much of it as possible. ~200kWh/yr may not be a lot, but why not get as much as what you are paying for?
     
    • Like x 1
  9. nwdiver

    nwdiver Well-Known Member

    Joined:
    Feb 17, 2013
    Messages:
    7,360
    Location:
    United States
    #9 nwdiver, Mar 1, 2021 at 2:45 PM
    Last edited: Mar 1, 2021 at 2:50 PM
    Because the cost of upgrading to a 10kW SE inverter is ~$2,000 plus you'd need to do a line-side-tap since most distribution panels can only accept 40A (7.68kW) of solar. Even at $2k.... is $2k worth getting another ~$30/yr in production?

    Why not flip it? You paid for a 7.68kW inverter... should you not get the most out of it? ;) If it's only producing 6kW that's 1.68kW of inverter you paid for but you're not using.... max that baby out :)
     
  10. n.one.one

    n.one.one Member

    Joined:
    Oct 12, 2014
    Messages:
    649
    Location:
    Metro Atlanta, GA, USA
    From other posts it seems like they are no longer providing anything but the Tesla inverters...but I can ask. The Tesla inverter specs say it's 97.5% efficient while the SolarEdge spec sheet says theirs is 99.2%. Does that efficiency delta show up in real world results?
     
  11. nwdiver

    nwdiver Well-Known Member

    Joined:
    Feb 17, 2013
    Messages:
    7,360
    Location:
    United States
    The inverter is ~99.2% but the optimizers are also ~99% (0.99)(0.992) = 98.2% so the difference is really negligible.

    I'm really surprised they offered SE for as long as they did. Tesla is the lowest $/w installer and SE is among the highest $/w inverters at ~$0.40/w. I wouldn't be surprised of the Tesla inverters are <$0.10/w. That's a YUGE difference.
     
  12. fragchild

    fragchild Member

    Joined:
    Nov 21, 2020
    Messages:
    12
    Location:
    Florida
    For me I'd ask tesla to give me the big and the little inverter. Or drop some panels.
     
  13. nwdiver

    nwdiver Well-Known Member

    Joined:
    Feb 17, 2013
    Messages:
    7,360
    Location:
    United States
    I just want the most kWh/yr for the least $/kW.
     
    • Like x 1
  14. Alex_M

    Alex_M Member

    Joined:
    Sep 27, 2017
    Messages:
    12
    Location:
    Sherman Oaks, Ca
    Just completed a 32 panel 10.88 Kw install in February. Telsa installed a SolarEdge 10K inverter, but I am in sunny SoCal. It may be your location.
     
    • Like x 1
  15. preilly44

    preilly44 Member

    Joined:
    Nov 1, 2014
    Messages:
    459
    Location:
    Bethesda, MD, United States
    I'm getting a 35kw system and Tesla is trying to give me 3 of their 7.6kw inverters and one 3.8kw (for a total of 26.6). I'm not going to accept that. I want as little clipping as possible. At a very minimum, I want 4 7.6 inverters but I think I'd prefer four 7.6 and one 3.8.
     
  16. wwhitney

    wwhitney Member

    Joined:
    Nov 2, 2017
    Messages:
    731
    Location:
    Berkeley, CA
    If money is your limiting resource, then that's not an efficient choice. Go with the smaller inverters.

    If roof space is your limiting resource, and money is not an issue, then going for more inverters (lower DC/AC) is a good choice.

    If roof space is not your limiting resource, and you want more energy produced than you'll get from a 35 kW DC / 26.6 kW AC system, it's not clear whether you are better off adding more panels, or bumping up the inverter size. Probably more panels, but a more detailed analysis is required.

    Cheers, Wayne
     
  17. Two-rocks

    Two-rocks Member

    Joined:
    Jan 18, 2021
    Messages:
    79
    Location:
    gone
    Inverters are more efficient at the upper ranges of their output.
    You want a certain amount clipping, as it only happens at very limited times.
    The net result is more output from the 'system' without needless spending.
    The same nameplate company also sells FSD, and if you bought that you need to ask if you really care about a few cents here and there. :cool:
     
  18. Ampster

    Ampster Active Member

    Joined:
    Oct 5, 2012
    Messages:
    1,633
    Location:
    Sonoma, California
    I have a DC to AC ratio of 1.5 to 1 and see a little clipping. I still get the same performance from my 5.7 kW panels. It is important to remember that what counts is the area under the clipped curve not the area clipped. My curve starts earlier and ends later.
     
    • Like x 1
  19. nwdiver

    nwdiver Well-Known Member

    Joined:
    Feb 17, 2013
    Messages:
    7,360
    Location:
    United States
    With an oversize ratio of 1.32 for your location.... PV watts estimates saturation losses of 57kWh/yr..... that's 0.1%. Maybe you can ask for a 0.1% discount for all the energy you're gonna lose to saturation losses. ;)

    Also keep in mind that not all kWh are created equal. A kWh in TX during a blizzard is apparently worth $9... and there probably wasn't any inverter saturation occurring. A kWh produced between 11 and 3 on a nice sunny day in Maryland is probably worth ~$0... and that trend is increasing. Soon it will be worth less than $0.
     
  20. h2ofun

    h2ofun Active Member

    Joined:
    Aug 11, 2020
    Messages:
    1,111
    Location:
    auburn, ca
    I am doing it all wrong. I am putting in w SE 11.4K inverters. Just gives further growth if needed. Maybe not the most efficient, but,
    I like to oversize things
     

Share This Page

  • About Us

    Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.
  • Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


    SUPPORT TMC