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Thread: Non-Net Metered PV system- Grid Tied

  1. #1
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    Non-Net Metered PV system- Grid Tied

    I am in the process of designing up around a 25kw pv system and customer may want to expand in the future. Current Utility standards state that there can only be 1 net metered facility per parcel of land. In my design I am trying to come up with a cost effective way to track the current on the Line side of the main disconnect so that if the PV system were to ever try to "sell back" the power the CT's would trigger a Contactor on the Combined output of the solar before the interconnection point and turn the system off. Additionally I want to make sure the system can be turned back on automatically when this situation is no longer in play. Has anyone run into this before? any insight would be greatly appreciated.

  2. #2
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    So essentially a reverse power relay?

    Will the utility let you backfeed them but without net metering? So just give to utility free power to avoid the reverse power relay?


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  3. #3
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    Quote Originally Posted by pcanning87 View Post
    So essentially a reverse power relay?

    Will the utility let you backfeed them but without net metering? So just give to utility free power to avoid the reverse power relay?
    That's what I was thinking. Does the utility prohibit backfeeding in this case, or is it just because doing so makes no money for your customer? If the latter, why does the customer care? Giving it to the utility and turning off the system have the same effect to the customer (it's not like he is saving any money), and gear like you are asking about costs money.

  4. #4
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    no. I was told I need to put in contactor(s) and relays so that the system will NEVER back feed.

  5. #5
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    Quote Originally Posted by bwaryjasz View Post
    no. I was told I need to put in contactor(s) and relays so that the system will NEVER back feed.
    So, I repeat my question: why?

  6. #6
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    GGUNN I just sent in an RFI to the Utility company to ask this very question again. I completely agree with you, a loss of PV output is a loss of PV output to the customer. whether the system is off or the power is just "given" to the grid.

  7. #7
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    Might have to do with the Metering of said power. if they change out the meter to the Typical Net meter that tracks imports and exports. the billing would be a nightmare. then if they didn't change out the meter the customer would be getting charged for the power they are exporting.

  8. #8
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    It could also be an issue with the capacity of the utility feeder line to handle Distributed Generation. If you never backfeed the grid, it may alleviate technical issues on the utility side.

    That said it seems more likely that it's a commercial/Metering concern like bwaryjasz said.


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  9. #9
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    Quote Originally Posted by pcanning87 View Post
    It could also be an issue with the capacity of the utility feeder line to handle Distributed Generation. If you never backfeed the grid, it may alleviate technical issues on the utility side.

    That said it seems more likely that it's a commercial/Metering concern like bwaryjasz said.


    Sent from my iPhone using Tapatalk
    AHJ's frequently designate a "downtown network" where no one is allowed to export to the grid at all, no matter what. To the OP: is this such a situation?

  10. #10
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    I understand that this is a common problem in Hawaii wherein the grid can not accept more PV input at this time. I attended a Solaredge presentation that showed they have a metering option that communicates to some of their inverters and eliminates backfeed to the utility. No direct experience.

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