how to measure amount of output from grid tie inverter?

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moesoo
moesoo Registered Users Posts: 10 ✭
in General Solar Power Topics #1
i am wondering how i can measure the output of a grid tie inverter that is connecting to the grid. what types of measuring devices are there? it would be nice to know how much i am pouring back in. thanks jer
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
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    Re: how to measure amount of output from grid tie inverter?
    moesoo wrote: »
    i am wondering how i can measure the output of a grid tie inverter that is connecting to the grid. what types of measuring devices are there? it would be nice to know how much i am pouring back in. thanks jer
    The best and simplest device is the power meter, just like your utility uses, although you can get less expensive ones which are not accurate enough to meet the regulatory requirements (not "revenue grade". Put it between your inverter and AC supply and you will be able to read the total energy transferred, and if it is digital, probably the power at the time you read it.

    Other alternatives include monitoring systems that connect to the wiring via current transformers and voltage leads and give you power and total energy over some period.

    Most grid tie inverters (GTIs) will include a way for you to read out the current power being produced and the total energy produced over some period too.

    If instead of the output of the GTI you really want to know what is going back into the grid, over and above supplying your own house loads, then a bidirectional utility digital meter which is installed by POCO when they approve your GTI connection can tell you that. That meter just cannot tell you what the actual production is.
    SMA SB 3000, old BP panels.
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  • moesoo
    moesoo Registered Users Posts: 10 ✭
    #3
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    Re: how to measure amount of output from grid tie inverter?

    thank you for the input. when they switched over to net metering here, i tried to get the old meter, but they wouldn't give it to me. where do you find those things? thanks jer
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  • Ethan Brush
    Ethan Brush Solar Expert Posts: 235 ✭✭
    #4
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    Re: how to measure amount of output from grid tie inverter?

    A regular utility type watt hour meter is probably the simplest and cheapest, only $60:

    http://www.aeesolar.com/products/ac-kilowatt-hour-meters

    Here are some current transformer types I have used before on some "sub metering" jobs. They can give you much more data and are available with split core CT's so you dont need to rework the GTI output circuit.

    http://www.ekmmetering.com/
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #5
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    Re: how to measure amount of output from grid tie inverter?

    Ebay has several firms that sell used meters. The meter bases can be purchased from Home Depot or Lowes. I bought one to measure my SRECS production which requires a "utility grade meter" I picked up a basic EKM meter last year, mine is dumb but was impressed with the kit. I would seriously consider getting an EKM in the future for monitoring.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #6
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    Re: how to measure amount of output from grid tie inverter?

    I have an extra meter that was my solar production meter until the utility came through and replaced it with a smart meter they can automatically read. It is a 4 lug regular meter, you will need to get a meter base to put i t in line but as it has been said before both the depot and lowes have them.

    The other way is to interface all the production and consumption with a TED, see link below for my setup.
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  • Wally
    Wally Registered Users Posts: 11 ✭
    #7
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    Re: how to measure amount of output from grid tie inverter?

    Hialeah Meter sells remanufactured Electric Meters that look like new. And at a very reasonable cost.

    http://www.hialeahmeter.com/siphwame.html
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  • moesoo
    moesoo Registered Users Posts: 10 ✭
    #8
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    Re: how to measure amount of output from grid tie inverter?
    solar_dave wrote: »
    I have an extra meter that was my solar production meter until the utility came through and replaced it with a smart meter they can automatically read. It is a 4 lug regular meter, you will need to get a meter base to put i t in line but as it has been said before both the depot and lowes have them.

    The other way is to interface all the production and consumption with a TED, see link below for my setup.

    i would have to say 'wow' to your ted. it's remarkable. too sophisticated for me. as for the meter, i have a base. when i had the standard elec. meter on my house, i could sometimes go and look at it and watch the little wheel in there going backward. also looking into what some of the others have suggested.
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  • jebatty
    jebatty Solar Expert Posts: 56 ✭
    #9
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    Re: how to measure amount of output from grid tie inverter?

    My POCO required a digital buy-back meter to be installed as part of the approval process. It only reads forward power from the PV into the grid. The electrician who installed my system recommended installing a utility grade meter to measure power output from the PV into the interrupt panel installed at the house. These two meters provide PV total output as measured at the house, buy-back power sold to the POCO, and total output minus buy-back = PV used by the house. A valuable additional benefit is that my micro-inverter PV system also measures total output of the array at the array collection point and instantaneous output via the software that also displays each panel's performance, faults, etc. The array is about 280 feet from the house, and I found that measured output at the house = 0.991 of output measured at the array, so slightly less than 1% line loss from the array to the house (or possibly +/- depending on the meter tolerance).

    I'm familiar with a number of other PV installations in my area, and all have software and meter monitoring. My software in addition to showing instantaneous output by panel and total output, also shows daily, 7-day, 30 day, 12 month, week to date, month to date, and year to date, and also provide a data download for each of these.
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  • ButchDeal
    ButchDeal Solar Expert Posts: 35 ✭
    #10
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    Re: how to measure amount of output from grid tie inverter?
    solar_dave wrote: »
    I have an extra meter that was my solar production meter until the utility came through and replaced it with a smart meter they can automatically read. It is a 4 lug regular meter, you will need to get a meter base to put i t in line but as it has been said before both the depot and lowes have them.

    The other way is to interface all the production and consumption with a TED, see link below for my setup.

    Have you thought about pushing your TED output to PVoutput.org instead of letting everyone hit your TED directly?
    Here is my TED output:
    http://pvoutput.org/intraday.jsp?id=31117&sid=28507
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  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    #11
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    moesoo wrote: »
    Re: how to measure amount of output from grid tie inverter?

    thank you for the input. when they switched over to net metering here, i tried to get the old meter, but they wouldn't give it to me. where do you find those things? thanks jer

    Well, it just happens right here http://forum.solar-electric.com/foru...atthour-meters , if member kansas still has them, and I imagine they'd be a fair price.
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #12
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    ButchDeal wrote: »
    Re: how to measure amount of output from grid tie inverter?



    Have you thought about pushing your TED output to PVoutput.org instead of letting everyone hit your TED directly?
    Here is my TED output:
    http://pvoutput.org/intraday.jsp?id=31117&sid=28507

    I was pushing stuff to plot watt but it too can overwhelm the little TED.
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