Fronius ig series wastes energy at night

tampasolar Registered Users Posts: 65 ✭✭
I have 2 Fronius IG5100 grid-tie inverters. They both suck power in from the utility all night long. This time of year the pv system runs about 9 hours in the daytime, leaving 15 hours before start up the next day.

Using a clamp-on ammeter I have obtained the following values: (both systems I have assess the same)
Meter reading: 0.27 amp
.27a * 240v = 65 watts
65w * 15 hours = 975 watts wasted overnight on a system that produces 4000 watts in bright sunlight.
That's 12 cents a day per inverter ... for me $7.20 a month

Overnight waste is close to 25% of the hourly system capacity.
hybrid: xw6848 pro with two mppt60, 6 kw pv
17 cell 280ah LiFePO4 storage  14 kw
gridtie: sunny boy sma 2x 5k
gridtie: fronius ag5100 5k
Gateway / Insight Local
xw4548 backup


  • BB.
    BB. Super Moderators, Administrators Posts: 33,409 admin
    Re: Fronius ig series wastes energy at night

    Maybe, maybe not...

    Measuring just current on an AC system does not always represent power:
    • Power = Voltage * Current * Power Factor = V*I * Cosine (phase angle between Voltage and Current)
    Power Factor (and Cosine) always vary between -1, 0, and +1... Although, for many of the calculations and measurements we drop the +/- sign.

    So, what could be happening is you are seeing current that is going through the AC Filter Capacitors that are there to reduce radio noise in the inverter's output stage.

    With the Fronius, for the most part, turned off. The current you are measuring is possibly just to charge/discharge the capacitor... Which may have a Power Factor / Cosine near Zero... Which, in the power equation may reduce your actual power usage to near zero too (perhaps 1/2 or 1/3rd of that power you think you are measuring).

    Perhaps Fronius can give you some more information.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    Re: Fronius ig series wastes energy at night

    My pvp5200 pair draws 8 watts at night the power factor 40% And the kVA is 0.020. So perhaps BB is on the money.
  • drees
    drees Solar Expert Posts: 482 ✭✭✭
    Re: Fronius ig series wastes energy at night

    The Fronius IG5100 has been independently tested to draw less than 1W when off.

    As BB suggests, the power factor is probably very low when off.
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Re: Fronius ig series wastes energy at night

    Can't you just pull the breaker and clock the meter to see if it actually draws wht you think it does?

  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Fronius ig series wastes energy at night

    My fronuis manual list all the Ig series to use .15 watt on standby at night. The lg-5100 uses 15 watts consumption during operation. Fifteen hundreds of a watt is not much. :Dsolarvic:D
  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    Re: Fronius ig series wastes energy at night

    Late to the party, but just back up the regulars, the OP isn't using a DVM that measures power factor.

    Its a measurement issue, not a product issue
  • System2
    System2 Posts: 6,290 admin
    Re: Fronius ig series wastes energy at night

    You are all correct, the OP is simply seeing the still-connected output filter's reactive components pushing juice back and forth, with a PF near zero.