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I was wondering if anyone with a string inverter had the curiosity of checking the actual efficiency.
What I mean by efficiency is AC power coming out of the inverter divided by the DC power going into the inverter.
Here are the measuring method I used.
DC in:
I have separate panel monitoring (optimizers), so I can get the DC in in two places, directly at the array with the optimizers reporting, and from the Inverter solar production. I have already found the Inverter number to be on average 0.9% below the array, which I assume are the line losses.
Note: If the only report of the solar production comes from the inverter one would need to be sure of where they measure it.
AC out:
For the AC coming out, I figured the best way to be sure of that is to turn off ALL the house breakers, leaving just the Inverter breaker on, and measure the Grid Export. That should give me the actual AC power the inverter creates from the Solar input. The grid export can be taken from the grid monitoring reading if its accuracy has been verified, or it can also be taken at the Utility meter. I did both to cross verify them.
I have done this at a few stages during the day, and especially at mid-day when the production is at its peak, and I am finding somewhat lower numbers that the one advertised, so I am curious if other people have done this and what they found.
My Inverter is rated Peak/CEC Weighted (PV to Grid) of 96%/95.5%, but using the method above, I am measuring just below 93%.
Does that seem reasonable and explainable by other losses in the circuit or do you get better matching of spec efficiency vs real efficiency?
Thank you for sharing
What I mean by efficiency is AC power coming out of the inverter divided by the DC power going into the inverter.
Here are the measuring method I used.
DC in:
I have separate panel monitoring (optimizers), so I can get the DC in in two places, directly at the array with the optimizers reporting, and from the Inverter solar production. I have already found the Inverter number to be on average 0.9% below the array, which I assume are the line losses.
Note: If the only report of the solar production comes from the inverter one would need to be sure of where they measure it.
AC out:
For the AC coming out, I figured the best way to be sure of that is to turn off ALL the house breakers, leaving just the Inverter breaker on, and measure the Grid Export. That should give me the actual AC power the inverter creates from the Solar input. The grid export can be taken from the grid monitoring reading if its accuracy has been verified, or it can also be taken at the Utility meter. I did both to cross verify them.
I have done this at a few stages during the day, and especially at mid-day when the production is at its peak, and I am finding somewhat lower numbers that the one advertised, so I am curious if other people have done this and what they found.
My Inverter is rated Peak/CEC Weighted (PV to Grid) of 96%/95.5%, but using the method above, I am measuring just below 93%.
Does that seem reasonable and explainable by other losses in the circuit or do you get better matching of spec efficiency vs real efficiency?
Thank you for sharing
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