Difference between inverter kWh output # and meter output #?

Is this pretty typical or something that needs to be looked into?
Now that I have an actual meter from the POCO, I can check it against my inverter and again the TED5000 (which has always shows a little less than the inverter). Well, the meter itself actually shows lower than the inverter as well.
SolarEdge Inverter: 53.38kWh
POCO Meter: 51kWh
TED5000: 51.5kWh
I thought maybe the inverter is showing DC kWh and not AC, but they are too close, if that was the case the difference between them would be bigger.
Now that I have an actual meter from the POCO, I can check it against my inverter and again the TED5000 (which has always shows a little less than the inverter). Well, the meter itself actually shows lower than the inverter as well.
SolarEdge Inverter: 53.38kWh
POCO Meter: 51kWh
TED5000: 51.5kWh
I thought maybe the inverter is showing DC kWh and not AC, but they are too close, if that was the case the difference between them would be bigger.
Comments
Here is an interesting white paper on Utility meter accuracy:
http://www.cpsenergy.com/files/Smart_Grid/smart_meters_epri1.pdf
-Bill
Basically my concern is...is there something going on that could be fixed so that 53kWh that the inverter shows makes it to the meter? Or the invert is just inaccuarte?
For example, if you have 240 VAC at the meter and 250 VAC at the inverter output--That would give you a ~4% line/power loss.
-Bill
I can take a multimeter to it later and check actual voltages, but that's what I was able to gather quickly.
Each meter can be easily be off by 0.6% -- So, 1.1% difference is not impossible to explain by meter accuracy.
-Bill
47.5 amps * 6 AWG * 15 feet @ 240 VAC
Voltage drop: 0.56
Voltage drop percentage: 0.23%
Voltage at the end: 239.44
-Bill