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USA solar production - wattage mismatch

I’m in the US, with a 3.68kW solar array. This hits an inverter, then feeds into my panel using a 2-pole 20-amp breaker. I have a 20-amp CT sensor on each leg of this circuit (black and red wires) feeding into an emonTX (ports 3 & 4). I have updated the scale factor in emonhub to 0.267 as referenced on the shop page for the 20-amp sensor.

When I look at the inverter, it’s currently showing 90 watts for the power out. EmonCMS sees about 50 watts (the 2 inputs are currently 26 & 25). Vrms on the EmonTX is currently 114, and the DIP switch is set for USA.

I also have 2x 200-amp CT sensors on my main feeds from the utility, feeding into ports 1 & 2 on the emonTX. The wattage there is correct within a couple percent.

Any thoughts why would I see this mismatch?

Aside from possible engineering tolerances ganging up in one direction rather than averaging out by luck, another possibility could be the inverter is producing x, consuming y to run and that leaves z coming out for the emontx to detect. The reason I used x,y and z is because I’m not suggesting the emontx and/or inverter are spot on therefore the inverter must be consuming 39W, rather that what ever it might be consuming may bring the numbers closer together, there will almost always be differences.

That number sounds a bit low. If you’ve got access to a reasonably accurate voltmeter,
you should measure your mains voltage. If it is low, there may be other issues present.
If it measures 120 to 125 Volts, as I’m thinking it will, (I’m in the US too) that sounds like your
emonTx needs to be calibrated.

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Mains voltage is 125 on the voltmeter, which jives with the inverter - it shows grid voltage at 250. I’ve also got an emonPi in the garage that shows nearly the exact same Vrms as the emonTX - is it to be expected that they’re both out of calibration identically? I’ll work on getting them calibrated, but the similarity in Vrms threw me off

The inverter does show power in and power out, and there is a difference of ~50 watts, which I’m assuming is the inverter’s load. But I’m thinking the power out from the inverter should be what it’s actually sending to the grid.

Not expected, and though the odds of it are pretty tall, not unheard of.

From memory, the voltage tolerance on the USA a.c. adapter alone is ± 5%, so it does look as if the tolerances have all gone the same way.