Discrepancies in my consumption data

Hi everyone!

So I’m happy to say that my system was issued PTO and turned on a little more than a week ago, and I just had a quick question regarding the data in Enphase Enlighten and how it compares to that of my utility.

When I look at the “imported from grid” data in Enlighten and compare it to the “consumption in excess of generation” from my utility’s smart meter, I get the following.

Date Enlighten (kWh) Utility (kWh) Δ%
2/18/2022 21.7 29.457 36%
2/19/2022 11.8 14.146 20%
2/20/2022 17.4 18.949 9%
2/21/2022 15.1 16.205 7%
2/22/2022 9.6 10.26 7%
2/23/2022 48.1 50.447 5%
2/24/2022 75.9 77.218 2%
2/25/2022 62.0 63.378 2%
2/26/2022 52.0 53.128 2%
2/27/2022 23.7 27.433 16%

I know the data won’t be a perfect match, as I believe the Enphase consumption CTs are +/- 2.5%, while obviously the utility meter is “revenue grade.” But the data can vary quite a bit, anywhere from 2% to 36%.

The consumption CTs are installed around the L1 and L2 wires emerging from the top of my main service panel, with the arrows pointing down towards the loads. No sub panels. And the consumption meter in Enphase ITK is set to loads only, because my PV is connected via a line-side tap above the CTs on the L1 and L2 wires on their way to the meter.

Does anyone have any thoughts? If the C1 and C2 CT meters were swapped to L2 and L1 in the service panel, would that explain it? Am I missing something else entirely? Or are these just normal variations?

If you’d like to see more data, I’m at The Solar Collective 11.250kW

Thanks for all your help!

Anyone have any thoughts?

Hi @tycho0. The DELTA between the two is substantial. I’m not familiar with Enphase specifically. I was wondering whether it’s possible that one of the CTs is either faulty or not properly connected to whatever they connect to. Is it possible for you to safely verify that both CTs are correctly installed and connected? Is it possible to interchange the CTs to see if that makes a difference?


Well, just wanted to follow up with everyone. I heard back from Enphase technical support, and they’re also thinking that one or both of the consumption CTs may be faulty. They suggest first replacing the CTs, and if that doesn’t fix the issue, then replacing the Envoy PCB next.
So now, time to reach out to my installer… Thanks for help, @grannos!