Has anyone else compared the Electric company’s data to CT data you acquire through a device like Neurio or Sense? I have a neurio and my comparison shows that from the time my PV system begins to produce until about 10 PM the usage values from the electric company is twice that shown by my Neurio.
Note that the production data tracks nearly dead on but the Consumption only tracks closely before 6am and after 10pm. Am I being ripped off by the electric company?
I don’t think you’re being ripped off. Utility meters are significantly more accurate than devices that use clamp on ammeters like Neurio or Sense. That said, Your graph has some issues that make me question what you are really looking at. For Production, Net and House use, you indicate units of kWh (energy), but the shape of all of the traces look like instantaneous power (kW). It’s not uncommon to see differences between two different devices when looking at instantaneous power as your seeing discrete points in time. Each device is taking a measurement at a slightly different time and your instantaneous usage varies from moment to moment. It may also be that one device is reporting average power over a given period while the other is reporting max or just the actual at that moment.
To sum up, instantaneous power is nice to look at, but your charges and savings come from total energy used or generated so if you can compare those, that would be more beneficial. If you’re interested, you can look at my system here: Schaffer to see what the shapes of these curves should be for Power and Energy. My system is in Orange County California in SCE territory. I’ve been keeping track of my usage for about 6 years using a TED System and than comparing to my meter readings. I’ve not noticed any significant difference between SCE and my readings except when there was a problem on my end.
Resolved the problem with the Neurio to Electric Co., comparison. I found that due to my placement of the Neurio sensors I had inadvertently connected both to the same phase causing the difference. With the help of a Neurio technician that my main breaker was one of the few which switched the phases from the input to output sides.
As you can see it looks like I have them connected to both phases but the internal switching of phases caused both to be on the same phase. I did it this way because the L1 incoming lead was too short to connect it at the top so I assumed the bus bar was directly below the lug resulting in the incorrect installation. I have corrected it by moving the CT to the right hand bus bar and the results can be seen here showing a much closer match in data:
Since these data are for five minute intervals differences of 1% are not uncommon but acceptable.
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That’s really interesting. I’ve been an electrical engineer for 30 years and I’ve never heard of a breaker that transposes the poles internally although most of my experience has been with much larger frame breakers. I don’t know if I would have thought of that as a possible issue. Not that you need to change anything now, but could you have installed both CTs on the load side of the breaker? I would guess not from the photo.
I have a bit of an issue with the CTs on my TED system as well. The main breaker in my panel is actually two 2-pole breakers connected in parallel. There are two wires per pole coming from the meter side of the panel and the breakers are connected directly to the load bus without any wire. I have two CTs around one of the two Line leads for each pole and have to apply a multiplying factor in the TED software to multiply the readings by 2. It’s not ideal, but it’s been pretty accurate over the years. I’ve considered breaking the seal on the metering side of the panel and installing the CTs around the utilities leads but just never got around to it. The utility does all their meter reading remotely via the smart meter so there’s very little chance they would ever be around to see the broken seal.
It shouldn’t matter where you install the CTs since the same current is flowing in those conductors. It sounds like your electrician didn’t have the correct gage wire it he used two conductors. I would think that putting the CT around both wires would solve your problem since the combine currents would be detected by the CTs unless they would not fit into the opening in the CT. That would avoid the need for a 2x multiplier.
Since PVOutput doesn’t make it easy to upload data from the Neurio I have had my grandson code an api to do that. It’s running now and we are trying to debug it to keep it from hanging at various times throughout the day. I assume you have to do similarly with the TED.
No mistakes by the electrician, that’s the way the panel manufacturer designed the panel. The Main Breakers and the wiring from the meter section are pre-assembled and fixed.
You’re right that putting the CT around both wires of a given pole would be more accurate, but the physical arrangement of the panel makes this impossible.
As far as getting the data from the TED to PVOutput, I did write my own script that queries the TED every 5 minutes and then uploads to PVOutput via its API. I don’t worry too much about the overall accuracy as I also use an Eagle Gateway to query my smart meter and upload my Net energy each day. I usually track within a couple of percent of the TED so I’m happy.