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Home Energy Use Discrepancy Emporia vs

My home usage is consistently different between Emporia vue on my circuit breaker panel vs what tesla reports. Average Emporia use is about 70 kWh per day and from tesla is about 80 kWh. Utility seems to more closely match tesla, but it's hard to tell because of net metering.

On an instantaneous basis, it's common for emporia to show 2kW of power use mid day, and tesla to show 3kW at the same time. That's mid day baseline without ac running and with high solar production.

Our solar system is 18kW with 12.6kW of inverters and two powerwalls.

Are the inverters or some other solar component somehow using 1kW mid day? Could difference be because of voltage irregularity from the mains? Like maybe actual mains voltage is 250V while solar is producing but Emporia assumes 220, so there's higher wattage than Emporia can see?

Any ideas? Mostly I want to discover if there's actually 1 kW of phantom power usage somehow.
 
In my OPINION the Emporia Vue is more accurate than Tesla app when the sun is shining and Solar is charging the powerwall, but when just the power wall or grid powering the house, (NIGHT TIME)Tesla and emporia measurement are almost identical, I think the Tesla app showings more when solar is charging the powerwall and providing power to the house because it compensates the 90% round trip to charged and discharged the powerwall.
 

BGbreeder

Active Member
Jun 19, 2020
1,113
791
Bay Area
  1. Turn off your solar.
  2. Note the meter reading
  3. Wait an hour
  4. Note the meter reading
  5. Compare the two apps to the difference in the meter reading
The only certified measuring device is your meter. Obviously, once you have to two apps sorted out, you can add solar and see how well that matches with the corrected consumption of the house and the meter.

My global comment is that neither of the apps is likely to be on the money.

All the best,

BG
 

miimura

Well-Known Member
Aug 21, 2013
7,397
7,400
Los Altos, CA
I am not familiar with the technical details of the Emporia system. If it can't see the voltage of each phase in real time, it cannot be accurate on power. I know the Tesla Powerwall hardware (Gateway or Backup Switch) can read the instantaneous voltages, so its power calculation should be accurate if the CT current readings are accurate. However, people have reported that their CTs were bad and got terribly inaccurate readings until the CTs were replaced. This is a recent issue that I didn't hear about before Generac acquired Neurio.
 
I am not familiar with the technical details of the Emporia system. If it can't see the voltage of each phase in real time, it cannot be accurate on power.
From the Emporia Vue installation manual: "The wire harness allows for single-phase power and three-phase voltage sensing: White connects to Neutral, Black provides power and voltage sensing, and Blue and Red enable voltage sensing only." So at least for typical USA split phase wiring, the Vue system can measure power accurately. However, the current sensing will work even if the voltage sensing leads aren't connected, and the manual shows how to wire it without voltage sensing if there are no unused breakers in the panel, and the installer doesn't want to shut off the main breaker. So some users may install it without voltage sensing and so have poor accuracy. [We have a full panel, but I could still connect the voltage sensing, and of course shut off the power while making the connection.]
 

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