Who is more precise / accurate

Technical Questions
1

I have solaredge app the tracks energy use and solar production. There is about 3kWh difference between what solaredge reports and what sense reports. Which app is more precise? See attached
.

Screenshot_20200502-180034_Sense
Screenshot_20200502-180034_Sense1440Ă—3040 344 KB
Screenshot_20200502-180042_SolarEdge
Screenshot_20200502-180042_SolarEdge1440Ă—3040 509 KB

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2

Is the solaredge app hooked up to the inverters? If so, most definitely that vs CT clamps on a wire. Being told something has to be most precise than measuring it.

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3

That’s a good question. The answer in my mind is “it depends”. It depends on two things:

  1. Precision vs. accuracy - I’m assuming you mean accurate vs precise. Precision has to do with the number of decimal places in the measurement and how repeatable the same measurement is. Accuracy is about how close the measurement is to the “real value”.
  2. What is the real value ? The inverter and the Sense CTs are measuring two slightly different things. The inverter is measuring the power coming out of some stage within the inverter, hopefully close to output. Sense is measuring the feed-in power to your panel. There are probably a couple of power losses that happen between those two points. The thing that I have found is that Sense solar is more accurate / consistent if you want to compare Sense net power vs. your utility company bill. My SolarEdge inverter was consistently 4% higher than my Sense solar, but the Sense Total Consumption - Sense Solar was consistently much closer to my net meter output. Here’s the analysis:
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4

By itself the solaredge inverted only counts the power generated by the solar panels (green graph on the image.) To calculate power coming in from the grid (red) and self consumption (blue), requires connecting a modebus meter which also uses CT clamps. The clamps placed on the two phases coming from the main meter.

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5

Seems like you are pretty well instrumented to compare Sense results vs. SolarEdge + modebus, vs. your utility meter. I have found that for basic comparison it is simpler to export daily Sense data and compare. If you can do the same daily export for SolarEdge + modebus and your net-usage from your utility, the 3-way comparison would be interesting.

6

I too was seeing about a 4% on average difference between what Sense reports and what my APS micro-inverters were reporting (with Sense being the lower number). My theory is, the inverters were reporting DC power, where as Sense is reporting AC power. The 4% difference is accounting for DC-AC conversion loss.

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7

Here is my April numbers from Sense and my inverters. Pretty close.

Enphase Production 1505.052
Enphase Consumption 1149.010

Sense Production 1503.571
Sense Consumption 1145.586

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8

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