Sense Solar Production reported wrong values on 1/23/2018-1/25/2018


#1

I was looking at my solar production numbers, comparing my SolarLog production meter (accuracy 0.2%) to my Sense solar production values.

Normally, unless power production is < 1.5 Kwh for the day, the Sense values are within a couple of percent from the actual value. But on certain dates, particularly 1/23/2018 through 1/25/2018, the Sense numbers were far off. Below is a chart of values. So the question was Sense updated during that time period or something else that created a Sense measurement problem.

|Date|SolarLog Meter Production Total Yield (Wh)|Solar Production from Sense Kwh|% diff Sense from solarlog meter info|
|1/1/2018|420|0.5|16.00%|
|1/2/2018|462|0.6|23.00%|
|1/3/2018|590|0.7|15.71%|
|1/4/2018|0|0.1|100.00%|
|1/5/2018|609|0.7|13.00%|
|1/6/2018|840|1|16.00%|
|1/7/2018|1045|1.2|12.92%|
|1/8/2018|1426|1.5|4.93%|
|1/9/2018|15614|15.7|0.55%|
|1/10/2018|21593|21.6|0.03%|
|1/11/2018|10868|10.9|0.29%|
|1/12/2018|11238|11.3|0.55%|
|1/13/2018|20634|20.6|-0.17%|
|1/14/2018|27167|27.2|0.12%|
|1/15/2018|4818|4.9|1.67%|
|1/16/2018|15204|15.2|-0.03%|
|1/17/2018|2554|2.6|1.77%|
|1/18/2018|18664|18.7|0.19%|
|1/19/2018|15486|15.5|0.09%|
|1/20/2018|15597|15.6|0.02%|
|1/21/2018|25945|25.9|-0.17%|
|1/22/2018|2036|2.1|3.05%|
|1/23/2018|902|2.9|68.90%|
|1/24/2018|24599|7.2|-241.65%|
|1/25/2018|33247|29.8|-11.57%|
|1/26/2018|33275|33.2|-0.23%|
|1/27/2018|28913|28.9|-0.04%|
|1/28/2018|10556|9.6|-9.96%|
|1/29/2018|12009|12|-0.08%|
|1/30/2018|694|0.8|13.25%|
|1/31/2018|19370|19.4|0.15%|

#2

I would first make sure your monitor didn’t go offline. I had a day in early January where I lost about 12 hours of reporting inexplicably. I’ll have to go back and check, but it may have coincided with the 1 year anniversary of installing my replacement unit. What was interesting is that it wasn’t the entire monitor for the entire 12hr period. The usage dropped for about 16hrs, and the solar dropped for about 9hrs?, and they only overlapped in the middle.

EDIT - looks like my new unit install was on January 4th, 2017, and the drop happened from Jan 2- Jan 3, 2018. Coincidence?


#3

During those times, I didn’t have a power failure, internet issue or missing data. But the data reported was not valid. I captured a screenshot on 1/24/2018 at 12:55am that shows 703 watts solar being generated (along with 705 watts being used).

I’m almost sure that there was no supernova on the dark side of earth illuminating my solar array (39 Sunpower 345w panels) at 12:55am! :grin:


#4

I had some problems with my CTs connection to Sense. I was getting really shaky readings for a while, which were most obvious at night because I could see my solar power fluctuating from noticeably negative to noticeably positive wattage. During the day, I could occasionally see blips in solar (and usage), but I wasn’t certain it wasn’t a freak cloud or something.

Sense advised that I disconnect the CTs and plug them back in. That worked for a week or two. I let it sit for a while before it started bugging me, and I went back out and used the Nintendo cartridge solution by blowing out the connections for the CTs. No problems since then.

Your issue sounds similar, but way more extreme. I don’t think my CTs ever read that far off.


#5

I haven’t had any problems with my CT’s being that far off since I had a proper installation about 1 year ago. And I checked the weather from my weather station on the roof, and the temperature was about 20 degrees F at that time, and nowhere near the subzero numbers we had the 1st week of January 2018.

And the CT’s never stopped operating, so it feels more like a software/firmware issue at Sense’s side.

I wonder if external utility line work can affect the Sense module (assuming no power loss)?


#6

Here’s my post from late last year on the subject, with some screencaps: