Solar production/consumption correction factor

voltage-discrepancy

#1

Just wanted to start out by thanking everyone at Sense for chasing down some of my bugs, and implementing the voltage reading fix a few weeks ago. Since getting caught back up, I was able to collect some readings over the past week to compare Sense numbers to those on my two meters.

Just going off of the daily summed data from Sense, over the past week my solar production came in at 154kwh, while my consumption came in at 183kwh. According to my meters, my solar production was 158kWh and my consumption was 189kwh. The error, for both, comes out at ~3%, which is approaching margin of error I think. It’s also good that the magnitude and direction are the same, i.e. it’s not like Sense is telling me I’m producing less than I’m actually producing, and using more than I’m actually using.

When I tediously went through the daily raw data from Sense, things weren’t much different: solar production at 153.6 and consumption at 183.1.

Soooo…where do we go from here? Howard mentioned this a while back, and as he was correct on the voltage issue I think he’s correct when he brought up having a correction factor that each individual user could enter to correct their raw data. In my case, I’d want to add 3% to both my solar production readings and consumption to better equate with what our electrical company is charging us. Hard to say who’s “righter” in this case, but in the end the power company is who’s in charge of billing :slight_smile:

For that reason, my one request on the product wishlist is to be able to enter a correction factor for our hourly/daily data readings to be better in line with what our meters are telling us (presumably not everyone will be -3%). This will be important if we ever get some of the other things on the wishlist like being able to calculate costs and savings on a daily or monthly basis.

I’ll be content with the appliance discovery as it stands :slight_smile:


#2

Does your solar system show a negative value after the sun in down? Mine does. Its about 8-12 watts.


#3

Mine tends to show 1W all night long.


#4

Mine shows positive 2 watts at night.


#5

Do you have battery backup?


#6

Mine does as well: (-)1-4w typically. I can only assume this is a trickle charge to the inverter or simple baseline fluctuations. No battery backup.

For any users paying attention, I may have an update to this thread in a day or two.


#7

No battery backup. It is funny as while the sun is going down it will sometimes go as far down as -8 watts, but once there is no sun it stays stable at 2 watts. Perhaps just noise or a slight calibration error, no big deal.


#8

Mine also shows 4 watts at night. I’m pretty certain the moon and stars can’t quite accomplish that :slight_smile:


#9

Just wanted to provide an update on this, and I think that the Sense engineers will be on top of it soon. It’s my belief that the voltage fix that was rolled out wasn’t completely applied to the solar CT side of the equation. I spent the past few days taking pre-sunrise and post-sunrise readings of my two meters. The discrepancy that I see was most profound during the day - at night my Sense usage values and my energy meter matched very closely; during the day, my Sense solar was off by 3-4% and my usage was also off by 10-20% that I think could be directly attributable to the solar misreadings since much of my usage during the day was coming from solar.

Edit: the solar discrepancy accounts for the corresponding discrepancy in usage exactly.

Spreadsheet attached to show my work :slight_smile: