# Help in understanding web app Solar tab definitions

I have a Sense with Solar option installed.
I am examining the Solar Tab on the web app and looking for more detail in the report labels.
in this post I am examine one billing period where my utility co measured my net usage at 264kWh.
Sense measures grid power at 50% of real value. (see my post in wishlist category)
Sense measure solar power generated at 100% actual.
hopefully a snapshot of the wep app “solar tab” for one billing period is displayed below.

can someone expand on the definitions used:
Production? [474,3kWh] is this solar production?
Usage? [438.8kWh] is this total power used by the house ? times 2.0 in my case.
Self Powered? [100%] no idea what this means
To Grid: [320kWh] my PV system independently reports 484kWh generated for month. what could this be?
From Grid: [285.4kWh] can someone explain this? actual net utility billed 264kWh (see above)
Powered by Solar: [35%] confusing definition - also the 2x power measurement confuses more.
Net Solar: [35.5kWh (108%) probably confused by the 50% incoming power measurement.

anything will help make this more useful - as i’m currently in the dark (so to speak)

From Sense Help - I have amended the two that I don’t think are documented. Sense is seeing 474.3kWh Production (100%) vs. 484kWh from your PV system. PV systems tend to show 2-3% higher than Sense, but Sense is actually more accurate when it comes to matching your utility meter.

But you make a mistake when you assume Usage is 2x the measurement. In most cases the Sense CT do not measure your house usage, but rather your net usage, and in your case 1/2 the net usage. When Sense computes your Usage, it adds the Solar (you at 100%) to the measured net at the mains (but you are only adding 50%). Your Solar Production will be correct for the month, but you’re going to need to unravel the algebra / calculus to get to your true Usage.

Production
Your total solar production for the period selected. The given cost is based on your billing rate, if provided.

Usage
Your total, whole-home consumption for the period selected. The given cost is based on your billing rate, if provided.

Self powered
Percentage of your Solar Production / Total Usage. Can’t be more that 100%.

To Grid
Your excess solar production sent to the grid. The given cost is calculated based on your sellback rate. You can set this in the Solar Settings screen.

From Grid
Your usage pulled from the grid and not covered by solar. The given cost is based on your billing rate, if provided.

Net solar
Production minus Usage. This should be very close to To grid minus From grid.

i must assume then that “Usage” is not a strict reflection of power consumed/measured at the main breaker supplying the “whole home”. in other words, the Sense makes a calculation of Usage that involves measurements made at both the solar and the non-solar CT clamps.

Typically the word “Usage” has an unambiguous connotation but not in this case.

my PV installation and integration with the utility grid as a simple one. I have the fortunate situation where the grid is a perfectly efficient “battery”. energy consumed increments the meter, energy generated (PV) decrements the meter. my billing reflects the delta between the beginning number and ending number of a billing period. that number (kWh) is a either a positive number or a negative number. at the end of any 12 month period it is always a positive number (unless i get rid of two BEVs)

Maybe I didn’t explain correctly - your hookup of Sense is the issue. In most homes with Solar, the Sense CTs on the mains are measuring Net Usage, because they are located at the interface between the house and the grid. Sense computes the Total Usage for the house by adding the Solar feed-in to the measures Net Usage at the mains. Since you are only measuring one of the two buses for each leg of the mains your Sense is only seeing half the Net Usage. The problem is that is not the same as half the Usage. You can work backward from Sense’s numbers by doubling your Net Production from 35.5 to what it actually is (71).

I would be interested in how your utility comes up with their Net, because those numbers don’t seem to agree.

the number i quoted from my utility bill, 264kWh, is calculated by subtracting the number of kWh indicated on the meter on day 0 of the billing period from the number of kWh indicated on the meter on the last day of the billing period. ( here i may not be using the word “net” correctly altho…)

continued … even though the delta is 264kWh that meter arithmetic will result in a negative number for most of the summer months.