To Powerwall + Home usage - grid usage higher than solar output?

[morph3ous]

I noticed today that the numbers I am getting for power usage/production are not adding up. In this example, my home has used 93.3 kWh. I sent 37.5 kWh to the PowerWalls. So that is a total of 130.8 kWh of consumption. I drew 1 kWh from the grid. That means I should have generated 129.8 kWh from my solar panels. It is reporting 104 kWh from solar. I wonder where the extra 25.8 kWh came from.

Has anyone else seen this?

 

[dareed1]

Your consumption is the Home Usage + To Powerwall + To Grid = 93.3 +37.5 + To Grid = 129.4kWh + Unknown amount exported to Grid
The supply was Solar + From Powerwall + From Grid = 104 + 36.1 + 1 = 141.1kWh.
Presumably the amount you sent to the grid was 11.7kWh approximately.

 

[morph3ous]

You’re right. That is about what it is saying. I was looking at it all wrong. Thanks @dareed1.

 

[Kappytime]

Your consumption is the Home Usage + To Powerwall + To Grid = 93.3 +37.5 + To Grid = 129.4kWh + Unknown amount exported to Grid
The supply was Solar + From Powerwall + From Grid = 104 + 36.1 + 1 = 141.1kWh.
Presumably the amount you sent to the grid was 11.7kWh approximately.

I would love to hear your thoughts on a twist to this thought exercise.
I am running a completely off-grid 10kW solar system in Central America with two PowerWalls and a back-up generator.

Using the formula:
Consumption is the Home Usage + To Powerwall + To Grid = 20.5kWh +18.9kWh + To Grid = 39.4kWh + Unknown amount exported to Grid

Supply is Solar + From Powerwall + From Grid = 13.2 + 19.3 = 32.5kWh.

My supply is LESS than my consumption - it doesn't seem this should be possible.

 

[Southpasfan]

I would love to hear your thoughts on a twist to this thought exercise.
I am running a completely off-grid 10kW solar system in Central America with two PowerWalls and a back-up generator.

Using the formula:
Consumption is the Home Usage + To Powerwall + To Grid = 20.5kWh +18.9kWh + To Grid = 39.4kWh + Unknown amount exported to Grid

Supply is Solar + From Powerwall + From Grid = 13.2 + 19.3 = 32.5kWh.

My supply is LESS than my consumption - it doesn't seem this should be possible.

These are always fun. But I also don't see how "to Powerwall" can exceed "from Solar" especially when you are off grid.

It could happen in the US during "Stormwatch" mode where the powerwalls are charging from the grid, but not in your situation.

Also, the graphic looks like most of the solar went to charge the powerwalls.

One clue might be that for a 10kwh system 13kwh is really low for a whole day in June, even with clouds. But it looks like you had rain in the afternoon.

 

[dareed1]

I think we need to establish if the plotted data is fully self consistent. It is hard to tell from the screen shot, but it appears to me that when solar production is more than a couple of kW, the reported house usage is zero. Would you mind getting separate screen shots for each of solar, house usage, and battery? I'd like to rule out the possibility of incorrect installation of the current transformers.
Also, is the cause of the sharp drop outs of solar production in the afternoon caused by the PWs being fully charged?

 

[getakey]

were the dips in solar caused by clouds?
If not, I would say CTs are not installed correctly

Also, how do you have more power going into PW than produced by solar?

 

[getakey]

formula should be
Solar - To PW + From PW - ToGrid + FromGrid = Home usage

 

[Kappytime]

Supplementing my earlier post, our system has 40 rooftop panels with a capacity of around ten kilowatts per hour, or 10kWh.

As requested, here are screenshots of each separate element. I am also attaching the downloaded data beginning at 10AM.

 

[getakey]

Supplementing my earlier post, our system has 40 rooftop panels with a capacity of around ten kilowatts per hour, or 10kWh.

As requested, here are screenshots of each separate element. I am also attaching the downloaded data beginning at 10AM.

I think your CTs are not installed correctly

 

[dareed1]

Yes, those screen shots show that the measured power going to the house is zero during period of solar production that is higher than a couple of kW. Presumably the house actually is consuming electricity in the middle of the day, so as getakey says, the most likely cause is an incorrect installation of the current transformers. That causes a measurement error but is unlikely to affect the actual operation of the system.