Why am I not 100% self-powered? App doesn't take into account exports?

[Grayson73]

Yesterday, I generated 48.2 kWh, home used 21.1 kWh, grid imported 7.5 kWh and exported 34.6 kWh so I would think I would be 100% self powered. Why does it think I used 37% from the grid rather than 0%? It doesn't take into account exports?

 

[jjrandorin]

I have never tried to look closely into the formula or anything, but.... grid draw isnt self powered. I have always thought of that number as "how close are you to not using the grid at all". Not "how close are you to offsetting what you used from the grid".

If your solar + your powerwalls can cover your usage, and you dont draw anything from the grid, you get a high self powered number on that card.

 

[RKCRLR]

The percent self-powered is the amount you draw from your solar and Powerwalls vs the grid. Drawing from the grid will lower the percentage even if you put more into the grid than you take out. If you don't draw anything from the grid it will show 100% self-powered.

 

[ucmndd]

Self powered is not the same as net producer.

 

[Matt-FL]

I think something might not be setup properly. Mine is similar to yours in graphs, but it only shows 1% for grid. The 1% makes up for the occasional sync/spike draws.

 

[GregBallantyne]

I've noticed this as well. The upshot is that seeing see a reported 100% self powered day via the app is either non existent or very rare. The app can (and routinely does) show a 99% self powered day when the grid data shows 0.0 imported. It also consistently shows what you noticed, if you draw some grid and then exporting more still shows up as less than 100% self powered.
Perhaps there is a justification (as some suggest) for this in definition, but I consider it a flaw. Being a bit of a data hound, I keep my own spreadsheet that reports self powered percentages more accurately. I'm coming up on 10 months of operation, so it remains to be seen if I continue to keep daily data, but for now I'm keeping at it.

 

[Redhill_qik]

Yesterday, I generated 48.2 kWh, home used 21.1 kWh, grid imported 7.5 kWh and exported 34.6 kWh so I would think I would be 100% self powered. Why does it think I used 37% from the grid rather than 0%? It doesn't take into account exports?

Self-powered means that your house load is powered directly by your self-produced and self-stored power which is either your Solar or your Powerwall.

Exporting to the grid and then importing it in the middle of the night is not direct use of your self-produced or self-stored power. Think of this as a measurement of being to be able to power your home when the grid is down. If you want to increase your self-powered percentage then switch the Powerwall "Operational Mode" to "Self-Powered" and decrease the reserve level of your Powerwalls so that they are used more when solar isn't producing.

 

[lodar]

I think something might not be setup properly. Mine is similar to yours in graphs, but it only shows 1% for grid. The 1% makes up for the occasional sync/spike draws.

This goes back to my “balancing a broomstick on your hand” analogy. While connected to the grid, the CTs monitor energy flow in / out from the grid. The TEG sends commands to adjust the PWs output voltage to push just hard enough against the grid to maintain a zero current.

But it takes time to react to sudden changes, so a little current slips in / out when a load turns on or off.

All those slips add up over the day to 1%, spoiling your perfect stat.

The only way to ensure a perfect self powered day is to disconnect from the grid. Physically by flipping breakers or virtually through the app.