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Powerwall2/Gateway 2 Metering

megooden

New Member
Oct 7, 2021
3
1
Rio Rancho, NM
I am having two Powerwalls and gateway 2 installed. I have been going over the installation manual to understand how everything works and make sure my installers do it right (I am their first install). Everything will be wired for whole-home backup with the Powerwalls and solar coming into the gateway 2, as well as the grid directly from the meter.

The gateway 2 comes with 1 CT (current transformer) and as far as I can tell it is supposed to be used to monitor the solar production. The Powerwalls monitor themselves and the grid is monitored already in the gateway. I am confused though on how the usage for the house is determined? The app is supposed to show usage for grid/solar/PW/home but only 3 of the four is monitored. Do I need another CT to monitor the house usage?

Thanks,
 

GenSao

Member
Aug 3, 2017
581
1,013
Pleasant Hill, CA
The gateway 2 comes with 1 CT (current transformer) and as far as I can tell it is supposed to be used to monitor the solar production. The Powerwalls monitor themselves and the grid is monitored already in the gateway. I am confused though on how the usage for the house is determined? The app is supposed to show usage for grid/solar/PW/home but only 3 of the four is monitored. Do I need another CT to monitor the house usage?

Megooden,

Welcome to the Tesla Motors Club. Enjoy your stay.

A separate CT is not required. Home usage will be calculated from the difference between 1) grid use, 2) solar production, and 3) battery use. When the grid is down, home use can be calculated from solar production and battery use.
 

megooden

New Member
Oct 7, 2021
3
1
Rio Rancho, NM
Megooden,

Welcome to the Tesla Motors Club. Enjoy your stay.

A separate CT is not required. Home usage will be calculated from the difference between 1) grid use, 2) solar production, and 3) battery use. When the grid is down, home use can be calculated from solar production and battery use.
Thanks! That is what I figured but since I couldn't find anything that explicitly said that I wanted to make sure. My installer wanted to place the CT that came with the gateway 2 on the lines going to my panel to monitor the house usage and I didn't think that was correct.
 

GenSao

Member
Aug 3, 2017
581
1,013
Pleasant Hill, CA
Thanks! That is what I figured but since I couldn't find anything that explicitly said that I wanted to make sure. My installer wanted to place the CT that came with the gateway 2 on the lines going to my panel to monitor the house usage and I didn't think that was correct.
No worries.

Do note, the CT that monitors grid use can be placed in the gateway or closely behind the meter. If you have non-backed up loads, I recommend having the CT monitor grid power closely behind the meter. If placed here, the Powerwalls (while the grid is active) can measure total home loads (not just in the back up panel) and offset power costs during peak time of use (TOU) rates.
 

megooden

New Member
Oct 7, 2021
3
1
Rio Rancho, NM
Thanks for the information, helps understand how things do/can work with the system. I won't have any non-backed up loads though. I will have the one CT that came with the gateway monitoring the solar and the grid will use the built in CT that will monitor the grid power which comes directly from the meter into the gateway. If we add anything later I may need to add an additional CT to monitor things. Appreciate the quick response as well! Powerwalls and gateway just went up on the wall this morning, excited to see them working.
 
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