PowerWall Grid Charge limit

[ACarneiro]

Hello everyone.

I am thinking of installing a 8kWp solar array and two PWs with the gateway.
Currently at home I also have two EVs and two Tesla Wall Connectors and cheaper electricity for 7 hours during the night time.
Both EVs will charge during the cheap rate at 32A each (240V). My maximum current is limited by a 100A fuse outside the house.

In the UK during the winter I am unlikely to produce nearly enough solar to fill the PWs so my understanding is that it has the possibility to "fill itself" during the night at cheap electricity and then run the house throughout the day on a mix of solar (whatever little gets produced) and stored energy.

My concern is that when both EVs and the PW are charging, I will have a draw of 96A (32 for each EV and another 32 for both PWs).

QUESTIONS:

• When the PWs are charging, is the baseload from the house adding to the draw from the PW or is it all going through the PW anyway?
• Is there a way to tell the PW to limit the grid usage to no more than, say, 96A?

 

[gpez]

Hello everyone.

I am thinking of installing a 8kWp solar array and two PWs with the gateway.
Currently at home I also have two EVs and two Tesla Wall Connectors and cheaper electricity for 7 hours during the night time.
Both EVs will charge during the cheap rate at 32A each (240V). My maximum current is limited by a 100A fuse outside the house.

In the UK during the winter I am unlikely to produce nearly enough solar to fill the PWs so my understanding is that it has the possibility to "fill itself" during the night at cheap electricity and then run the house throughout the day on a mix of solar (whatever little gets produced) and stored energy.

My concern is that when both EVs and the PW are charging, I will have a draw of 96A (32 for each EV and another 32 for both PWs).

QUESTIONS:

• When the PWs are charging, is the baseload from the house adding to the draw from the PW or is it all going through the PW anyway?
• Is there a way to tell the PW to limit the grid usage to no more than, say, 96A?

I'm not familiar with how UK mains are configured - is the 100A fuse something that is part of your breaker panel or is it upstream from you? If it's part of your breaker panel it'd likely have to be upgraded as part of your install, if it's upstream or you can't change it you may be out of luck.

When the PWs are charging, is the baseload from the house adding to the draw from the PW or is it all going through the PW anyway? -> Adding to the house draw.

Is there a way to tell the PW to limit the grid usage to no more than, say, 96A? -> Not that I'm aware of.

 

[ACarneiro]

The 100A fuse is upstream from my board and “belongs” to the Distribution Network Operator (DNO).

Thank you for clarifying my questions. I’m going to have to have a thought about my options

 

[Nhallwood]

One option that you have is to set the times for peak and off-peak electricity. So if you know your EVs will be done charging by 3am you could set that as the start of off-peak electricity so the PW doesn't start charging till then. I've also noticed that when the PW is in the mode when it just stores solar and then uses it to cover additional load either during darker periods or overnight, it charges at a slower rate so draws less current. You can adjust the "minimum charge" level either with the app or using an API call which I do on a Raspberry Pi. It really depends on how much you want to just be able to "set it and forget it" vs. taking a more active approach. I'm in the latter mode but am hoping to learn from this (I've had the PW since Mid November) and then create some more automation. I'm in South West London in the UK so similar dynamics on electricity supply and solar generation.