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How do I charge my Model Y using only excess solar power?

I have a 5x Powerwall-2 whole house backup with a 14.2kW PV solar panel system. I would like to charge my Model Y using only excess solar power, independent of peak or non-peak utility rates. The reason is to reduce the newly imposed "cost of transmission" charged for any power I draw from the grid. As a net producer of power, I am compensated only at the wholesale price of power, so I don't use my batteries to self-power during peak times.
I don't see the option on my Tesla app to charge only when I am exporting power to the grid. (I can limit the amount of power the Model Y uses for charging. I also limit the start and stop time for charging to correspond to peak solar production. However these settings change with the seasons, so automation seems preferable.)
Any suggestions appreciated.
 
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power.saver

Grid Specialist
Supporting Member
Mar 4, 2018
699
748
Arcadia, CA
I have a 5x Powerwall-2 whole house backup with a 14.2kW PV solar panel system. I would like to charge my Model Y using only excess solar power, independent of peak or non-peak utility rates. The reason is to reduce the newly imposed "cost of transmission" charged for any power I draw from the grid. As a net producer of power, I am compensated only at the wholesale price of power, so I don't use my batteries to self-power during peak times.
I don't see the option on my Tesla app to charge only when I am exporting power to the grid. (I can limit the amount of power the Model Y uses for charging. I also limit the start and stop time for charging to correspond to peak solar production. However these settings change with the seasons, so automation seems preferable.)
Any suggestions appreciated.
The Tesla app doesn't support this. However, see this thread for a way to do it.

 
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h2ofun

Active Member
Aug 11, 2020
3,702
893
auburn, ca
I have a 5x Powerwall-2 whole house backup with a 14.2kW PV solar panel system. I would like to charge my Model Y using only excess solar power, independent of peak or non-peak utility rates. The reason is to reduce the newly imposed "cost of transmission" charged for any power I draw from the grid. As a net producer of power, I am compensated only at the wholesale price of power, so I don't use my batteries to self-power during peak times.
I don't see the option on my Tesla app to charge only when I am exporting power to the grid. (I can limit the amount of power the Model Y uses for charging. I also limit the start and stop time for charging to correspond to peak solar production. However these settings change with the seasons, so automation seems preferable.)
Any suggestions appreciated.
For my solaredge inverters, I could buy the kit that allows me to charge en EV from them. Would this not work since it I believe would be solar only?
 
Holy carp that's a big system. Anyways have you set the car to charge during the period in question?
The only way I can do this is a combination of limiting the rate of charge to 7.5 kW and starting charging at 10:30 am. Based on the other information on this thread, it looks like Tesla would have to provide this option if enough people request it.
PS - The system size was based on an engineering analysis. Interestingly, using PowerWalls was significantly less expensive (and more reliable) than a 25kW generator.
 
The Tesla app doesn't support this. However, see this thread for a way to do it.

Thank you for your reply. I will look at this.
 
.... The reason is to reduce the newly imposed "cost of transmission" charged for any power I draw from the grid. As a net producer of power, I am compensated only at the wholesale price of power, so I don't use my batteries to self-power during peak times.
....
Interesting. How much is that charge? Is it tiered? Actually charged at each billing cycle or just a bookkeeping issue and offset at true up?
Is it an annual true up or monthly?
Before my area went to the Central coast Community generating, PG&E only paid the wholesale as well or below but now at least it is almost 7 cents/kWh.
I thought Santa Barbara joined our CCC.
 

h2ofun

Active Member
Aug 11, 2020
3,702
893
auburn, ca
The only way I can do this is a combination of limiting the rate of charge to 7.5 kW and starting charging at 10:30 am. Based on the other information on this thread, it looks like Tesla would have to provide this option if enough people request it.
PS - The system size was based on an engineering analysis. Interestingly, using PowerWalls was significantly less expensive (and more reliable) than a 25kW generator.
Less expensive? My generator 22kw was like 15kw, and can be used all the time, night and day
 

miimura

Well-Known Member
Aug 21, 2013
7,319
7,304
Los Altos, CA
It is possible to use the Master / Slave power sharing function on the Gen2 Wall Connector to modulate the pilot signal. If you have a way to measure the net power flow at your meter, you can signal the Wall Connector to only deliver surplus solar. See this thread:

 
I live off-grid and charge my car at home. I have batteries that run at 24v dc. The PV 24v dc charges the batteries. Inverter/charger, 24v dc/120v ac, is connected to batteries along with PV array. Inverter/charger is connected to house. Plug tesla provided charger into outside 120 volt plug from inverter/charger and tesla. Am looking into a 48v dc system. I am in process of getting another inverter/charger which will allow 240v ac or dedicate one to charging tesla.
would be nice to have a 24v dc charger that changes to the required dc voltage needed to charge tesla. It would have no impact on my inverter/charger I use for the house.
 
You are going to find more choices in a 48 volt battery/inverter environment. Also those inverters will have more functionality that you might find useful in trying to charge an EV. The most efficient process would be to charge from solar and let the inverter balance the available solar with a little from the batteries if a cloud passes by.
 
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