Another Powerwall + Solar + Grid question

[NYUES88]

Update some clarity, the third Tesla rep set they other two straight.

Tesla rep to us today:
I asked our energy expert to get clarification and I gave you the wrong information previously. Sorry about that.

For the Power wall with Solar, it won’t pull from the grid to charge unless under emergency situations. For example, extreme weather, natural disasters and/or power shutdown warnings.

The Power wall will use the Solar panels as its main source to charge the battery during the day ( most days, should charge the power wall fully) then use that stored energy at night while you are using electronics in the house. ( you can manage the Power wall via the app on how much energy you would use from the home and have power pulled from the grid).

Power wall without solar, will pull from the grid during off-peak hours to max out on savings and during the daytime the power wall will be the main source of power for the home ( Unless you control it from the app exactly how much power can be used, pending on the Utility provider).


Hopefully this clears the confusion up a little bit.

 

[Sonny85]

It is my understanding that if you are eligible for the SGIP rebate in California, (SGIP not eligible for PW and no solar) you can only charge from your solar and you must use at least 57 Kwh from your battery a month. (687 Kwh a year) Since Tesla is pretty much capped out on the SGIP rebates (unless installed by one of their authorized installers) you should have the freedom of charging from the grid even without storm watch. Tesla does not "control" storm watch. Storm watch is created by the utility company alerts. When the local utility company activates storm alert, Tesla receives this information and if your storm watch is active, your powerwall tops off with the grid and activates backup only mode until the storm alert is deactivated.

 

[jjrandorin]

It is my understanding that if you are eligible for the SGIP rebate in California, (SGIP not eligible for PW and no solar) you can only charge from your solar and you must use at least 57 Kwh from your battery a month. (687 Kwh a year) Since Tesla is pretty much capped out on the SGIP rebates (unless installed by one of their authorized installers) you should have the freedom of charging from the grid even without storm watch. Tesla does not "control" storm watch. Storm watch is created by the utility company alerts. When the local utility company activates storm alert, Tesla receives this information and if your storm watch is active, your powerwall tops off with the grid and activates backup only mode until the storm alert is deactivated.

Yes, tesla does control "storm watch".. because not every "weather alert" for your area will activate that mode. It is not from "utility company activating stormwatch" the alerts come from the national weather service, not from any specific utility.

 

[cwied]

It is my understanding that if you are eligible for the SGIP rebate in California, (SGIP not eligible for PW and no solar) you can only charge from your solar and you must use at least 57 Kwh from your battery a month..

The solar charging requirement is for the federal ITC, not for the SGIP. The SGIP just requires on full discharge per week and was available even for standalone battery installs (i.e., without solar). I ended up getting both the SGIP payment and the ITC for my install in 2018 since I do have solar.

I don't expect Tesla to support charging from the grid in the US until the ITC phases out.

 

[aesculus]

Yes, tesla does control "storm watch".. because not every "weather alert" for your area will activate that mode. It is not from "utility company activating stormwatch" the alerts come from the national weather service, not from any specific utility.

My understanding its sort of a three way thing between the utility, NWS and Tesla doing the notifications. But this is not based on any hard facts, just the typical TMC noise.

 

[cwied]

The one way the utilities are involved is when they call a public safety power shutoff for wildfire danger here in California. Tesla activated Stormwatch for those last year.

 

[jboy210]

The one way the utilities are involved is when they call a public safety power shutoff for wildfire danger here in California. Tesla activated Stormwatch for those last year.

Cool. I was thinking I would have to manage this by manually increasing the PW limits when the PSPS are forecasted for my area. But if the PG&W warning of these trigger Stormwatch I can let that handle the increase.

 

[aesculus]

Cool. I was thinking I would have to manage this by manually increasing the PW limits when the PSPS are forecasted for my area. But if the PG&W warning of these trigger Stormwatch I can let that handle the increase.

Just one word of caution. As soon as PG&E sets the notice for a PSPS in your area it can trigger a StormWatch event and your batteries will charge from the grid. All fine and dandy unless this happens during peak periods and your are paying max rate for power.

I leave mine on but turn it off once I see that it is working. Then wait until off peak to turn it back on again. Early on some people said if they turned it off it never went back on again but I did this a number of times and it worked OK for me. YMMV.

 

[SolarinSpokane]

I live in Spokane, Washington, and Avista is the power company. We are installing three PW, solar panels, and, to make it more complex, adding an EV that can do bidirectional charging. There is Net Metering on an annual basis.

When will the ITC phase out? It appears that (given the ITC and the U.S. government agreement with Tesla) in most cases (unless Stormwatch is triggered) the PWs do not draw from the grid.

I was wondering if a separate circuit for EV charging that bypasses the Tesla Gateway might be desirable so that the EV battery (165 Khw) does not drain the PWs completely without a means of recharging them other than the solar panels (a possible issue in winter). Perhaps there is no way to bypass the Gateway in this way. I am not confident that I will be able to charge the EV from the grid without going through the PWs. If I were to charge in reverse, vehicle to grid, charging to the PWs would be fine, but Net Metering makes direct connection with the grid seem desirable too.

 

[miimura]

I live in Spokane, Washington, and Avista is the power company. We are installing three PW, solar panels, and, to make it more complex, adding an EV that can do bidirectional charging. There is Net Metering on an annual basis.

When will the ITC phase out? It appears that (given the ITC and the U.S. government agreement with Tesla) in most cases (unless Stormwatch is triggered) the PWs do not draw from the grid.

I was wondering if a separate circuit for EV charging that bypasses the Tesla Gateway might be desirable so that the EV battery (165 Khw) does not drain the PWs completely without a means of recharging them other than the solar panels (a possible issue in winter). Perhaps there is no way to bypass the Gateway in this way. I am not confident that I will be able to charge the EV from the grid without going through the PWs. If I were to charge in reverse, vehicle to grid, charging to the PWs would be fine, but Net Metering makes direct connection with the grid seem desirable too.

If you want to charge the EV only from the grid, there are two different considerations:

1. The grid is up and you don't want the PWs to discharge into your EV. The most common way to do this is to use Time Based Control with an Off-Peak time defined when you want to charge the car. For people with Time Of Use rates, this is easy because you just set the PW configuration to match your rate schedule and set the car to charge during the cheapest times. If you don't have TOU rates, you could just fake it, defining an Off-Peak from say Midnight to 6am and set the car to charge during that window. If you want the batteries to power the house but not the car during that time, then it gets more complicated.

2. The grid is down and you don't want the PWs to discharge into your EV. As long as your EVSE circuit is outside the Tesla Backup Gateway, it will lose power when the grid goes down and it will be impossible for the car to discharge the batteries during a grid outage.

The complicated part:
If you want to run Self Powered and use the solar and batteries for everything EXCEPT EV charging, then you have to put your EVSE circuit(s) outside the Gateway and make sure that the Grid CTs are not measuring the usage of those circuits. If the EVSE circuits are the only things backed up, this is relatively easy because the default location of the Grid CTs are on the grid input of the Backup Gateway. So, the Powerwall system will basically be blind to that usage and it won't be measured at all by the Tesla system and the batteries won't be discharged to offset that consumption.

If you have the V2H bidirectional charger set up and want to use it to extend the runtime of your Powerwall batteries, you have to look very closely at how the system functions and whether it can be grid interactive or if it must be the only power source active on a micro-grid. If it is grid interactive, you have to figure out how it controls how much power is charged and discharged from the EV.

 

[SolarinSpokane]

If you want to charge the EV only from the grid, there are two different considerations:

1. The grid is up and you don't want the PWs to discharge into your EV. The most common way to do this is to use Time Based Control with an Off-Peak time defined when you want to charge the car. For people with Time Of Use rates, this is easy because you just set the PW configuration to match your rate schedule and set the car to charge during the cheapest times. If you don't have TOU rates, you could just fake it, defining an Off-Peak from say Midnight to 6am and set the car to charge during that window. If you want the batteries to power the house but not the car during that time, then it gets more complicated.

2. The grid is down and you don't want the PWs to discharge into your EV. As long as your EVSE circuit is outside the Tesla Backup Gateway, it will lose power when the grid goes down and it will be impossible for the car to discharge the batteries during a grid outage.

The complicated part:
If you want to run Self Powered and use the solar and batteries for everything EXCEPT EV charging, then you have to put your EVSE circuit(s) outside the Gateway and make sure that the Grid CTs are not measuring the usage of those circuits. If the EVSE circuits are the only things backed up, this is relatively easy because the default location of the Grid CTs are on the grid input of the Backup Gateway. So, the Powerwall system will basically be blind to that usage and it won't be measured at all by the Tesla system and the batteries won't be discharged to offset that consumption.

If you have the V2H bidirectional charger set up and want to use it to extend the runtime of your Powerwall batteries, you have to look very closely at how the system functions and whether it can be grid interactive or if it must be the only power source active on a micro-grid. If it is grid interactive, you have to figure out how it controls how much power is charged and discharged from the EV.

Thank you. I am thinking that nothing prevents us from creating two bidirectional EV charging lines--one that bypasses the Gateway, and one that does not. Then I can choose and be prepared for a second EV some day. . .

 

[BrettS]

Thank you. I am thinking that nothing prevents us from creating two bidirectional EV charging lines--one that bypasses the Gateway, and one that does not. Then I can choose and be prepared for a second EV some day. . .

V2G gets somewhat complicated as if it is going to be used to power your house it will need an automatic transfer switch to prevent power from feeding back into the grid when the grid is down. This is going to make your powerwall installation much more complicated as they will need to figure out how to include that transfer switch and how to utilize the power coming from your vehicle. It will be similar to powerwall installations in houses that already have generators. It can be done, but it gets complicated quickly.

Trying to add a second V2G charger, especially one that would not be part of the powerwall solution is going to make things much much more complicated.

This is definitely not as easy as just installing another car charger.