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Time of Use Power Shifting for Powerwall 2
- Thread starter zanary
- Start date
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- Powerwall Tesla Energy
TOU Shifting isn't about programing more than about not pissing off the utility companies and political issues.
At this time - no ability to toggle a discharge of Powerwall 2 to the grid. It only allows of self-consumption.
Back in the early days of solar, inter-ties into the grid, it was specifically FORBIDDEN to have a battery tied PV for this specific reason-- arbitrage. It was under the guise of 'protecting stability of the grid'; but individual houses draining a few batteries isn't even close to the draw of a block of AC units turning on at 6pm when the sun is setting and folk getting home and cranking their units on. This was to protect from TOU arbitrage. Powerwall just made it harder to forbid from the utility companies. Batteries should be fine to discharge and the programming for the shifting really is already in the cars when we choose to program charging the cars.
Electrons don't care if its charging or discharging. It makes no difference. Like all EV/PV systems, the main limiting factor are the AC/DC inverters. This also addresses the earlier concerns of when/how the powerwall is charged -- grid vs PV or either one-- really depends how one sets up the Powerwall and if backup is configured into it. The powerwall CAN setup only charge via PV via a DC connection and then allow the PV system to do the inverting (assuming non microinverters). This maximizes efficiences. I don't know if a backup would be allowed unless the main inverter has this specific property -- most do NOT. Only the newest solaredges have this and that's how the Powerwall 1 was designed to leverage.
Tesla probably wanted a simpler product and not rely on 3rd party products -- hence Powerwall 2 with its built in inverter. I'm curious what they do with multiple Powerwall installations. probably daisy-chain the powerwalls and use a single inverter on the first powerwall. They could easily put in parallel and fully support AC and other higher load, but this would require a reconfiguration of the subpanels and pretty heavy rewiring of exist electrical systems --- easier if you plan original house installs, but not to existing ones.
My understanding of current for current PV+EV owners living in unfriendly SDGE land where Pk hours are now 4pm-9pm.
Optimal setup PV/EV setup TODAY with an existing system -- for backup and charge purposes.
-Install up to 2 powerwalls to max SGIP/ITC - Calculate your 4p-9pm draw needs and determine how much backup is 'safe' -- we use about 10kwh typically those 5 hours.
Schedule
4p-9pm turn tesla apo to full powerwall support: 10kwh of 26 used: - 16kwh remaining
9pm-12am - keep using powerwall support and start charging EVs to get powerwall drained to backup levels (say 6kwh) 10kwh used
12am-600am- turn on tesla app full manual charge -- continue charging EVs. 6hours charge for 2 Powerwalls along with EVs - should be near 100% come 600a
600a-4pm turn tesla app to regular mode. PV starts kicking in and will preferentially charge the Powerwall (but nearly fully charged) then home usage then excess into home grid.
4pm--9pm -- turn tesla app to full powerwall support again.
--The question is how does Tesla record this on the audit of charge/discharge support of the battery -- does the battery show the source of the charge? The discharge still remains solely home consumption. The battery charge is the unknown on the audit trail if ITC ever asks.
At this time - no ability to toggle a discharge of Powerwall 2 to the grid. It only allows of self-consumption.
Back in the early days of solar, inter-ties into the grid, it was specifically FORBIDDEN to have a battery tied PV for this specific reason-- arbitrage. It was under the guise of 'protecting stability of the grid'; but individual houses draining a few batteries isn't even close to the draw of a block of AC units turning on at 6pm when the sun is setting and folk getting home and cranking their units on. This was to protect from TOU arbitrage. Powerwall just made it harder to forbid from the utility companies. Batteries should be fine to discharge and the programming for the shifting really is already in the cars when we choose to program charging the cars.
Electrons don't care if its charging or discharging. It makes no difference. Like all EV/PV systems, the main limiting factor are the AC/DC inverters. This also addresses the earlier concerns of when/how the powerwall is charged -- grid vs PV or either one-- really depends how one sets up the Powerwall and if backup is configured into it. The powerwall CAN setup only charge via PV via a DC connection and then allow the PV system to do the inverting (assuming non microinverters). This maximizes efficiences. I don't know if a backup would be allowed unless the main inverter has this specific property -- most do NOT. Only the newest solaredges have this and that's how the Powerwall 1 was designed to leverage.
Tesla probably wanted a simpler product and not rely on 3rd party products -- hence Powerwall 2 with its built in inverter. I'm curious what they do with multiple Powerwall installations. probably daisy-chain the powerwalls and use a single inverter on the first powerwall. They could easily put in parallel and fully support AC and other higher load, but this would require a reconfiguration of the subpanels and pretty heavy rewiring of exist electrical systems --- easier if you plan original house installs, but not to existing ones.
My understanding of current for current PV+EV owners living in unfriendly SDGE land where Pk hours are now 4pm-9pm.
Optimal setup PV/EV setup TODAY with an existing system -- for backup and charge purposes.
-Install up to 2 powerwalls to max SGIP/ITC - Calculate your 4p-9pm draw needs and determine how much backup is 'safe' -- we use about 10kwh typically those 5 hours.
Schedule
4p-9pm turn tesla apo to full powerwall support: 10kwh of 26 used: - 16kwh remaining
9pm-12am - keep using powerwall support and start charging EVs to get powerwall drained to backup levels (say 6kwh) 10kwh used
12am-600am- turn on tesla app full manual charge -- continue charging EVs. 6hours charge for 2 Powerwalls along with EVs - should be near 100% come 600a
600a-4pm turn tesla app to regular mode. PV starts kicking in and will preferentially charge the Powerwall (but nearly fully charged) then home usage then excess into home grid.
4pm--9pm -- turn tesla app to full powerwall support again.
--The question is how does Tesla record this on the audit of charge/discharge support of the battery -- does the battery show the source of the charge? The discharge still remains solely home consumption. The battery charge is the unknown on the audit trail if ITC ever asks.
Parzival
Member
Multiple Powerwalls have multiple inverters. They just get paralleled. The DC powerwall is discontinued.
strider
Active Member
Ok, hang on. Here's what I want to do for TOU load shifting. Peak time here in the summer is 14:00-19:00 M-F. I don't think I can install enough solar (trees, house is at wrong angle, etc) to power my house during peak times. So I want to be able to charge the PW at night and then during peak hours consume the solar and PW power with the goal of never pushing power back to the grid. Why would that have ANYTHING to do with regulations or agreements? To the utility it will just look like I shut off my house during peak hours and consumed at night. This should help them as the whole reason for peak pricing is because they want to dissuade use during this time.
I understand the utilities not being excited about people buying off peak power and selling peak power but to me that's different then straight TOU load shifting. What am I missing?
I understand the utilities not being excited about people buying off peak power and selling peak power but to me that's different then straight TOU load shifting. What am I missing?
So in your scenario, the utility (at least in California) would typically want to know what you're doing, and would want you to sign a non-export agreement in which you agree that you will never push energy to the grid.
That is actually hard to arrange, as if your Powerwalls are full, and your solar is producing more than you happen to be using at a given moment, you'd need to shut down the solar. Even if you think that would rarely happen, it probably would happen occasionally. The possibility that it could happen would require you to design a system that could handle that case without exporting, or to have an export agreement with the utility.
Cheers, Wayne
That is actually hard to arrange, as if your Powerwalls are full, and your solar is producing more than you happen to be using at a given moment, you'd need to shut down the solar. Even if you think that would rarely happen, it probably would happen occasionally. The possibility that it could happen would require you to design a system that could handle that case without exporting, or to have an export agreement with the utility.
Cheers, Wayne
Parzival
Member
Anyone with Solar and Powerwalls on the grid already has an export agreement in place for solar...
In Australia that is the norm, some areas (depending on the distributor) have either restrictions on the amount of solar on your roof or limits the amount of feed in you can do (a cap of 5kWs for example). As far as a battery goes, there is no restrictions how you use it - you can send it to the grid if you want (check out Reposit Power) but again there might be restrictions to the amount but with the battery you are limited to 5kWs anyway. Personally I have 9.24kW of solar panels and microinverters - and have to restrictions. Electricity retailer is paying me ~$100 a month
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strider
Active Member
Ok, that makes sense. But like @Parzival said, if you have grid-tied solar you're already going to have an export agreement in place for excess solar capacity. So I fail to see what allowing you to charge PWs from the grid at night and then discharge them for your own use has to do with exporting?
The backup gateway knows which direction energy is flowing, loads, etc. It seems trivial to me for Tesla to add a bit of code to the PW/Gateway that says it won't discharge the PW into the grid.
Well, your first post mentioned the "the goal of never pushing power back to the grid," so I was addressing that scenario. I would think that if your utility allows a solar interconnection with export, then they'd allow a solar plus battery interconnection with export, sure.
Cheers, Wayne
Cheers, Wayne
Sure, but the export should never exceed the actual solar production at that moment. This is why I personally want TOU settings so I can prevent PW discharge during the Off-Peak rate period. I want the solar to fill the PWs as early as possible during the day so that there is some Peak Period solar export.
Perhaps my non-use of quoting has lead to some confusion. Both of my last two posts were specifically in regard to the scenario that strider presented.
Personally I'd like the ability to divide the day up into time slices, and for each time slice specify a set of rules concerning power flow and charge level.
Cheers, Wayne
Personally I'd like the ability to divide the day up into time slices, and for each time slice specify a set of rules concerning power flow and charge level.
Cheers, Wayne
Pw2 is simpler... but still to many items to install...
Also they are still limited to 200A ATS.
Also they are still limited to 200A ATS.
This is Tesla promise game. You can predict the actual dates only by amount of "shortness" left in the promises, not by actual promised dates. This is true everywhere, cars, roofs, you name it. In this case, started with 2 months, then a month, then two weeks , and now "shortly", alhtough i am not sure if "shortly" is actually shorter than "early February" promised, excuse me for the pun, shortly after the New Year... The numbers are getting too fine and i start getting lost in rounding errors...
