You have good questions. I don't have the experience to answer them with any certainty or authority. All I know is that other PW2 customers have had soft start hardware added to their A/C compressor circuits and it works. You should consult the documentation for the soft start hardware to see if they recommend any changes to the circuit breakers. Your existing circuit breaker doesn't pop because they are designed to handle this kind of inrush current.
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Time of Use Power Shifting for Powerwall 2
- Thread starter zanary
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- Powerwall Tesla Energy
SoundDaTrumpet
Member
Waiting for my Powerwall installation to happen, so I wish I had something more concrete to add.
Upon review of the design, I commented to add soft start provisions for my AC units, which were added. Recommend sending a photograph of the nameplate to your Tesla advisor to take care of this. Based upon what I read, Tesla installed the items, so to save them the return trip and to enhance efficiency (their cost), I mandated that this be noted on Sheet 1 in their design. My plan includes two PWs for whole home backup to include two A/C units and EV charge station. The advisor assured me that breakers won't trip and that the units just won't turn on if event both A/C units decide to start together. With both A/C running I get only 8kW of power draw. The nameplates' breaker ratings for each A/C unit are 30A and 50A, which point to the need of a soft start as the steady-state power draw is under 10kW (for 2 PWs continuous). I imagine that the 2PWs' 7kWx2 peak rating will absorb some motor in-rush current from each, not both, during startup. The soft start provision is included in the design to mitigate. How the PWs will perform in the summer will be "it is what it is" and will accept their performance. What I stated above applies to when there is no grid power available (battery backup scenario).
Upon review of the design, I commented to add soft start provisions for my AC units, which were added. Recommend sending a photograph of the nameplate to your Tesla advisor to take care of this. Based upon what I read, Tesla installed the items, so to save them the return trip and to enhance efficiency (their cost), I mandated that this be noted on Sheet 1 in their design. My plan includes two PWs for whole home backup to include two A/C units and EV charge station. The advisor assured me that breakers won't trip and that the units just won't turn on if event both A/C units decide to start together. With both A/C running I get only 8kW of power draw. The nameplates' breaker ratings for each A/C unit are 30A and 50A, which point to the need of a soft start as the steady-state power draw is under 10kW (for 2 PWs continuous). I imagine that the 2PWs' 7kWx2 peak rating will absorb some motor in-rush current from each, not both, during startup. The soft start provision is included in the design to mitigate. How the PWs will perform in the summer will be "it is what it is" and will accept their performance. What I stated above applies to when there is no grid power available (battery backup scenario).
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eml2
Member
Tesla Support page has been updated with a lot of extra info. It clearly states that it will not charged from the grid if you have solar.
Functionality | Tesla
I see they have the word "currently" in there so perhaps it will be an option some day. Also, it says they are designed to qualify for the Federal Investment Tax Credit...but if we get the Powerwalls free, there is no Federal Investment Tax Credit.
Wow, thanks for pointing out all of the additional information at Tesla Support! I see that they've answered many of the questions that we've had on TMC over the last year.
The bottom line is that Tesla has designed the Powerwall to be compliant with the requirements of the Federal ITC for US customers, and with the requirements of SGIP for California customers. I was considering the possibility of not claiming the ITC and charging our soon-to-be-installed Powerwalls from the grid during "super off peak" hours. But we might as well claim the ITC.
Given the active role that Tesla plays in the permitting, approval, and maintenance of each customer-owned Powerwall, I can appreciate that it's in Tesla's interest to maintain compliance at each customer site. It also means that the IRS is less likely to raise concerns and/or conduct audits related to the use of the ITC.
In the future, once products like the Powerwall have gained greater acceptance, perhaps Tesla may allow its customers a bit more flexibility. They'd probably want a signed (and perhaps notarized) agreement from each US customer opting out of the ITC.
same here...I opted out of the ITC hoping to get grid charging capabilities.....I guess will take ITC credit if they are not allowing.
Looks like we're days away from the PowerwallOS 2.0 arrival... They have published screen shots and how we are to configure Time of Use Load Shifting (for non PV owners).
Software versions for Powerwall 2?
Software versions for Powerwall 2?
What would you like to know. i’ve had my TOU functionality for the last 48 hours. Still monitoring to see how best optimize
See also this thread for lots of first-hand reports on time-based control: Time-Based Control?
I've been mostly happy with the functionality although it messed up today and treated the peak period as part-peak for some reason.
I've been mostly happy with the functionality although it messed up today and treated the peak period as part-peak for some reason.
I thought it was just me that had that effect... Between 6pm and 8pm local time (which is peak for me)
What rate is it charging from the grid? I’ve seen reports they charging in backup mode was slow at 1.7kw, is it 5kw with TOU?
Mine was activated on Wednesday night. I setup the times based on the PG&E EV-A program. It's been working perfectly for me. Charging each power at 3.5kw now during the non-peak hours, and discharging during partial peak and peak to run my house.
I've also logged into the PG&E account, and verify it on the usage charts...
I've also logged into the PG&E account, and verify it on the usage charts...
Mine is not charging from the grid since I have solar. During off peak, it is charging at my peak production of up to 5kw from my solar panels (this didn’t happen before prior to TOU—it use to be limited to 3.4kwh). By the way, I have two PW’s
Before ToU support was turned on my two Powerwall charges at a combined 3.5kw so I assume that each was 1.75kw.
Now after ToU was turned OK for me they charged at a combined 7wk so each is 3.5kw.
Note: I have two Powerwall no solar.
So some napkin numbers from about a week of time shifting. 9.5kW solar, dual Powerwall 2 setup. Backup reserve set to 25% at this point, though I started at 50%.
I've used an average of ~ 15kWh of stored energy daily during peak rates. My batteries charge in part-peak on weekdays (7am-2pm part-peak, 2pm-9pm peak) and off-peak on weekends (3pm-7pm peak). So the napkin math looks like the following.
2018 PG&E EV-A Summer Rates (non-Californians might want to sit down for this):
Off-peak: 0.12753
Part-peak: 0.25994
Peak: 0.47334 (!)
[5 weekdays * 15kWh * (0.47334 - 0.25994)] + [2 weekend days * 15kWh * (0.47334 - 0.12753)] =
16.005 + 10.3743 = $26.38/week in savings (summertime).
LMK if I'm doing something wrong here, but that's pretty good. I don't have enough data to guess at how it'll work out in the winter, but this is with my pool pump only running a short period each day to utilize my thermal solar. It provides me some flexibility to run it in the warmer part of the day and not impact rates, but I haven't messed with that yet.
I've used an average of ~ 15kWh of stored energy daily during peak rates. My batteries charge in part-peak on weekdays (7am-2pm part-peak, 2pm-9pm peak) and off-peak on weekends (3pm-7pm peak). So the napkin math looks like the following.
2018 PG&E EV-A Summer Rates (non-Californians might want to sit down for this):
Off-peak: 0.12753
Part-peak: 0.25994
Peak: 0.47334 (!)
[5 weekdays * 15kWh * (0.47334 - 0.25994)] + [2 weekend days * 15kWh * (0.47334 - 0.12753)] =
16.005 + 10.3743 = $26.38/week in savings (summertime).
LMK if I'm doing something wrong here, but that's pretty good. I don't have enough data to guess at how it'll work out in the winter, but this is with my pool pump only running a short period each day to utilize my thermal solar. It provides me some flexibility to run it in the warmer part of the day and not impact rates, but I haven't messed with that yet.
Are those rates "all-in" including distribution, delivery, taxes, etc.?
Here the rates are such that TOU makes no sense at all. (Unless you use a lot of power at night and none during the day.)
The energy only portion:
Basic: $0.07232
TOU: Off: $0.04209, Mid: $0.14587, Peak: $0.19978
Then there is the transmission/distribution charges of ~$0.045 / kWh. on top of those rates.
Both option include a discount of $0.00722 for the first 1000 kWh.
Of course even on the basic plan the all-in cost works out to almost $0.14/kWh.
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It might be worth using the "to Powerwall" numbers to calculate the cost of the electricity you used. The efficiency loss and vampire drain probably are non-trivial. Over the time I've had my Powerwalls (since mid-February), they've imported 427 kWh but only exported 328 kWh according to the gateway's statistics. Presumably 26 kWh went into charging them up initially, but that's still a significant shortfall.
Yes, those are all-in.
You are correct that I'm overlooking that. Using your data point, I'd have to reduce my savings by ~23% due to losses. I'll check out data on that and see if I can get a more accurate count. Thanks. Throwing this napkin away and grabbing another..
