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Arizona Powerwall Installs

JayClark

Member
Aug 6, 2019
223
181
Arizona
How much are you guys saving off your normal electric bill.
For me with SRP, an 8 kW system would have costed $16 K after rebates, but only save me $500 per year. I don't use that much electricity to begin with, so maybe it's just me. SRP is not solar friendly. The Tesla people told me that the power packs weren't going to help save money as they were mainly for backup power. Their on-line calculator was not sophisticated enough to factor load shifting into the equation. Even their solar calculator had serious bugs - no wonder the unit is struggling. With $2/W installed, they should be doing a lot better.

I'm on track to only spend about 800-$900 for the year with SRP, when my annual spend last year was around $3200 (includes about 500-600 kWh's of charging my wife's volt each month). This cost reduction is only possible with the Powerwall to zero out peak usage on the solar plan. Suddenly SRP seems more friendly when I can be on the most aggressive solar demand plan, but use zero peak demand and zero peak rate kWh's - and otherwise only consume off-peak power at just about the nations lowest off-peak rates - as far as I can find. Although, my system wasn't up and running until after peak summer, so far all my actual numbers numbers have come in better than my conservatively modeled estimates to calculate savings and payoff. (oh, and this is with only a 4.1kW PV system, I put the money into four PWs and took advantage of the SRP battery rebate - given the small PV system I have the expectation in peak summer I'll need the weekend to get the PWs fully recharged when needed).

When I replace about 80% of my driving next year with an second (full) electric car, vs the miles I currently drive in my old truck - that should save me another $2500-$3000 annually on gas, vs compared to what the cheap off-peak electricity will cost me. All of this "saving" was totally impossible for me to do with solar, from an initial cost & pay-off perspective, until the PWs became available in the SRP area this last year. So you are right that SRP was very unfriendly prior to these large battery systems being available, batteries with relatively sophisticated scheduling/mode capabilities (could still improve though) to manage peak loads.

I'm pretty satisfied with the savings and the pay-off rate at this point.

I never use my PW in backup mode, I simply set the reserve during off peak to 50%, and can usually keep it around there on average and still cover peak periods (except for a month or two during peak summer where I'll have to use the whole capacity) - so technically I do still have it for back-up most of the time, but I would have never bought the PWs just for backup. My SRP supplied power has been very reliable. One, maybe two noticeable very short outages (1 minute or less once, and once for a couple hours when a van hit a power line) in 3 years in my Current home before I installed solar - so backup mode did not factor into my calculations for purchasing a PW.
 
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SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
In the SRP you’ll do best with one large shoulder period covering both peak periods (no peak period setting). This is from many hours of studying the PW behavior and trial and error. Or better yet use Darwin’s SmartThings app to automate schedules.

So a schedule like this for Blue/Grey colors, off-peak in Blue? And set to Cost Savings mode I assume?

Blue...|Grey..................|Blue

Thanks for the tip.
 

Chancellor32

Member
May 10, 2018
711
479
Queen Creek, AZ
How much are you guys saving off your normal electric bill.
For me with SRP, an 8 kW system would have costed $16 K after rebates, but only save me $500 per year. I don't use that much electricity to begin with, so maybe it's just me. SRP is not solar friendly. The Tesla people told me that the power packs weren't going to help save money as they were mainly for backup power. Their on-line calculator was not sophisticated enough to factor load shifting into the equation. Even their solar calculator had serious bugs - no wonder the unit is struggling. With $2/W installed, they should be doing a lot better.
Expecting to save around $1000. Summer bills have gone from $280 to $120 now. Key with SRP is too only get a system big enough to offset like 50% of your usage and then keep demand as low as possible. Been working great so far!
 
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Dec 2, 2017
358
339
Arizona
In the SRP you’ll do best with one large shoulder period covering both peak periods (no peak period setting). This is from many hours of studying the PW behavior and trial and error. Or better yet use Darwin’s SmartThings app to automate schedules.
Can you help me understand why a single shoulder period works better than a shoulder at 5a and a peak at 5p? I haven’t tried a single shoulder so you may be correct, but intuitively I would think the Powerwall would prioritize peak over shoulder. In my case, if the battery ever gets into a situation where it doesn’t have enough juice, I’d prefer it to bottom out in the morning because we generally use less power then.
 

JayClark

Member
Aug 6, 2019
223
181
Arizona
Can you help me understand why a single shoulder period works better than a shoulder at 5a and a peak at 5p? I haven’t tried a single shoulder so you may be correct, but intuitively I would think the Powerwall would prioritize peak over shoulder. In my case, if the battery ever gets into a situation where it doesn’t have enough juice, I’d prefer it to bottom out in the morning because we generally use less power then.

I think whether it works for a given home depends a lot on a combination of factors related to home power loads, timing of Solar peak during day, timing of loads, whether or not the whole house is backed by the PW or just some circuits, amount of PV a given home has, and how many PWs. I have small Solar, and relatively large PW capacity, and the entire home is backed up by the PWs (AC and Car chargers), and the single shoulder did not work for me, nor did the morning shoulder, and evening peak.

In both scenarios after multiple attempts they let my house draw from the grid during my shoulder peak windows, triggering a demand charge. We have quite a bit of daytime power usage since my wife and I both work from home. After several attempts I got tired of seeing my house hit the grid during peaks which I want to be absolutely zero during peaks. So for my home and PV/PW setup, I had to go to a single large peak to cover both peak periods and everything in between, and using Darwins app to change reserve before/after peaks to manage PW charging and discharging.

I think if I had more solar either shoulder-window setup could work for me also though. Someday.
 
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dhskiracer71

Member
May 28, 2019
17
14
Fountain Hills, AZ
Can you help me understand why a single shoulder period works better than a shoulder at 5a and a peak at 5p? I haven’t tried a single shoulder so you may be correct, but intuitively I would think the Powerwall would prioritize peak over shoulder. In my case, if the battery ever gets into a situation where it doesn’t have enough juice, I’d prefer it to bottom out in the morning because we generally use less power then.

I‘ll revise my statement as it seems impossible to figure out how the Tesla PW logic works. Everyone seems to have different experiences. So my recommendation is to try different settings and see what works best for you. Probably best to give it a few days for each setting given all the variables involved.
 
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Kenne74

Member
Mar 6, 2013
131
31
Arizona
Out of curiosity has anyone added an additional battery to their current system after they have already had powerwalls installed? I’m curious of what Tesla charges for installation. I see its $7600 on the website, but it doesn’t include everything.

Thanks
 

Chancellor32

Member
May 10, 2018
711
479
Queen Creek, AZ
Out of curiosity has anyone added an additional battery to their current system after they have already had powerwalls installed? I’m curious of what Tesla charges for installation. I see its $7600 on the website, but it doesn’t include everything.

Thanks
Installation costs vary from $2500-$3000 for a PW install.
 

Fonzi03

Member
Nov 11, 2019
26
18
AZ
Figured you all may want to see this also as mine just went live. Here's a powerwall charging from solar and grid at the same time, currently having an issue where it caps out at 1.7kw but they're working on it.

I'm contemplating buying another powerwall and installing myself as at this point it's extremely easy. Just a few wires need to be swapped out to a thicker gauge.
 

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oldpueblo

Member
Apr 4, 2016
82
40
Gilbert
Well I go live on 12/31, just barely squeaking in before the new year. :p I also had them leave space to add a third powerwall in the future (maybe even next year), so I'm glad people are posting about that.
 

SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
Figured you all may want to see this also as mine just went live. Here's a powerwall charging from solar and grid at the same time, currently having an issue where it caps out at 1.7kw but they're working on it.

I'm contemplating buying another powerwall and installing myself as at this point it's extremely easy. Just a few wires need to be swapped out to a thicker gauge.

The only hard part is lifting a PW over the wall plate. I haven't tried it but the rest looks very easy. Just have to make sure the rest of the system is capable (wire sizing, kW ratings etc...). These quotes ($2-3K typical) assume problems, but if it's a shoe fit you'd just be subsidizing the other peoples' installs. Go for it, but no warranty maybe. Might still be worth the risk.
 

SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
So for my home and PV/PW setup, I had to go to a single large peak to cover both peak periods and everything in between, and using Darwins app to change reserve before/after peaks to manage PW charging and discharging.

I think if I had more solar either shoulder-window setup could work for me also though. Someday.

What is Darwins app?
 

SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
Here's my update after 3 weeks. I'm loving this new way of life, it's like camping and trying to make the fire last. The feeling of independence is awesome! I don't like feeding the grid - with current rates, it's a loss. Amazing how just pennies add up! I have freaked out over a nickel... it's all good.

My goals were cost savings + freedom of A/C whenever + less carbon. The A/C freedom may be hurting the first goal but I was OK with this. I have days when I think I should have just got the full 12kW system, but batteries are overpriced but changing fast. Key point, you can't just add more panels to existing systems - voids warranty. Must add a new 2nd inverter, so consider this when sizing, adding on is more costly in the end. But priorities can change.

Scenario:
  • Utility is SRP (Monthly fee $23, super low EV charging rates under 6 cents, but only 2-3 cents for feeding grid per kWh... roughly).
  • Tesla install, 8.19kW PVs (26x Panasonic 315W) and 2 PWs (~27 kWh total storage), ~ $40K complete (before rebates).
  • Based on prior SRP bills, we sized our PVs for 55% of demand, so EV car charging from the grid at night. I'm guessing that 55% was an outcome of matching PV capacity to 2 PWs on our roof/angles. I originally asked for 40% of demand per suggested max ROI, but wanted 2 PWs (in the garage) for the A/C capability (should someone attack our power grid, not so lol anymore).
  • Full home backup (meaning any circuit can run off the PWs, including AC w/o SRP connected)
  • All Panels face a few degrees north of west (good for summer, sufficient for winter)
  • Only 2 people living in a 2,300 sqft 2 story w/ 18,000 gal pool/Jac, I'm a fairly heavy user making stuff + music.
  • Tile roof, 22 yrs old, did NOT redo roof. We'll see... no leaks and just minor peeling on inspection, seemed OK. Neighbors' South facing roofs are falling apart/leaky - suspect it's due to direct sun all day while my tiles are cooked in the PM only.
  • Gas is for central heating, water heater, pool heater, and stove.
  • Installed 2 new A/C 14 seer (scroll motor and load manager). Higher seer not cost effective even with SRP rebates.
  • Model 3 on a 32A/240V, stock charger, low usage. Commute <1mi, but we share the vehicle ~90%.
  • Tesla App - Advanced, Extra-wide peak shoulder 5AM-11PM (self-powered some days when batteries full).
Observations:
  • Lol, I'm checking the app about 20x a day... I hear this is normal when learning.
  • Dec sunny day ~ 22 kWh peak, Ave below was only 18kw due to weather. (68% stored, 2% to grid not by choice).
  • Peak at 2:15PM is 4.3 kW (Keep in mind, I'm facing west, others here are seeing more like 6 kW using 8kW facing south)
  • Everytime I switch settings in Advanced mode, it gives power to the grid before switching. Software?
  • Demand is about par with supply if I leave out the car. I charge the car and run the pool pump 11PM-5AM during super low rates. But I've also gone 2 full days off grid (no car charging). Hard to say given that it's been SO CLOUDY since we powered up in Dec. 2019.
  • Sample size is small and I had 2 large car charges in there, but with that I'm still producing 50% of demand.
  • Hosing off panels increase peak power ~200W. And it just rained a few weeks ago, so it helps.
  • My wireless guitar doesn't like the new wireless Inverter or something. Drops out occasionally now.
  • When the sun is ON, 2PWs charge quickly! So summer sun should easily charge batteries in between A/C cycles.
Wish List:
  • Alert that my batteries are >85% at a certain time of day (so I can hook up the car and charge that too).
  • Stop giving to SRP (software glitch?)
  • Accommodate for 2 peak power schedules.
  • Pigeon mesh around PV skirt (birds love this shade).
  • PV cleaning robot - because we can!
Screenshots of a 1 week window (Dec 30 - Jan 5th 2020):
  • Screenshot_20200111-085702_Tesla.jpg
    Screenshot_20200111-085713_Tesla.jpg
 
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SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
Some glitches for the record. This was captured at 6:21 AM today, but showing data and line at ~ 8PM still. It didn't update for several minutes, switching screens too. Phone was on all night on silent, so should be current.

Screenshot_20200111-062115_Tesla.jpg

Then this little artifact. Seems ~100 watts get thrown around off script.

Screenshot_20200104-131409_Tesla.jpg
 
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SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
Why is it an 8 to 11 week waiting list to get a Model 3. Could it be because of a huge increase of confidence is Full Self Drive. I think of things to say all the time on this board. I don't know how to start a new topic.

Bob, FYI, this is the Az Powerwall thread... no harm.

Guessing you were looking for a page up one level from the investor forum. Tesla, Inc.
"Post New Thread" is on the right side. The investor forum is a thread unto itself so everything there is a reply.

Fire away! But know that new threads can get buried pretty quickly so make a great title!
 

SOULPEDL

Supporting Member
Jul 25, 2016
3,007
11,396
Arizona
Is there a wearables app for Tesla Home Energy to show Battery Level. That should save me about 1 hr a day ;)

I don't see this need going away. For those who set and forget... HOW? There are too many variables and this thing is not smart enough because it doesn't know what I'm doing or planning to do with my power. For example, when laundry day comes, the system has no clue that more loads are coming or to save power the night before by using EV super off-peak. I can go several days off-grid, but intermittent demand (like laundry) requires some planning IMO. Same with changing weather.

So far, my batteries are getting worked hard with large % swings. Assuming all lessons learned on the car battery apply here, so don't keep it 0% for very long, and maybe only charge to 90%. I was also told that 100% is only really 80% and empty is not empty, so I'm assuming the batteries will handle full swings. And because we really only need about 5-10% reserved for outages (never happens here really), I think it's possible my PW will last longer than the car batteries, mainly because my average % in the home is closer to 50% vs more like 75% in the car.

I'm also wondering how many cycles a PW can handle? So I looked up PW2 specs and lifetime is 38MWh in aggregate (vs 5,000 cycles for PW1). So assuming full cycles everyday, 38M/13.5K = 2,800 cycles = 7.7 yrs. I obviously won't go 0-100% everyday, so 10 yrs does seem likely. But does "Aggregate" include power in and out? I'm assuming out only.
 

bpcfi

New Member
Feb 13, 2020
4
0
Mes
Tesla is charging me 1800$ in sales tax on the powerwalls. Arizona srp. I am installing the extra large system with 4 pw at the same time. And they are saying tax is required. I knife think it’s tax tree. Can anyone see there final invoice and see it u paid tax on your power walls or ? Can u post it so I can show Tesla.
 

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