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Arizona Powerwall Installs

Shibiwan

Member
Jul 22, 2019
47
92
Arizona
I'm just starting to look at putting in solar + PW, and trying to figure out how much power the system actually makes on a typical day.

I average 200-250kWh daily (~15-17kWh peak hourly consumption based off SRP's usage tracking) for a 5300 sqft house. So I sized up a 4x solar + 4x PW system and trying to figure out what the entire thing is going to cost me when all is said and done. I put together some ver basic simulation scenarios and still scratching my head on what a typical 16kw solar install would generate daily in summer.

Tesla has reviewed my quote and I'm reviewing it...

Any advice/input is helpful.
 

miimura

Well-Known Member
Aug 21, 2013
6,262
5,891
Los Altos, CA
I'm just starting to look at putting in solar + PW, and trying to figure out how much power the system actually makes on a typical day.

I average 200-250kWh daily (~15-17kWh peak hourly consumption based off SRP's usage tracking) for a 5300 sqft house. So I sized up a 4x solar + 4x PW system and trying to figure out what the entire thing is going to cost me when all is said and done. I put together some ver basic simulation scenarios and still scratching my head on what a typical 16kw solar install would generate daily in summer.

Tesla has reviewed my quote and I'm reviewing it...

Any advice/input is helpful.
If you want to know how much solar will generate on your house, try out PVWATTS. It is very useful.

PVWatts Calculator
 

miimura

Well-Known Member
Aug 21, 2013
6,262
5,891
Los Altos, CA
Thanks -- already been there and put in some numbers.

Right now I'm still wondering if it'll all be worth it....
That depends on your criteria for success.
Look at the quote and how much it will cost you per month or year and how much your power bill will go down. That will give you an idea of the economic value. For me, the reduction in my utility bills is more than the amortized cost of my solar system, so it was a no-brainer.
 

Kenne74

Member
Mar 6, 2013
131
31
Arizona
It’s been about 1 month with my powerwall and I figured I would post an update on the performance and my thoughts. I have 2 powerwalls and 7.7kw solar system 2 AC units (14 seer older units) and a 2800 sqft home. AC is set to 78 all day. Powerwall set to TBC cost savings 10% reserve. I charge my car at night using the grid. House is approximately 50% green and I would like to get that number closer to 75%.

I work from home so your mileage my vary. I need more solar panels, plain and simple. I’m missing out on the solar in the morning because it spends until 12-1pm charging the batteries. Is it a big deal at 3.8cents a kw no but it annoys me lol. Especially when I never had an grid usage from 8am - 5pm. I use to just suffer with my demand controller turning everything off when it got over 2.9kw. The powerwalls are keeping my peek demand at zero but on the hot days it’s touch and go if the batteries will make it. I’m slowly beginning to trust the software.

I will probably end up adding 2-4 more kw of panels by the end of the year to eliminate my annoyance of not being able to charge the batteries and power the house in the summer. I just need to find a great deal and SVSS doesn’t seem interested in selling me more panels at a reasonable price . Could I use a 3rd powerwall of course but I believe more panels is a better bang for my buck.

Just my thoughts.
 
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Darwin

Member
Jan 12, 2018
75
96
Phoenix, Az
Powerwall set to TBC cost savings 10% reserve.

Most days I hit 8PM with about 30% reserve on my 1 PW (5.6kW PV), but sometimes it's still close on cloudy days. I ended up dropping my reserve to 0% just to be safe for demand management. I only have one 16 seer AC unit. I'm using single shoulder period inTBC Cost-Saving. Are you setting up a peak period or a shoulder period in the app?

Let me know if you find a local installer with a good price on additional panels.
 

brur

Member
Nov 17, 2018
358
202
Prescott AZ
I'm in Prescott, so the Valley is another world. But from here, batteries don't make much sense. As long as I have car charging after 8 pm my bill is nothing.
 

Chancellor32

Member
May 10, 2018
719
485
Queen Creek, AZ
Been active for 3 days now and I am happy to say that my 1PW has all but eliminated my demand peaks during the 2-8pm time slot. Have yet to run further tests on lower temps like 75-76 to see how well battery holds up. I believe with the $3600 rebate from SRP it makes getting a PW much more lucrative and even more beneficial than a demand manager.
 
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Kenne74

Member
Mar 6, 2013
131
31
Arizona
Most days I hit 8PM with about 30% reserve on my 1 PW (5.6kW PV), but sometimes it's still close on cloudy days. I ended up dropping my reserve to 0% just to be safe for demand management. I only have one 16 seer AC unit. I'm using single shoulder period inTBC Cost-Saving. Are you setting up a peak period or a shoulder period in the app?

Let me know if you find a local installer with a good price on additional panels.

I am only using 2-8pm for my peek period. The rest is set to off peak. When I travel/not working from home everything works as advertised but it's due to my ecobee's going away mode at 80 deg. I like to keep it nice an cool when I'm home...

As for extra panels, I hit up SVSS every couple months, but it seems right now a 4kw system from Tesla might be the better deal. I just don't understand their business model I'm practical trying to throw money at them! I'll let the forum know, I'm going to wait until things cool off and people stop thinking about solar perhaps then they might be interested.
 

Chancellor32

Member
May 10, 2018
719
485
Queen Creek, AZ
I am only using 2-8pm for my peek period. The rest is set to off peak. When I travel/not working from home everything works as advertised but it's due to my ecobee's going away mode at 80 deg. I like to keep it nice an cool when I'm home...

As for extra panels, I hit up SVSS every couple months, but it seems right now a 4kw system from Tesla might be the better deal. I just don't understand their business model I'm practical trying to throw money at them! I'll let the forum know, I'm going to wait until things cool off and people stop thinking about solar perhaps then they might be interested.
Are you having an issue with Tesla? SVSS was super great to work with but they were well over $3kw vs Tesla at $2.65.
 

Kenne74

Member
Mar 6, 2013
131
31
Arizona
No issues with tesla, my issue is with SVSS not waiting my money lol. I just want to max my inverter to 130%, but to get the sales guy to answer an email without me having to follow up via a phone call is my first complaint:mad:. My 2nd complaint is the pricing to add additional panels is insane. I understand adding after the fact it is going to cost more but don't quote me the cost of any entire systemo_O for 10 panels. Tesla looks more competitive for a couple thousand more and I get 2x the system size.

Anywho I will probably install another 4kw with Tesla this winter.
 

Darwin

Member
Jan 12, 2018
75
96
Phoenix, Az
I am only using 2-8pm for my peek period. The rest is set to off peak.

It sounds like you've found a good kW/#PW sweet spot for managing demand for your home. If you do become more concerned with your Powerwalls not making it to 8pm, you could try changing your 2-8pm peak period to a shoulder period (the same 8pm-2pm off-peak, with no peak set). I would think your 2 PW's would be able make it to 8pm just fine with plenty of power left over in shoulder.

For me, shoulder periods work almost identically to self-powered mode (focused on net usage zero usage), but unfortunately, in shoulder, the PW just doesn't seem to react super quickly to demand surges. On the down-side, with shoulder, you'll probably have an average daily peak demand of several hundred Watts instead of the zero your probably getting with a peak period, but on the upside, you run less risk of running out of battery before the peak period is over. Shoulder periods with no peak periods also come with their own oddities on my system, like occasional battery discharge in off-peak - which I don't understand. It seems there's always a compromise...

I'm currently using a single 2-8pm shoulder period instead of peak, simply because there's no way my 1 PW could make it to 8pm with a peak period set.
 

Kenne74

Member
Mar 6, 2013
131
31
Arizona
Could you share a screen shot or 2 of your software setup? I'm not fully grasping the shoulder period setup that everyone seems to mention.

Thanks
 

Darwin

Member
Jan 12, 2018
75
96
Phoenix, Az
Could you share a screen shot or 2 of your software setup? I'm not fully grasping the shoulder period setup that everyone seems to mention.

I should have done that to begin with. Here's my 2pm-8pm shoulder period for SRP summer:

Shoulder2-8pm.png
 

SOULPEDL

Supporting Member
Jul 25, 2016
3,125
11,957
Arizona
Pulled the trigger today for 8.19kW solar + 2 PW through Tesla. At first they recommended more solar and 3 PWs to cover 100% demand, but that drags down the ROI because you can't compete with SRP costs during off peak. Next round, they recommended 55% and 2 PWs. As Chancellor points out, 40% is the sweet spot and the first PW is a no brainer. I may be able to do this with only 1 PW but if go over then it's really expensive power from SRP. So that's the game we play.

Here's another thing, I just posted on Nextdoor. Nextdoor is the free private social network for your neighborhood community.
In case you can't see this (without signup or something), I'm claiming (IMHO) that the reason when SRP asks us to pre-chill our homes is because they make money selling electricity (duh). When you pre-chill, you don't just shift demand and save $, but you also increase total demand because of the Laws of Thermodynamics (Heat exchange is faster at a higher temp differential, so you lose energy faster trying to get the house cooler than normal).

Another interesting fact, utility companies have renewable mandates. Seems Arizona is not meeting its mandate and seems congress can grant exceptions, not a very strong sense of urgency here in Az. If they consider making their own farms, their infrastructure also needs to be grown so I bet it's cheaper to have us create our own power and just control how much they pay us for it so they don't lose out $$$.
 

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