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Review of Two House Solar Installations - 12kW and 8 kW - in SW FL

dfwatt

Active Member
Sep 24, 2018
3,088
5,099
FL
I wish I could afford Solar and a few powerwalls Oh well I guess I'm stuck with my generator. The good thing is I can power a window A/C unit The bad thing is it uses gas Can you charge the power walls through a generator if there is not enough sun for solar after a storm Can I run 220 v items off of the powerwall

At some point Tesla probably is going to offer the rental system in Florida. It's amazing that they don't. This means that you simply get a 4 kW, 8 kW, or 12 kW system and pay either 50, 100, or 150 bucks a month if I'm not mistaken although I may not be remembering those numbers correctly. In any case it's still a good deal.
 

mstgkillr

Member
May 24, 2020
67
47
Cape Coral
On the larger system, why did you only go with 2 Powerwalls? I see that Tesla recommends 3 for that size system. Have you tried running off of the grid for a week or more? I understand the Powerwall can only charge/discharge at 5 kW/Powerwall... so 10 kW for two, and 15 kW for three.

According to PVWatts, the 11.34 kW system should produce a max of 9.45 kW, and a daily max of 68 kWH on the best day of the year. With two Powerwalls, I would only have 27 kWH to get me through periods of non production.
 

dfwatt

Active Member
Sep 24, 2018
3,088
5,099
FL
On the larger system, why did you only go with 2 Powerwalls? I see that Tesla recommends 3 for that size system. Have you tried running off of the grid for a week or more? I understand the Powerwall can only charge/discharge at 5 kW/Powerwall... so 10 kW for two, and 15 kW for three.

According to PVWatts, the 11.34 kW system should produce a max of 9.45 kW, and a daily max of 68 kWH on the best day of the year. With two Powerwalls, I would only have 27 kWH to get me through periods of non production.

I think there's a clear distinction here between optimal-cost-no-object and best value. We've never had any kind of issue with running out of power despite several power outages with two power walls. It's possible that if we had a whole lot of cloudy days and we wanted to run the air conditioning at a high level that we might be bumping up against trouble. But I doubt it based on a minimal 20 kilowatt hour output for the system. We've never used more than about 40-45 kilowatt hours in a day. So if push comes to shove we can turn off the pool turn down the AC and get through a week of days with minimal Sun. If you want to spend the extra 7000 bucks for that third power wall that might help you in a really unrealistic contingency scenario, be my guest. After all, it's your money! We decided not to.

If you do the math it's that 27 kilowatt hours plus whatever your consumption is minus the system's daily output. So let's assume worst case scenario you've got a week of 15 kilowatt hour solar output days. If your Baseline consumption to run at least some air conditioning is 20 kilowatt hours, that means you got a five kilowatt-hour deficit. That means you would literally have to have 6 days in a row of virtually no sun to run out of capacity. This assumes of course that you're not moderating your consumption and you're sticking with the 20 kilowatt hour consumption figure. That seems literally a very unlikely worst case scenario. I'm not sure we've had more than a couple of back-to-back low output days maybe three at most during the rainy season.
 
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dfwatt

Active Member
Sep 24, 2018
3,088
5,099
FL
How are you able to put both systems from each house on the same app? How do you switch between the two?

It's just like if you have two cars. They appear as separate panels that you side swipe to get to. We have two cars so that gives us a total of four panels in the app.
 
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miemrich

Member
Aug 4, 2012
133
25
Cape Coral
Excellent review! Thanks for the post!

I also live in SW Florida (Cape Coral) and just started researching standby generators for hurricane season, which eventually led me to the Powerwalls. I read that South Miami's mayor went off grid for 7 days in a trial run for hurricane season with solar and Powerwalls. I understand Powerwalls, for sustained power outages, is impossible without solar, so here I am.

Tesla.com recommend a 15.12 kW system with 4 Powerwalls, but I'm not sure if I have enough roof space left after the pool solar heating panels. The next size down is a 11.34 kW system with 3 Powerwalls, which should fit, but I would rather due 2 Powerwalls (less expensive) if they would be sufficient for off grid use. Also, even if I had enough roof space left, it would be considered Tier II, which requires additional liability insurance.

After researching the last 12 months of power use, with absolutely no power conservation in place, I used 20,687 kWH. The average, maximum, minimum daily usage was 58 kWH, 113 kWH, and 23 kWH, respectively. This year should be better (long story). I was able to run my entire house without load shedding, including my Trane XV20i 4-ton HVAC (variable system), pool, and well equipment, with the exception of the dryer, range, and hot water heater, on a Honda EU7000is inverter generator rated at 7kW starting and 5.5 kW continuous.

I am considering financing this project through PACE or Telsa, however that works out.
  • How did you get a 12 kW system from Telsa? They only show a 11.34 kW system online.
  • What is your average power consumption at the 12 kW house?
  • How long could you go off grid with decent conditions, during hurricane season?
  • I see that you have an 8 kW system at your rental, which I assume is an investment property... did that system make financial sense? With the smaller 11.34 kW system and 3 Powerwalls, even with the incentives, I am looking at $50/month more than my current average electric bill and I am not sure if it will completely offset my bill.
  • I understand that Tesla doesn't manufacture the PV panels or inverters... can you spec the PV panel and microinverters used?
  • Do Telsa employees perform the work, or is it subcontracted out to a local solar installer?
  • What made you choose Telsa solar over Enphase?
  • I've read some good things about Enphase Enpower...
 

miemrich

Member
Aug 4, 2012
133
25
Cape Coral
Hi, I also live in Cape Coral and have a Solar System on my roof since 12/2014. It's 11.55 kW which keeps it in Tier 1 with LCEC. It consists of 42 panels @ 275W each with SolarEdge Power Optimizer and 1 SolarEdge 11400 inverter. Now 1 Optimizer died on me, but SolarEdge was quick sending me a replacement unit. Unfortunately my installer from 2014 is out of business and I need someone who replaces my optimizer on the roof. Any help out there?

Thank you.
Michael Emrich
[email protected]
 

mstgkillr

Member
May 24, 2020
67
47
Cape Coral
Hi, I also live in Cape Coral and have a Solar System on my roof since 12/2014. It's 11.55 kW which keeps it in Tier 1 with LCEC. It consists of 42 panels @ 275W each with SolarEdge Power Optimizer and 1 SolarEdge 11400 inverter. Now 1 Optimizer died on me, but SolarEdge was quick sending me a replacement unit. Unfortunately my installer from 2014 is out of business and I need someone who replaces my optimizer on the roof. Any help out there?

Thank you.
Michael Emrich
[email protected]

Sending PM...
 

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