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Tesla Solar and Powerwall Install Complete - SoCal Oct 2021

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
So my install by Tesla finally completed yesterday. I thought I would post an overview since everything seems to have worked out pretty well and we tend to get more posts here about people with problems as you would expect.

My system is 8.16 kW of solar with 2 Powerwall 2's (not +'s). Here is a rough schedule on how the process went.

March - Ordered system
April - On site assessment
April - June - Design churn
July - Permits Issued
August - First Install Attempt - Aborted due to roof condition
September - Reroof
October - Successful Install

I am glad that they stopped the first install, but I wish it would have been caught earlier during the on site assessment. We have only been living here for a couple of years so I didn't know the age of the roof. It looked okay to me maybe slightly marginal, but I am certainly not a roof expert. For the reroof I had to remove my solar thermal pool panels which I did myself. In doing so I really got to see how bad the condition was. As I was removing the anchors the asphalt shingles would easily tear away.

Here is the as-installed layout:

1634324038666.png

There was one change on the day of install. I originally had six panels in a landscape orientation on the west facing 2nd floor roof. They found that the last two panels would not fit so they changed the layout to portrait orientation to fit five panels and moved the last panel to the first story west facing roof. The lead roofer let me know and made sure I was okay with it. He also pointed out the locations where they would bring the conduit up through the roof and made sure I was fine with the locations.

As far as the electrical design, I would have expected them to wire the panels that are on the same elevation and azimuth into the same string but they kept each set of panels on any one roof plane on their own separate string. This means that I have a total of 5 strings so the design included both a 7.6 kW inverter and a 3.6 kW inverter giving an AC-DC ratio <1. I would have thought they would have wanted to save themselves the cost of the extra inverter but maybe there is something else that goes in to that decision.

The install went smoothly other than the slight change in panel layout. The started just before 8 am and didn't finish until about 6pm. Unfortunately being after sunset they were not able to test out the solar fully. They left the solar on and mentioned I was in self consumption mode and would not export to the grid. I thought that was only possible with the Powerwall 2+, so maybe he was mistaken. I didn't say anything since I didn't want him to turn it off. I will see later today or tomorrow when my Powerwalls fill up. The other thing that I didn't get to test is whether my AC will turn on off grid. I will have to test that myself this weekend.

I'm just about at solar noon on my first day of production. So far it's peaked out at 5.8 kW and generated 18 kWh so would expect by the end of the day I will be over 30 kWh which is around my average daily usage when we are not using AC. These numbers seem pretty respectful for mid October.

Now it is onto waiting for inspection and PTO which I am not expecting anytime soon. They will have to refill the permits prior to inspection given the layout change so I would expect it is going to be another month for that to happen and then PTO is anyone's guess.
 

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
As expected once the Powerwalls hit 100% this afternoon the system started to export to the grid. I'm going to have to figure out how to mitigate that in the future. I could go off grid of course but that presents some headaches as I have some non-backed up loads. I also don't know how everything in the house will handle the frequency shifting yet. I might just switch off one of my inverters so that my production is less than my daytime home usage plus powerwall capacity.
 

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
Yeah with the powerwall 2 I don't think there is any way for the powerwall/gateway to talk to the inverters other than raising the grid frequency which obviously can't be done when on grid. I assume with the Powerwall 2+ since the inverter is in the same box there is some type of hardwired communication signal between the two parts.

I texted my wife to use what electricity she could, so she plugged in her car and turned on the clothes washer. That fixed the exporting to the grid for now.
 

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
Sorry to keep replying to my own thread but here is what the first day of production looked like and the powerwalls, gateway, and panel install. Sorry @holeydonut only one blade disconnect.
 

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yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
The AHJ didn't require the Powerwall to be at least 3 feet from the window?
Good question. That particular window goes into our attached garage so at least it is not inhabited living space. That said, the installers were worried that they couldn't fit everything in that space and the backup plan was to move the powerwalls further down the wall which would have put them under a bedroom window. Strange enough the approved plans for the permit had an error and showed that the areal power drop, the meter, and all of tesla's boxes were further down the wall by the bedroom window instead of by the garage. I am kinda trusting Tesla here (haha what could go wrong) that they know what the code is as it will be at their expense if they have to redo it.
 

h2ofun

Active Member
Aug 11, 2020
3,101
678
auburn, ca
Good question. That particular window goes into our attached garage so at least it is not inhabited living space. That said, the installers were worried that they couldn't fit everything in that space and the backup plan was to move the powerwalls further down the wall which would have put them under a bedroom window. Strange enough the approved plans for the permit had an error and showed that the areal power drop, the meter, and all of tesla's boxes were further down the wall by the bedroom window instead of by the garage. I am kinda trusting Tesla here (haha what could go wrong) that they know what the code is as it will be at their expense if they have to redo it.
so the ahj approved, if so, seems you are all set
 

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
I've been thinking of installing at my home and I'm curious what's your expected ROI?
Our current electrical bill is $200-$300 per month so I am expecting to save about $200/month on average. I haven't done the detailed calculation on the ROI, but if you simply look at the breakeven point (i.e at what point have a saved on my electric bills to equal the cost of the system ignoring the cost of the upfront money and lost interest) if I had just gotten solar it is ~5 years. Powerwalls themselves don't actually save you much money given the current NEM. They do help you not buy power at peak times, but when I did that calculation the breakeven point for the powerwalls alone was over 20 years beyond the expected life of the powerwalls. Instead I look at it as the savings from the solar are subsidizing the powerwalls and the breakeven point of the whole system is on the order of 10 years.

I know some people say that looking at the breakeven point is not the way to look at it, but it's easy math I can do in my head.
 
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h2ofun

Active Member
Aug 11, 2020
3,101
678
auburn, ca
Our current electrical bill is $200-$300 per month so I am expecting to save about $200/month on average. I haven't done the detailed calculation on the ROI, but if you simply look at the breakeven point (i.e at what point have a saved on my electric bills to equal the cost of the system ignoring the cost of the upfront money and lost interest) if I had just gotten solar it is ~5 years. Powerwalls themselves don't actually save you much money given the current NEM. They do help you not buy power at peak times, but when I did that calculation the breakeven point for the powerwalls alone was over 20 years beyond the expected life of the powerwalls. Instead I look at it as the savings from the solar are subsidizing the powerwalls and the breakeven point of the whole system is on the order of 10 years.

I know some people say that looking at the breakeven point is not the way to look at it, but it's easy math I can do in my head.
So if your bill was 300 a month, and you saved 200 a month, so you still pay 100 per month? And then you paid the cost of the system? If this is correct, how is there any breakeven point? Or are you saying your produced enough solar to cover you 300 per month, plus send back enough to get credit for 200 per month? This is during both the summer, and winter, when solar produces hardly anything?
 

holeydonut

Active Member
Supporting Member
Jun 27, 2020
2,363
1,706
East Bay NorCal
Sorry to keep replying to my own thread but here is what the first day of production looked like and the powerwalls, gateway, and panel install. Sorry @holeydonut only one blade disconnect.


Yeah that’s crazy they fit all that on the wall lol. You have a solar blade disconnect, but the battery disconnect is on the generation panel in the Gateway (or the little switch on the battery itself). They should put a cool placard on the gateway so a firefighter knows to flip off the breakers in there in order to de energize your home.

Btw, if you have weep holes drilled in your conduit LB’s, I will be jealous 🕳
 

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
So if your bill was 300 a month, and you saved 200 a month, so you still pay 100 per month? And then you paid the cost of the system? If this is correct, how is there any breakeven point? Or are you saying your produced enough solar to cover you 300 per month, plus send back enough to get credit for 200 per month? This is during both the summer, and winter, when solar produces hardly anything?
I'm using very round numbers here and trying to be conservative. Even if my bill was $1M/month and I saved $200/month there would be a point were I saved enough money in comparison to what I would pay without the system to cover the cost of the system.

My bill tends to be in the low $200s most of the year and only jumps to $300 in late July, August, and September when we use AC. I might come close to breaking even in total kWh produced vs consumed over the full year and even more likely to have a net zero energy cost given TOU arbitrage so my savings might be more than I am using for this estimate.

I think it's a good sign that in mid-Oct I generated 38 kWh and my typical home usage when not using AC is around 30 kWh/day. Yes the panels will degrade and get dirty, there will be cloudy days even here in SoCal (especially in May/June), and we still have 2 month until the winter solstice so we will see where I end up over the next 12 months.
 

yblaser

Member
Aug 4, 2018
121
89
South Bay Los Angeles
Yeah that’s crazy they fit all that on the wall lol. You have a solar blade disconnect, but the battery disconnect is on the generation panel in the Gateway (or the little switch on the battery itself). They should put a cool placard on the gateway so a firefighter knows to flip off the breakers in there in order to de energize your home.

Btw, if you have weep holes drilled in your conduit LB’s, I will be jealous 🕳
I forgot about that thread. I checked and they indeed drilled weep holes.
 

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BGbreeder

Member
Jun 19, 2020
496
298
Bay Area
Good question. That particular window goes into our attached garage so at least it is not inhabited living space. That said, the installers were worried that they couldn't fit everything in that space and the backup plan was to move the powerwalls further down the wall which would have put them under a bedroom window. Strange enough the approved plans for the permit had an error and showed that the areal power drop, the meter, and all of tesla's boxes were further down the wall by the bedroom window instead of by the garage. I am kinda trusting Tesla here (haha what could go wrong) that they know what the code is as it will be at their expense if they have to redo it.
Congratulations! (Doubly so on the weep holes! I had to ask nicely for them.)

I believe that you hit the nail on the head. The relevant phrase being "inhabited living space".

I can see that your electrician thinks in unistrut. Nothing is moving there!

All the best,

BG
 

h2ofun

Active Member
Aug 11, 2020
3,101
678
auburn, ca
I'm using very round numbers here and trying to be conservative. Even if my bill was $1M/month and I saved $200/month there would be a point were I saved enough money in comparison to what I would pay without the system to cover the cost of the system.

My bill tends to be in the low $200s most of the year and only jumps to $300 in late July, August, and September when we use AC. I might come close to breaking even in total kWh produced vs consumed over the full year and even more likely to have a net zero energy cost given TOU arbitrage so my savings might be more than I am using for this estimate.

I think it's a good sign that in mid-Oct I generated 38 kWh and my typical home usage when not using AC is around 30 kWh/day. Yes the panels will degrade and get dirty, there will be cloudy days even here in SoCal (especially in May/June), and we still have 2 month until the winter solstice so we will see where I end up over the next 12 months.
My only point over time reading these ROI stuff is one can play with number to get any answer one wants. If one has the money, and taxes, why not go for it,
26% off. But, just put on as many panels as one can fit, and get approved.
 

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