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Newbie: 4kw + 1powerwall in progress

Wannaretire

Member
Jul 16, 2020
95
13
94536
Hi!

Thankful to have found this forum.
I have put down my $100 deposit for a 4kw and one powerwall system.

I'm hoping to review the 'quote' and design with the Tesla designer next week. I have got quotes from other solar providers, but Tesla seems much cheaper.

I really want to get honest opinions from folks who have been thru/ going thru the Tesla solar experience. What questions should I ask and what can I do to ensure my experience with Tesla solar is as best as possible?

Some details about my house (let me know what im missing):
Located in zip code 94536 (norcal)
Used roughly 7000 kwh last year
Annual electric bill was just over $2K ($170 ish a month).
I have a new roof, 2 years old...
No shading issues.
Front of our house faces west.

1. I've been sized by other solar providers at a 5.5kw system. I really don't know whether I should oversize and choose the 8kw option with Tesla. I believe with the Powerwall providing energy during peak periods i *should* be good with the 4kw system. Not sure, would love some feedback.

2. Any opinions on powerwall? I am very tempted to proceed with one.

3. Given the limited time I'll have with the designer, what should I ask for to ensure the install and solar operation is optimal. I.e. try to mitigate any shortcuts etc.

I know I'm new here so feel free to ask me questions and point me in the right direction.

Thanks
 

Southpasfan

Member
Jun 2, 2019
461
587
Pasadena
There is no right answer about system size. It looks to me like there are three types of customer.

Those who live in an area where multiple day loss of power is anticipated. If you are in this situation its powerwalls for sure and a larger system than otherwise because the powerwalls need to be charged at the same time as the system is powering the house. Thats the only mathematical way to make it through multiple days.

Lets say you just want to save money. Due to a combination of pricing, efficiency, and low interest rates, any size system should save money. More so depending on how the utility credits over-production. Powerwalls do not necassarily save any money. However, solar alone also goes out when the grid goes out. Some, like me, don't want that even if the power outage was othewise short.

Finally, the third camp is that you want to take advantage of the good pricing and the tech, and see if you can get completely independent of the grid. That involves calculating system plus powerrwalls. 7000 kwh is not a lot per year. Thats only 19kwh per day. As a powerwall has 13.5kwh and an 8kwh system could produce 40 kwh per day you should be fine in summer.

There isn't much advice beyond that. I don't know how you only use 19kwh per day with any significant A/C or electric appliances or a Tesla car (a car alone can use up to 60kwh per day to charge up). If you don't have significant appliances, one powerwall, with its 13.5kwh and 30 amps output might be enough.

Its not enough for our house so I am in the 16.32 system with 3 powerwalls boat.

P.S. There is alot of advice once you decide what size you need, but its too much for one post.
 
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Mardak

Member
Oct 13, 2018
777
1,585
USA
I've been sized by other solar providers at a 5.5kw system. I really don't know whether I should oversize and choose the 8kw option with Tesla.
Do you have a solar panel layout proposal for the 5.5kW system? Might be useful as a reference when looking at Tesla's proposal. How much did the other provider bid for that system? If it's over $16k, might as well just get the 8kW with Tesla.

I believe it defaults to 2 Powerwalls with 8kW, but there's an Edit button to adjust down or up (for panels too).
edit design.png
 

getakey

Active Member
Jan 28, 2020
1,413
451
95762
5.5 kW seems right, but Tesla won't customize?. I used 15000 kWh and have a 11.8 kW system. Annual true up was $50.
8 kW will probably over generate and you won't get anything for that assuming you are PG&E.

Going with the PW will help your True up with the 4 kW system
 

kpinthebay

Member
Jun 24, 2020
134
116
San Francisco Bay Area/Kaka'ako
I am just up the 680 from you and like you started out with a 4kw system. I later added 2 extra panels and a Powerwall. I figured since they offered a $2500 package discount and you also get the 26% federal tax credit for the entire system, I just bit the bullet. You'll be on a Time of Use plan anyway, so you will benefit from using your PW during the peak times when most of you are home from 3-9. Outside of summertime, you'll be on partial grid from 5pm on without a PW.

Just checking but you did get the lower pricing for the small system, right?
 

sleevemedia

Member
Jul 1, 2020
57
41
Orlando
3. Given the limited time I'll have with the designer, what should I ask for to ensure the install and solar operation is optimal. I.e. try to mitigate any shortcuts etc.

Unless you've found a magic passageway somewhere, hacked the phone system, or you're driving to Vegas, the design team sits behind the advisors and is not customer-facing. You'll more likely make contact with advisors, plural, as there is no account ownership in their advisory sales team. They take good notes, and I've never had a problem dragging any advisor through my umpteen questions, but ultimately they're there to help you part with your money.

No Powerwalls for me, but I've looked at the California math and they make sense there.

I think my water kettle uses more than 7000 kWh...
 

jboy210

Supporting Member
Supporting Member
Dec 2, 2016
5,395
3,347
Northern California
I am just up the 680 from you and like you started out with a 4kw system. I later added 2 extra panels and a Powerwall. I figured since they offered a $2500 package discount and you also get the 26% federal tax credit for the entire system, I just bit the bullet. You'll be on a Time of Use plan anyway, so you will benefit from using your PW during the peak times when most of you are home from 3-9. Outside of summertime, you'll be on partial grid from 5pm on without a PW.

Just checking but you did get the lower pricing for the small system, right?


Completely agree about the PW, especially with Time of Use plans. I am also up 680 from the OP, in Pleasanton. And can cover my entire usage on summer days including A/C with 2 PWs assuming I open windows to catch the morning breezes and pre-cool the house for the day
 

Ampster

Active Member
Oct 5, 2012
1,802
485
Kenwood, California
I am not clear on the price difference between the 5.5 kW system price and the 8 kW system quote from Tesla?
I did review the other thread and if I understand it the 5.5 kW LG system was priced at $20,000 and the Tesla 8 kW system was priced at $16,000. If that is correct it would seem the Tesla system is the better value. The question about whether you buy the Tesla 4 kW or 8 kW system should relate to your goals and particularly how much of your consumption you want to offset. The biggest variable is the orientation of your roof. I understand the front of your house faces east.

Are there any roof surfaces that face south? Has any installer given you a layout sketch? I used Google Project Sunroof to initially evaluate my roof surfaces for solar potential. Fortunately I had lots of south facing roof. Another resource that I used to check the output estimates of the installers was PVWatts. That is a tool you can use to see what the annual production might be for a particular system. If I understand it correctly you consume about 7,000 kWh a year. A crude estimate of the estimated output of a 4kW system facing south would be about 4,800 kWhr per year. If your orientations are east and west it could be less.
 
Jun 22, 2017
527
337
Bay Area, California
@Wannaretire Do you have an electric vehicle (EV)? or air conditioning (A/C)?

I would recommend oversizing solar and getting the 8 kW system. The costs is about $0.05/kWh over 25 years. The Tesla prices are very cheap today. I paid double back in 2016. Anything over 5.5 kW is tossing money away, but owning solar tends to cause owners to consume more electricity (sad fact maybe?), and there are California incentives for electrification of water heating coming in 2021, which will increase electricity consumption. You might even drop kick the gas dryer.

If you nod your head in the future and get a Powerwall (PW) battery system, the time-of-use rates in California (doesn't matter if you are PG&E or not, public utilities commission (PUC) governs all) will shift you to rate schedule that pays pennies ($0.15/kWh) from midnight until 3pm. Be prepared for negative rate arbitriage.

I think 2 PW systems are easier to implement, and 3 PW systems easiest to implement if you have A/C. Having 2 PW and 4.3kW solar; I wished I had an extra 1kW, but it's too expensive add-on (poor value). I use about 7000 kWh and I wish I had 3 PW to cover peak energy rates from 2-9PM. Next year my grandfathering ends.
 
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Wannaretire

Member
Jul 16, 2020
95
13
94536
@Wannaretire Do you have an electric vehicle (EV)? or air conditioning (A/C)?

I would recommend oversizing solar and getting the 8 kW system. The costs is about $0.05/kWh over 25 years. The Tesla prices are very cheap today. I paid double back in 2016. Anything over 5.5 kW is tossing money away, but owning solar tends to cause owners to consume more electricity (sad fact maybe?), and there are California incentives for electrification of water heating coming in 2021, which will increase electricity consumption. You might even drop kick the gas dryer.

If you nod your head in the future and get a Powerwall (PW) battery system, the time-of-use rates in California (doesn't matter if you are PG&E or not, public utilities commission (PUC) governs all) will shift you to rate schedule that pays pennies ($0.15/kWh) from midnight until 3pm. Be prepared for negative rate arbitriage.

I think 2 PW systems are easier to implement, and 3 PW systems easiest to implement if you have A/C. Having 2 PW and 4.3kW solar; I wished I had an extra 1kW, but it's too expensive add-on (poor value). I use about 7000 kWh and I wish I had 3 PW to cover peak energy rates from 2-9PM. Next year my grandfathering ends.
Hi Thanks!
No electric car yet. We have ac, but don't run it much. Maybe a max of 2 months a year. Im going to upload a pic of the Tesla design I got today. Estimated power production is 6000kwh a year.
 

Ampster

Active Member
Oct 5, 2012
1,802
485
Kenwood, California
Lots of southern facing panels. 6000 kWhr a year is aggressive but possible. I am not sure where you could have put the larger system except on orientations that would not produce the same 1500 factor as this design.
 

jboy210

Supporting Member
Supporting Member
Dec 2, 2016
5,395
3,347
Northern California
With a single PowerWall, you may not be able to run an air conditioner when operating off grid, even if a "soft start" has been added.
Bob is correct on this. A single Powerwall is limited to providing 5kW of continuous power. This removes most high consuming devices from backup such as A/C, oven, dryer, etc. It also requires rewiring to isolate the critical items to backup from the rest of the home.
 

Wannaretire

Member
Jul 16, 2020
95
13
94536
Lots of southern facing panels. 6000 kWhr a year is aggressive but possible. I am not sure where you could have put the larger system except on orientations that would not produce the same 1500 factor as this design.

Thanks Ampster. I had similar thoughts, especially on 'where would I put a larger system?' Cheers...
 
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Wannaretire

Member
Jul 16, 2020
95
13
94536
You could order the Medium system, and then drop panels to fit what you can on your roof. You are not locked into 12 or 24. I would definitely go bigger if it were me. The incremental cost is very small.

Fair thoughts. Where would you put the additional panels? I'll see what the Tesla reps to an idea like yours
 

Wannaretire

Member
Jul 16, 2020
95
13
94536
Bob is correct on this. A single Powerwall is limited to providing 5kW of continuous power. This removes most high consuming devices from backup such as A/C, oven, dryer, etc. It also requires rewiring to isolate the critical items to backup from the rest of the home.
Thanks. Im not too concerned about avoiding high consuming devices during an outage. The rewiring comment concerns me, where can I find out more? Cheers
 

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