Tesla Solar Roof

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randomguy
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Re: Tesla Solar Roof

Post by randomguy » Fri May 12, 2017 11:34 pm

tagius wrote:Most of you are not comaparing apples to apples in this discussion. You are looking at the cost of a Tesla Roof compared to a simple Asphalt roof.

The cost of a Tesla Roof is equal to the cost of a asphalt roof + Solar Panels. I have run the numbers on my house in SoCal and they are almost equal, so all this talk of the Tesla Roof being 10X and 20X the cost of ashphalt shingles is just not correct. Also note that it only works after you figure in the 30% fedral tax credit. You cannot deduct the fedral tax credit from ashphatl shingles, only the solar panels in a conventional set up. With Tesla you can deduct 30% from almost the whole bill. This is where the price really comes down and meets with the conventional set up for solar.

Numbers...Tesla is actually Cheaper
Conventional set up; Shingles 15,000 + Solar Panels 48,000 (18kWh system)= 63,000 less Fed Credit (30% of 48,000...14,400) = 48,600 Total
Tesla roof; 66,300 less Fed Credit (30% of almost entire system...17,900) = 48,400 WINNER

It is surprising to me that they have no data on the website as to how many kWh the system produces or how it is constructed. I just paid the deposit online so lets see what happens. Its fully refundable. I wont actually purchase it unless they can prove it will generate the amount of kWh I need.

2,500 sf roof with no power walls.
Net erned over 30 years; 57,400
Average current electric bill; 220 per month
The question is with the tesla one are you buying a 18kWh system or a 9? I definitely couldn't find that info either. Musks original quote was that it would be cheaper than an traditional shingle roof. The math there was you would pay 60k more for the roof upfront an generate 60k+ of electricity over the next 30 years so it would be "cheaper"

Mudpuppy
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Re: Tesla Solar Roof

Post by Mudpuppy » Sat May 13, 2017 1:11 am

tagius wrote:Most of you are not comaparing apples to apples in this discussion. You are looking at the cost of a Tesla Roof compared to a simple Asphalt roof.

The cost of a Tesla Roof is equal to the cost of a asphalt roof + Solar Panels. I have run the numbers on my house in SoCal and they are almost equal, so all this talk of the Tesla Roof being 10X and 20X the cost of ashphalt shingles is just not correct. Also note that it only works after you figure in the 30% fedral tax credit. You cannot deduct the fedral tax credit from ashphatl shingles, only the solar panels in a conventional set up. With Tesla you can deduct 30% from almost the whole bill. This is where the price really comes down and meets with the conventional set up for solar.
People are comparing the Tesla Solar Roof to traditional roofs without solar panels because that's what Musk re-tweeted in the lead up to the Solar Roof reveal. From Musk's Twitter account:
Elon Musk Retweeted
Electrek.Co‏ @ElectrekCo May 10

Tesla releases details of its solar roof tiles: cheaper than regular roof with 'infinity warranty' https://electrek.co/2017/05/10/tesla-so ... -warranty/
Of course, if you go to that article and look at the infographic provided, it shows that the non-solar Tesla tile is cheaper than a regular roof tile, but more expensive than asphalt shingles.

So as with many marketing items, in the effort to create a buzz, some Tweets were sent out. But in this case, "less" (Tweets instead of press releases) was not "more", unless one considers "more" to mean more confusing, which indeed it was.

VaR
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Re: Tesla Solar Roof

Post by VaR » Sat May 13, 2017 5:39 pm

I have to admit that I like the look of their roofs. It looks way better than my current asphalt shingle roof.

I don't think it makes sense for me to get such a nice-looking new roof for my place, but I'm sure that folks who care what their house looks like from the outside will consider getting the Tesla Solar Roof instead of the ugly solar that you can get now.

In fact, I could see architectural committees mandating the use of Tesla Solar Roofs in swanky neighborhoods.

BTW, it's definitely worth playing around using the "Edit Assumptions" feature. You can set it to 0% solar and see what the roof itself will cost, then add solar to see what the cost is of the actual solar shingle system. You can even compare to Google's Project Sunroof to see what the assumptions are about the solar production of your system.

One of the guys at work already put in a reservation for one.

harikaried
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Re: Tesla Solar Roof

Post by harikaried » Mon May 15, 2017 12:40 am

Using the numbers from before of $5/sqft asphalt, $55/sqft asphalt+solar panel, $11/sqft Tesla non-solar tile, $42/sqft Tesla solar tile; assuming the same solar efficiency (unknown), if one were wanting to replace the whole roof and add solar, it would be cheaper to go with Tesla tiles if more than 32% of the roof would be used for solar.

Now the question of if someone should install solar is the same question as before the Tesla tiles and generally boils down to "is electricity expensive?" and "is there enough sunlight?"

Again using Tesla's calculator with 2000sqft roof with 50% solar, these are the top 10 states for "net earned over 30 years":
  1. Hawaii $91,000
  2. California $44,000
  3. Rhode Island $33,300
  4. Connecticut $33,200
  5. Massachusetts $31,200
  6. New Hampshire $25,800
  7. New Mexico $23,500
  8. New York $21,500
  9. Vermont $20,200
  10. Arizona $19,300
Where only New Mexico and Arizona almost are half the electricity costs of most the others, but those two get much more sun that they're "worth it." Hawaii is an outlier in that the electricity there is almost 3x as expensive and gets plenty of sun, so adding energy storage via Powerwalls definitely helps reduce costs in the evenings.

Valuethinker
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Re: Tesla Solar Roof

Post by Valuethinker » Mon May 15, 2017 2:29 am

VaR wrote:I have to admit that I like the look of their roofs. It looks way better than my current asphalt shingle roof.

I don't think it makes sense for me to get such a nice-looking new roof for my place, but I'm sure that folks who care what their house looks like from the outside will consider getting the Tesla Solar Roof instead of the ugly solar that you can get now.
It's very strange to call it "ugly solar". Is this a common sentiment in USA? Unless you are in a Conservation Area (where it would be prohibited) I'e never heard of anyone in the UK (or Europe) calling solar panels "ugly solar". Rather, it's usually seen as a sign of being forward thinking & modern.

(we do have huge arguments here about utility scale solar arrays in fields-- personally I don't see the objection, but there are plenty).
In fact, I could see architectural committees mandating the use of Tesla Solar Roofs in swanky neighborhoods.

BTW, it's definitely worth playing around using the "Edit Assumptions" feature. You can set it to 0% solar and see what the roof itself will cost, then add solar to see what the cost is of the actual solar shingle system. You can even compare to Google's Project Sunroof to see what the assumptions are about the solar production of your system.

One of the guys at work already put in a reservation for one.
I still think it's too early. You can take a solar panel array off the roof easily enough when more efficient technology becomes available. And people will. Analogy to my LED lightbulbs 5-6 years ago. Although I saved energy by installing them, costs of the danged things have fallen so fast it would have paid to wait :oops: C'est la vie :? :wink:

Solar probably won't increase efficiency that fast, but in 10-20 years time we will be ripping down perfectly good arrays, and replacing them with ones with twice the efficiency, I suspect. "repowering" as they say in the utility business (as in repowering wind or hydro electric stations).

Valuethinker
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Re: Tesla Solar Roof

Post by Valuethinker » Mon May 15, 2017 2:33 am

harikaried wrote:Using the numbers from before of $5/sqft asphalt, $55/sqft asphalt+solar panel, $11/sqft Tesla non-solar tile, $42/sqft Tesla solar tile; assuming the same solar efficiency (unknown), if one were wanting to replace the whole roof and add solar, it would be cheaper to go with Tesla tiles if more than 32% of the roof would be used for solar.
I am guessing no one would replace the whole roof and cover it *all* with solar? You replace the south facing part of the roof, and maybe the east and west, depending on orientation of the house?
Now the question of if someone should install solar is the same question as before the Tesla tiles and generally boils down to "is electricity expensive?" and "is there enough sunlight?"
Buried in there is an assumption about efficiency and energy yield, of course (stating that: I am pretty sure you know that). For example I get about 850 kwhr per annum for 1 kw peak capacity solar panels. That's at 51 degrees N, in a maritime climate (London, England)-- which is not as cloudy and rainy as people think (but is very variable).
Again using Tesla's calculator with 2000sqft roof with 50% solar, these are the top 10 states for "net earned over 30 years":
  1. Hawaii $91,000
  2. California $44,000
  3. Rhode Island $33,300
  4. Connecticut $33,200
  5. Massachusetts $31,200
  6. New Hampshire $25,800
  7. New Mexico $23,500
  8. New York $21,500
  9. Vermont $20,200
  10. Arizona $19,300
Where only New Mexico and Arizona almost are half the electricity costs of most the others, but those two get much more sun that they're "worth it." Hawaii is an outlier in that the electricity there is almost 3x as expensive and gets plenty of sun, so adding energy storage via Powerwalls definitely helps reduce costs in the evenings.
I do know with Hawaii there is effectively a ban on new connections due to grid loading? So the Powerwall feature would be all-important-- you won't be able to sell back to the grid?

Vague memories Arizona is in a similar situation due to political rulings (I remember Nevada, not sure where it got to with AZ).

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Pajamas
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Re: Tesla Solar Roof

Post by Pajamas » Mon May 15, 2017 8:11 am

tech_arch wrote: Tesla estimate: 40% covering our roof, $98,200 before federal tax credit of $21,100 (no Powerwall.) They estimate $17,100 earned over 30 years plus you get a new roof. Excluding the rest of the roof, that's about $70k for their solar tiles.
This article indicates that the Tesla calculator may be making misleading assumptions and omissions: that it assumes the entire cost of the roof rather than just the solar-related portion is eligible for a tax credit, that it omits opportunity costs, and that it assumes the roof will last not nearly as long as the calculator that it will and will have to be replaced.

https://webcache.googleusercontent.com/ ... clnk&gl=us

tech_arch
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Re: Tesla Solar Roof

Post by tech_arch » Mon May 15, 2017 8:16 am

Pajamas wrote: This article indicates that the Tesla calculator may be making misleading assumptions and omissions: that it assumes the entire cost of the roof rather than just the solar-related portion is eligible for a tax credit, that it omits opportunity costs, and that it assumes the roof will last not nearly as long as the calculator that it will and will have to be replaced.

https://webcache.googleusercontent.com/ ... clnk&gl=us
What, the marketing materials may be misleading? I'm shocked!*

*This is why when we went solar we ran our own numbers that seemed more realistic rather than the installer's canned presentation. Unsurprisingly, my calculated ROI was about a year longer than theirs, but the idea of maybe losing the 30% tax credit was enough to convince us to do it now.

TBillT
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Re: Tesla Solar Roof

Post by TBillT » Mon May 15, 2017 9:29 am

...the new Prius Prime Plug-in Hybrid comes with a solar roof option - quite sadly not currently available for the USA market. However, it is an extraordinary engineering accomplishment (I feel) in that it can generate (if I remember correctly) up to 10% of the miles driven without trying too hard.

That is fantastic if you are a country like Japan with limited fossil fuel and limited electricity...how about a car that runs without gasoline or electric supply? (at least some of the time)

harikaried
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Re: Tesla Solar Roof

Post by harikaried » Mon May 15, 2017 10:12 am

Pajamas wrote:that it assumes the entire cost of the roof rather than just the solar-related portion is eligible for a tax credit
Well, that's very easy to check. Put in a roof of 1000sqft and here are the tax credits based on percentage of solar on roof:

0%: $0 tax credit
10%: $1,300 tax credit (roughly 30% of $42 * 100)
20%: $2,500 tax credit
30%: $3,800 tax credit

So no, that article looks to be wrong for that concern. In general Seeking Alpha seems to have many "short Tesla" articles.

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Pajamas
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Re: Tesla Solar Roof

Post by Pajamas » Mon May 15, 2017 3:33 pm

harikaried wrote: So no, that article looks to be wrong for that concern.
Could be, I don't really know anything about it.

Consumer Reports points out that there can be state tax credits that Tesla is not including in the calculations:

http://www.consumerreports.org/solar-pa ... olar-roof/

What if the solar tiles were made of gold? Say, 4 oz. of gold for each tile? Could you still deduct 30% of that up to the amount of your taxable income?

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reriodan
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Re: Tesla Solar Roof

Post by reriodan » Mon May 15, 2017 4:03 pm

I really want one, but just doesn't seem financially worth it yet. May just opt to buy a solar panel at some point.

VaR
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Re: Tesla Solar Roof

Post by VaR » Mon May 15, 2017 9:38 pm

Valuethinker wrote:It's very strange to call it "ugly solar". Is this a common sentiment in USA? Unless you are in a Conservation Area (where it would be prohibited) I'e never heard of anyone in the UK (or Europe) calling solar panels "ugly solar". Rather, it's usually seen as a sign of being forward thinking & modern.
Yes, the USA, home of the backward thinking and old-fashioned HOA (homeowner association). :)

I think the very fact that there are HOAs that actively ban the installation of rooftop solar in neighborhoods implies that there are individuals who either think that:
1. Solar panels are ugly or at least not architecturally consistent with the style of the homes in the neighborhood.
2. That the inconsistency detracts from the value of your neighbor's house.
3. That the inconsistency prevents your neighbors from fully enjoying their property simply be being forced to look at your roof every so often.

I don't understand it myself, though I have experienced this. My neighbor once forced me to uninstall my new split air conditioning system because the external refrigerant line offended his sensibilities.

Valuethinker
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Re: Tesla Solar Roof

Post by Valuethinker » Tue May 16, 2017 3:18 am

VaR wrote:
Valuethinker wrote:It's very strange to call it "ugly solar". Is this a common sentiment in USA? Unless you are in a Conservation Area (where it would be prohibited) I'e never heard of anyone in the UK (or Europe) calling solar panels "ugly solar". Rather, it's usually seen as a sign of being forward thinking & modern.
Yes, the USA, home of the backward thinking and old-fashioned HOA (homeowner association). :)
Land of the Free ;-).
I think the very fact that there are HOAs that actively ban the installation of rooftop solar in neighborhoods implies that there are individuals who either think that:
1. Solar panels are ugly or at least not architecturally consistent with the style of the homes in the neighborhood.
2. That the inconsistency detracts from the value of your neighbor's house.
3. That the inconsistency prevents your neighbors from fully enjoying their property simply be being forced to look at your roof every so often.

I don't understand it myself, though I have experienced this. My neighbor once forced me to uninstall my new split air conditioning system because the external refrigerant line offended his sensibilities.
I suspect also an implicit political bias- -having solar panels, like having a hybrid car, is seen as a "statement". Hopefully as cars like Tesla become more widespread, this will lessen.

In Britain people try to use local planning to stop solar panels. But it's hard to make that stick.

Sorry about your refrigerant line. In the UK where AC at home is almost unknown, it would be the noise factor*. I've even heard of people being told by the Local Council to put a sound reducing housing around a heat pump, then being told, post installation, that it was too noisy and they had to remove the whole installation!

As our summers get warmer there are going to be more of that sort of conflict. Hot summers' eves with no air motion, people just aren't used to having their "serenity" disturbed by AC. Of course they put up with major road noise every day, plus planes landing, but there will be plenty of fights.

They don't call it "little England" for no reason ;-).

* again excepting Conservation Areas. Which can do things like ban satellite dishes.

autolycus
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Re: Tesla Solar Roof

Post by autolycus » Tue May 16, 2017 11:03 am

TBillT wrote:...the new Prius Prime Plug-in Hybrid comes with a solar roof option - quite sadly not currently available for the USA market. However, it is an extraordinary engineering accomplishment (I feel) in that it can generate (if I remember correctly) up to 10% of the miles driven without trying too hard.

That is fantastic if you are a country like Japan with limited fossil fuel and limited electricity...how about a car that runs without gasoline or electric supply? (at least some of the time)
I'm highly skeptical of any solar roof on a car. The surface area is way too small to be of much use. To get to numbers like 10% of miles driven they must be making some very favorable assumptions about driving patterns, sun exposure, etc.

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KlingKlang
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Re: Tesla Solar Roof

Post by KlingKlang » Tue May 16, 2017 11:14 am

autolycus wrote:
TBillT wrote:...the new Prius Prime Plug-in Hybrid comes with a solar roof option - quite sadly not currently available for the USA market. However, it is an extraordinary engineering accomplishment (I feel) in that it can generate (if I remember correctly) up to 10% of the miles driven without trying too hard.

That is fantastic if you are a country like Japan with limited fossil fuel and limited electricity...how about a car that runs without gasoline or electric supply? (at least some of the time)
I'm highly skeptical of any solar roof on a car. The surface area is way too small to be of much use. To get to numbers like 10% of miles driven they must be making some very favorable assumptions about driving patterns, sun exposure, etc.
The Prius Prime Plug-in Hybrid has a battery only range of only 25 miles, then you have to start using the gasoline engine. It's claimed that the solar roof will extend that by another 3.7 miles on a very sunny day.

The car is not currently being sold in the USA because the glass roof won't pass the roll-over test.

squirm
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Re: Tesla Solar Roof

Post by squirm » Tue May 16, 2017 3:29 pm

We have solar panels on our roof, frankly I never considered them ugly, if fact I like seeing them, knowing their producing power with zero pollution.

madbrain
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Re: Tesla Solar Roof

Post by madbrain » Tue May 16, 2017 6:47 pm

tech_arch wrote:[
REC Twin Peaks 290W panels with a Sunny Boy 7.7 string inverter. We're early adopters in our neighborhood and were able to get a good deal for that.
How does a 7.7 string inverter work for a 9kw system ?

You should price the cost of inverter replacement over 25 years, it's likely you will have to do it at least once, if not twice. There is a reason the standard warranty on it is 10 years . Micro-inverters would cost more, but would not need to be replaced, and would also have higher output.

madbrain
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Re: Tesla Solar Roof

Post by madbrain » Tue May 16, 2017 6:50 pm

tech_arch wrote: Am I missing something? Maybe our electricity rates just make it infeasible. Has anybody else priced out their homes?
I have a 9.5 kW DC system in California. The annual savings are $5K. PG&E electricity prices are very high.
I paid much more than your quote, but it was years ago, and use micro-inverters and a combination of Sharp US made panels and some Talesun Chinese made. I first put the Sharp in 2010 and the Talesun in 2012. The system is almost fully amortized now, only a few months away from breakeven. I expect another $100k of energy savings from the system after that.

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Re: Tesla Solar Roof

Post by madbrain » Tue May 16, 2017 6:56 pm

Valuethinker wrote:I had this with LEDs. 6 years ago, at nearly £20 per bulb (say $30) for a replacement for a 50w halogen, it paid to replace-- I had an NPV model that showed this ;-). I pay about 22 cents US for electricity per kwhr.

Lo and behold you can get those same LEDs for below £5 per bulb. Prices fell faster than my savings in energy. It would have paid to wait (interest rates fell to record low levels and stayed there, so the opportunity cost was not huge, but still). :oops: :oops:
Yes. This is why I put 240 CFLs 6.5 years ago to replace the halogens that came with my house. It would have been prohibitively expensive to put LEDs back then. There weren't even LEDs with sufficient comparable lumen output in many cases. I'm just now replacing the CFLs with LEDs, one at a time, as the CFLs fail. The cost is between $1-$5 per bulb in most cases.

surfstar
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Re: Tesla Solar Roof

Post by surfstar » Tue May 16, 2017 10:30 pm

What about the fact that electricity prices could DROP over the next 30 years?

Better and more affordable solar generation and storage. Are these 30 year savings predicated on electricity prices today and increasing with inflation?

Are you entering into a 30 year price contract with the local utility to guarantee your buyback rate?

I haven't looked into these questions, as solar doesn't make economic sense for us, so I'm just throwing them out there.

Valuethinker
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Re: Tesla Solar Roof

Post by Valuethinker » Wed May 17, 2017 5:01 am

surfstar wrote:What about the fact that electricity prices could DROP over the next 30 years?
Until recently I would have said that's impossible. The US electricity grid and many of the power stations were last renewed in the 1970s, and thus are effectively costed at historic cost to the consumer (depending on your assumptions about market structure, etc.). Replacing that at current and future costs will be much greater. Also the US has among the lowest electricity rates of any developed country (in many cases, the lowest)-- nowhere to go but up.

Dieter Helm's latest book is provocative. The spread of new solar technologies (and, eventually, storage) could leave us with a world where (at least in daytime) wholesale electricity is in surplus, and effectively free.

That still leaves grid charges- Transmission & Distribution. These will go up, I am fairly sure. Electricity might be "too cheap to meter" but getting it to (and from) the consumer and handling peak demand won't be, most likely.

But it's a different world than I imagined. Every south facing roof or even wall, in the Northern Hemisphere, could get slatherd in solar cells.
Better and more affordable solar generation and storage. Are these 30 year savings predicated on electricity prices today and increasing with inflation?

Are you entering into a 30 year price contract with the local utility to guarantee your buyback rate?

I haven't looked into these questions, as solar doesn't make economic sense for us, so I'm just throwing them out there.
These are interesting questions.

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Re: Tesla Solar Roof

Post by tech_arch » Wed May 17, 2017 7:31 am

surfstar wrote:What about the fact that electricity prices could DROP over the next 30 years?

Better and more affordable solar generation and storage. Are these 30 year savings predicated on electricity prices today and increasing with inflation?

Are you entering into a 30 year price contract with the local utility to guarantee your buyback rate?

I haven't looked into these questions, as solar doesn't make economic sense for us, so I'm just throwing them out there.
The installers all use worse case scenarios for the rates going up; my analysis kept rates steady. At least for my utility there is no long term agreement for buyback/net metering. It's definitely a risk.

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Re: Tesla Solar Roof

Post by autolycus » Wed May 17, 2017 8:52 am

KlingKlang wrote:
autolycus wrote:I'm highly skeptical of any solar roof on a car. The surface area is way too small to be of much use. To get to numbers like 10% of miles driven they must be making some very favorable assumptions about driving patterns, sun exposure, etc.
The Prius Prime Plug-in Hybrid has a battery only range of only 25 miles, then you have to start using the gasoline engine. It's claimed that the solar roof will extend that by another 3.7 miles on a very sunny day.

The car is not currently being sold in the USA because the glass roof won't pass the roll-over test.
Yeah, 3.7 miles of extra range in ideal conditions is probably plausible. Unless it's a really cheap option, it probably makes no financial sense. If I'm doing the math right here... 3.7 / 25 miles * 8.8 kwh = 1.3 kwh of solar production. At the US average of 12c/kwh, that's 15.6c per day of energy production on an ideal day with the car in the sun and not in a garage or under a tree. $57.05/yr if it has 365 ideal days.

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KlingKlang
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Re: Tesla Solar Roof

Post by KlingKlang » Wed May 17, 2017 9:44 am

autolycus wrote:
KlingKlang wrote:
autolycus wrote:I'm highly skeptical of any solar roof on a car. The surface area is way too small to be of much use. To get to numbers like 10% of miles driven they must be making some very favorable assumptions about driving patterns, sun exposure, etc.
The Prius Prime Plug-in Hybrid has a battery only range of only 25 miles, then you have to start using the gasoline engine. It's claimed that the solar roof will extend that by another 3.7 miles on a very sunny day.

The car is not currently being sold in the USA because the glass roof won't pass the roll-over test.
Yeah, 3.7 miles of extra range in ideal conditions is probably plausible. Unless it's a really cheap option, it probably makes no financial sense. If I'm doing the math right here... 3.7 / 25 miles * 8.8 kwh = 1.3 kwh of solar production. At the US average of 12c/kwh, that's 15.6c per day of energy production on an ideal day with the car in the sun and not in a garage or under a tree. $57.05/yr if it has 365 ideal days.
What you're actually saving is the gasoline needed to drive those extra 3.7 miles. At 54 mpg for the car and $2.26/gallon for gas that's only 14.7c per day. At $4.24/gallon in Japan now you're up to 29c per day.

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Re: Tesla Solar Roof

Post by Valuethinker » Thu May 18, 2017 5:38 am

KlingKlang wrote:
autolycus wrote:
KlingKlang wrote:
autolycus wrote:I'm highly skeptical of any solar roof on a car. The surface area is way too small to be of much use. To get to numbers like 10% of miles driven they must be making some very favorable assumptions about driving patterns, sun exposure, etc.
The Prius Prime Plug-in Hybrid has a battery only range of only 25 miles, then you have to start using the gasoline engine. It's claimed that the solar roof will extend that by another 3.7 miles on a very sunny day.

The car is not currently being sold in the USA because the glass roof won't pass the roll-over test.
Yeah, 3.7 miles of extra range in ideal conditions is probably plausible. Unless it's a really cheap option, it probably makes no financial sense. If I'm doing the math right here... 3.7 / 25 miles * 8.8 kwh = 1.3 kwh of solar production. At the US average of 12c/kwh, that's 15.6c per day of energy production on an ideal day with the car in the sun and not in a garage or under a tree. $57.05/yr if it has 365 ideal days.
What you're actually saving is the gasoline needed to drive those extra 3.7 miles. At 54 mpg for the car and $2.26/gallon for gas that's only 14.7c per day. At $4.24/gallon in Japan now you're up to 29c per day.
Hi, does a Toyota Prius really get 54 mpg -- US gallons? I don't think it gets that per Imperial gallon.

If gas is $4.24/ gal in Japan then it's quite cheap by developed world standards.

https://www.statista.com/statistics/221 ... the-world/

Until solar cells have far higher efficiencies of conversion, I really don't see the point of a roof mounted solar array. Unless your car spends most of the day sitting in a sunlit parking lot? Say 8 hours a day in bright sunshine?

tech_arch
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Re: Tesla Solar Roof

Post by tech_arch » Thu May 18, 2017 12:57 pm

madbrain wrote:
tech_arch wrote:[
REC Twin Peaks 290W panels with a Sunny Boy 7.7 string inverter. We're early adopters in our neighborhood and were able to get a good deal for that.
How does a 7.7 string inverter work for a 9kw system ?

You should price the cost of inverter replacement over 25 years, it's likely you will have to do it at least once, if not twice. There is a reason the standard warranty on it is 10 years . Micro-inverters would cost more, but would not need to be replaced, and would also have higher output.
I asked the installer this question because I didn't know the answer. The inverter is based on the system's derated value, and in our case the derating is 15%. That brings it down to ~7.9kW (290W/panel * 32 panels * .85), which is inside the inverter's range.

I realize the inverter is only warrantied for 10 years and will need to be replaced during the system's lifetime. I didn't see anything in my research that indicated micro-inverters or power optimizers would be useful in my situation; our south-facing roof is clear of obstructions and shade, which is the normal use case.

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vitaflo
Posts: 792
Joined: Sat Sep 03, 2011 3:02 pm

Re: Tesla Solar Roof

Post by vitaflo » Thu May 18, 2017 2:36 pm

VaR wrote: I think the very fact that there are HOAs that actively ban the installation of rooftop solar in neighborhoods implies that there are individuals who either think that:
1. Solar panels are ugly or at least not architecturally consistent with the style of the homes in the neighborhood.
2. That the inconsistency detracts from the value of your neighbor's house.
3. That the inconsistency prevents your neighbors from fully enjoying their property simply be being forced to look at your roof every so often.
And yet every house in my HOA has an ugly satellite dish tacked onto the roof of their house. Somehow nobody seems to have an issue with that. But I guarantee as soon as someone tried to put a Tesla roof on, people would complain because it looked "different".

tech_arch
Posts: 210
Joined: Wed May 27, 2015 11:47 am

Re: Tesla Solar Roof

Post by tech_arch » Thu May 18, 2017 3:56 pm

vitaflo wrote:
VaR wrote: I think the very fact that there are HOAs that actively ban the installation of rooftop solar in neighborhoods implies that there are individuals who either think that:
1. Solar panels are ugly or at least not architecturally consistent with the style of the homes in the neighborhood.
2. That the inconsistency detracts from the value of your neighbor's house.
3. That the inconsistency prevents your neighbors from fully enjoying their property simply be being forced to look at your roof every so often.
And yet every house in my HOA has an ugly satellite dish tacked onto the roof of their house. Somehow nobody seems to have an issue with that. But I guarantee as soon as someone tried to put a Tesla roof on, people would complain because it looked "different".
The Telecommunications Act of 1996 prohibits most restrictions against satellite dishes and television antennas. Florida also has laws preventing HOAs from placing restrictions on rooftop solar; not sure what other states do.

madbrain
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Location: San Jose, California

Re: Tesla Solar Roof

Post by madbrain » Fri May 19, 2017 1:27 am

tech_arch wrote: I didn't see anything in my research that indicated micro-inverters or power optimizers would be useful in my situation; our south-facing roof is clear of obstructions and shade, which is the normal use case.
Do you have any chimneys on your roof ? Even something this small can cause shading issues. One of my panels generates about half the energy of all the others due to a nearby chimney.

tech_arch
Posts: 210
Joined: Wed May 27, 2015 11:47 am

Re: Tesla Solar Roof

Post by tech_arch » Fri May 19, 2017 1:50 pm

madbrain wrote: Do you have any chimneys on your roof ? Even something this small can cause shading issues. One of my panels generates about half the energy of all the others due to a nearby chimney.
Nope :- ) Our southern roof is essentially just one long side with zero shading issues; pretty much 100% ideal!

TBillT
Posts: 278
Joined: Sat Sep 17, 2011 1:43 pm

Re: Tesla Solar Roof

Post by TBillT » Sun May 21, 2017 10:57 am

autolycus wrote:
TBillT wrote:...the new Prius Prime Plug-in Hybrid comes with a solar roof option - quite sadly not currently available for the USA market. However, it is an extraordinary engineering accomplishment (I feel) in that it can generate (if I remember correctly) up to 10% of the miles driven without trying too hard.

That is fantastic if you are a country like Japan with limited fossil fuel and limited electricity...how about a car that runs without gasoline or electric supply? (at least some of the time)
I'm highly skeptical of any solar roof on a car. The surface area is way too small to be of much use. To get to numbers like 10% of miles driven they must be making some very favorable assumptions about driving patterns, sun exposure, etc.

I feel the Toyota solar panel Prime is an interesting science accomplishment.
But I personally would rather have the following solar set up:
(1) Garage roof with a modest solar panel array, elec off-grid to batteries
(2) Garage floor with wireless charging from the battery to the car

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