Tesla Solar Roof

[jhm]

I suggest we have a tread for more detailed discussions of the Solar Roof product. TMC discussions have revealed that consumers may have difficulty properly valuing a solar roof. Consequently, Tesla investors may well have difficulty valuing this product line as well. So there is much that needs to be clarified. Here are a few questions to get us started.



First question, what is the efficiency of the active portion of a solar roof?

The W/sqft = Efficiency*92.9. So 20% implies 18.6 W/sqft. Unfortunately, Tesla's Solar Roof estimation tool does not seem to give solar value numbers compatible with 18.6 W/sqft.


Second question, how do we separate the cost of the roof from the cost of solar and the cost of storage?

The marginal cost per square foot of solar is $31 = $42 - $11 before ITC, or $18.4 = $42*70% - $11 after 30% ITC. Here we assume the whole roof will be installed with either active or inactive Tesla tiles, so marginal is just the incremental cost of choosing active over inactive.


Third question, how does the Solar Roof cost of roof compare with other roofs?


Forth question, how does the Solar Roof cost of solar compare with other solar?

If the active portion is more that 18.6 W/sqft, then the marginal cost of solar is just $1.67/W before ITC and $0.99/W after 30% ITC. This is highly competitive even with utility scale solar. Too good to be true?


Fifth question, how does inclusion of Powerwalls impact the economics of the solar roof and the optimal portion active? What is the value of storage?

My utility offers no feed-in-tariff or net energy metering, and the Tesla estimation tool shows that adding Powerwalls is essential to optimizing the value of solar.

 

[landis]

Third question footnote, how should the effect of fewer lifetime installations be accounted when comparing cost with other roofs?

Forth question footnote, what might be the solar refurbishment costs at the end of life for the active tiles?

Sixth question, how does transferred cost of gas fuel, to home EV charging, affect the payback timeframe?

Seventh question, how does transferred cost of fossil fuel heating, to electric heat pumps (in northeast if nowhere else), affect the payback timeframe?

 

[Topher]

Fifth question, how does inclusion of Powerwalls impact the economics of the solar roof and the optimal portion active?

It doesn't. Storage is an orthogonal question.

Thank you kindly

 

[ValueAnalyst]

First question, what is the efficiency of the active portion of a solar roof?

The W/sqft = Efficiency*92.9. So 20% implies 18.6 W/sqft. Unfortunately, Tesla's Solar Roof estimation tool does not seem to give solar value numbers compatible with 18.6 W/sqft.

My understanding is that Solar Roof efficiency is slightly lower than panels due to coating to make solar tiles indistinguishable from the rest when viewed from the street.

Third question, how does the Solar Roof cost of roof compare with other roofs?

Solar Roof cost is comparable to that of a tile roof with 50+ year warranty, considering (i) the labor cost of tearing off the old roof, (ii) installing the new roof, (iii) increase in electricity bill that comes with using an all-electric vehicle.

This is enough to generate 25k, 50k, and 100k unit demand for years 2017, 2018, and 2019, respectively, which is what I estimate Tesla can supply max with Gigafactory 2 for the years mentioned.

Fifth question, how does inclusion of Powerwalls impact the economics of the solar roof and the optimal portion active? What is the value of storage?

My utility offers no feed-in-tariff or net energy metering, and the Tesla estimation tool shows that adding Powerwalls is essential to optimizing the value of solar.

Inclusion of a Powerwall is important in states where net metering is not allowed, and since net metering will be phased out across the nation in the coming years, it will be essential everywhere. At this time, however, it is difficult to divide the value proposition of the Solar Roof between the roof and Powerwall as Tesla is selling a solution and the customer is looking at the total cost.

Third question footnote, how should the effect of fewer lifetime installations be accounted when comparing cost with other roofs?

I look at the undiscounted total cost and I assume two installations for the asphalt option including labor cost of tearing up the old one.

Sixth question, how does transferred cost of gas fuel, to home EV charging, affect the payback timeframe?

As a rule of thumb, I use $500 per year increase in electricity bill due to use of a Model 3, and $1,500 per year saved in gas.

 

[gene]

Many people will order the Tesla roof who really don't care about the endless analysis that many are doing. Don;t get me wrong, I appreciate the analysis. Thank you for doing it.

Thankfully, for many industries, people simply buy what they want to own. There are many reasons to want a Tesla roof.

 

[Reciprocity]

First question, what is the efficiency of the active portion of a solar roof?

The W/sqft = Efficiency*92.9. So 20% implies 18.6 W/sqft. Unfortunately, Tesla's Solar Roof estimation tool does not seem to give solar value numbers compatible with 18.6 W/sqft.

I'm not good at math so I wont attempt this. But Tesla is telling you what W/sq ft is when they ask you how much you spend per month on electricity. You just need to back into based on how much is typical in your area and how much sun you get, I think they use project sun roof to determine that. Maybe it will be difficult to determine the average cost of electricity in your area, but you should be able to get close. Either way, its just another data point to add to your existing analysis where you can make some assumptions based on what has been said to date. 20-22% efficiency -2% for the textured/colored glass.

They must know, but maybe they are waiting on production cells that might be higher efficiency then what they have already tested?

 

[Topher]

since net metering will be phased out across the nation in the coming years, it will be essential everywhere.

I doubt it (at least completely). Electric companies can do the same analysis that you are doing, and see that without Net-metering they lose their customers altogether. This is already happening in Germany, and the US electrical company think tanks have published on it as well.

Electric companies can make a business model which involves selling grid access, and storage, or they can go bankrupt. They may not be willing to admit that to themselves yet (not unlike another dying industry), and may try fend off the inevitable with legislation, but it will come. The economies of scale are probably enough to live on. They can far better spread the various decentralized sources and balance the usage. In particular, seasonal storage is a huge issue for anyone trying to go it alone with a home solar + battery system.

Thank you kindly.

 

[Reciprocity]

Third question, how does the Solar Roof cost of roof compare with other roofs?

That question should be revised to read, how much does it cost compared to Solar + replacing your existing roof. If you are looking to upgrade from Asphalt, how much do expect the value of your home to up because you tore off a crappy roof and put on a super sick tile roof. I dont know why I cant get anyone to see the cost is somewhat mitigated by the additional value in much the same way a kitchen remodel does. One major different, you dont have to do a kitchen remodel again in 25 years, but you will need to replace your asphalt roof and it will cost much more then it does today.

 

[Reciprocity]

Fifth question, how does inclusion of Powerwalls impact the economics of the solar roof and the optimal portion active? What is the value of storage?

My utility offers no feed-in-tariff or net energy metering, and the Tesla estimation tool shows that adding Powerwalls is essential to optimizing the value of solar.

My area has an SREC program where I can sell credits to the utilities. Adds up to about $2000/Y for ~12megawatts a year paid out every quarter between now and 2025, though the value of the RECs would probably go down every year as more solar supply comes on line.

 

[jhm]

It doesn't. Storage is an orthogonal question.

Thank you kindly

Actually it is not orthogonal. My utility does not offer any feed-in-tariff. So if I generate more power than I can use, it has zero marginal value, but the capacity had positive marginal cost.


Here is a table of options for my roof with 1566 sqft.

Powerwalls Solar% NetCost ValueOfEnergy
0 _____ 0% ____ $17,200 _____ $0
0 ____ 10% ____ $16,700 ____ $3,400
0 ____ 20% ____ $16,600 ____ $6,400
0 ____ 30% ____ $16,800 ____ $9,100
0 ____ 40% ____ $17,200 ___ $11,500
1 ____ 10% ____ $17,800 ____ $7,200
1 ____ 20% ____ $14,200 ___ $13,700
1 ____ 30% ____ $11,200 ___ $19,600
1 ____ 40% _____ $8,800 ___ $24,800
1 ____ 50% ____ $10,100 ___ $26,400
1 ____ 60% _____ $9,700 ___ $29,800
2 ____ 40% ____ $11,400 ___ $26,100
2 ____ 50% _____ $9,900 ___ $30,500
2 ____ 60% _____ $8,800 ___ $34,500

So let's say I'm already convinced that the roof is worth at least $17,200, the cost of the roof without solar. You can see that adding solar without a battery does very little to lower the cost. This is because my utility pays me nothing for excess. So at most adding 20% without a battery only saves $600 over 30 years. This illustrates why there is so little solar in Georgia; the regulatory environment does not allow solar owners to sell surplus.

But notice what happens when storage comes into the mix. Even at 20% solar, the value of energy goes up from $6,400 to $13,700 with one Powerwall, and the net cost drops from $16,800 to $14,200. But if I'm going to have one Powerwall, I may as well bump the solar up to 40%. This takes value of energy to $24,800 and net cost to $8,800. Indeed, if I was merely interested in saving the most money against buying roof that I value at over $17,200, this combination would cut my net cost in half, the minimal net cost.

On the other hand, if I am motivated to want to generate a lot of clean energy and have lots of backup, then two Powerwalls and 60% would give me the most value for my net cost of $8,800.

The big lesson here is that Powerwalls can make a huge difference in whether rooftop solar can pencil out in Georgia. Even so, it is necessary for a Georgia homeowner to place positive value on the roof itself. If I thought the roof alone was worth less than $8,700, then no amount of solar or storage would make the roof pencil out. I do expect that a basic asphalt roof would easily run me $15k (and I must replace my existing roof within 3 years) and have only neutral curb appeal. I also think that having a Powerwall as backup is worth about $2000 to me, and two Powerwalls (for extra kW power) would be worth $3000 to me. So the active solar is a clever way to help pay for a higher value roof, backup power and the ability to sustain backup power in an extended outage. So I could easily get $20k of combined value at a net cost of $9k. Just like the Model S gave me plenty of reasons to buy even though I'd never save enough on gasoline to pay for it, energy savings do help motivate a multifaceted purchase. I think this will be critical to bringing rooftop solar to Georgia.

So I'd be interested in how others might chose among these options.

 

[mmd]

@jhm ,
I'm quoting myself from another thread. This Forbes article finally does the math right. The power output comes out similar to yours. No surprises here. Also check out the amazing Solarworld hail test video.
'Asphalt roof lasts only 10 years' stuff is just FUD. Here in sunny CA, the main solar roof tile market, there is no hail.

Tesla doesn't have any roof tile product yet; will start pilot production by June. So obviously there are no real roofs to showcase or real specs to publish.
Elon wonders why glass roof is not everywhere. May be he needs to do some research first before starting to collect deposits.
I suspect the customer deposits are declining, so it is time to cover the shortfall with new deposits.

BTW, there are already bunch of solar roof related threads under 'Tesla Energy'. I don't know why you created yet another one.

Finally someone gets the math right on the solar roof tiles.
Why Tesla's Solar Roof Is A Bad Buy

Here is the Solarworld hail test from 2013 (link in that article):

 

[Sudre]

I had a roof put on my house in 2003. If was a 50 year imitation slate (look) asphalt shingle roof.
They removed the old roof.
The cost was a little over $12,000.
That might be a little higher than usual because there were at least 3 previous roofs piled up on my house.

I went to Tesla's site and ran a new roof only for my house and that cost (not including solar) was 11,300.

The size of my roof is irrelevant. The cost for the non-solar roof it CHEAPER than a 50 year asphault shingle roof.

My neighbor (same size house) got the 15-20 year roof because he didn't plan on staying in the house. It cost him around $8000. He was upset when he couldn't sell his house for the price he wanted and the roof was a reason for the lower bids. Overall his resale was much lower because everything he did was on the cheapest budget.
I only mention this because when many people get roofs or do any remodel project they do not care about anything except how cheap the roof/project is. It may cause the masses to not be interested in the Tesla roof but that's all speculation.

As far as solar. I shared this in the investor thread but not as detailed.
I have 12kW on my house and detached garage about three years ago. The upfront cost was about $55k.
The garage has 20 panels. Breaks down to $23for this portion. About 5 kW.
The house has 28 panels. Breaks down to $32k for this portion. About 7 kW
That's without credits and tax rebates.

Tesla's cost is $33,600 for only my house to get 70% solar shingles.

I don't know how to compare this without knowmthe actual kW Tesla is installing.

I would not get the powerwall because I don't see it being worth the cost unless Ameren actually manages to get their way and they force me to pay for the grid at times when I am not using it.

It says I will earn $25,300 over 30 years or $70 a month.
Anyone else want to give it a shot? How much solar is that?

 

[jhm]

That question should be revised to read, how much does it cost compared to Solar + replacing your existing roof. If you are looking to upgrade from Asphalt, how much do expect the value of your home to up because you tore off a crappy roof and put on a super sick tile roof. I dont know why I cant get anyone to see the cost is somewhat mitigated by the additional value in much the same way a kitchen remodel does. One major different, you dont have to do a kitchen remodel again in 25 years, but you will need to replace your asphalt roof and it will cost much more then it does today.

Well, I was trying to separate the value of energy from the value of the roof. I view the value of the energy as helping to pay the cost of the roof.

But we are definitely in agreement that the roof alone adds value to the home. Some of the value is hedonic or aesthetic and some practical. So any potential buyer needs to under what value this has for their family and what possible value this may have for the next home buyer.

I think the hedonic value could be enormous. Some worry about having the first home with something nicer than an asphalt roof, but they don't worry about being the only home on the block with marble counters. I think they will stand out in a good way. We could see a shift in the housing market where homebuyers are seeking out homes with attractive roofs. How many house flipping shows need to place solar roofs before it becomes one of the most exciting ways to enhance curb appeal? And yes, Tesla could advertise on all these home renovation shows, if only with product placement. Asphalt roofs could become more of a negative. They could shout out to all potential buyers, "Look, we got the cheapest roof on the market, which you can replace in 12 years, but really you should check out the lovely appliances on the inside."

 

[Reciprocity]

@jhm ,
I'm quoting myself from another thread. This Forbes article finally does the math right. The power output comes out similar to yours. No surprises here. Also check out the amazing Solarworld hail test video.
'Asphalt roof lasts only 10 years' stuff is just FUD. Here in sunny CA, the main solar roof tile market, there is no hail.

Tesla doesn't have any roof tile product yet; will start pilot production by June. So obviously there are no real roofs to showcase or real specs to publish.
Elon wonders why glass roof is not everywhere. May be he needs to do some research first before starting to collect deposits.
I suspect the customer deposits are declining, so it is time to cover the shortfall with new deposits.

BTW, there are already bunch of solar roof related threads under 'Tesla Energy'. I don't know why you created yet another one.

You are FUD.

CA is one place which also happens to have a tone of Spanish tile. Seas and Seas of Spanish tile as far as the eye can see. Tons of sunlight and heat can also shorten the life of an Asphalt roof and even CA can get hail in a 25 year window. The older your roof, the hotter its been, the more brittle it will be and the smaller the hail will need to be to damage it. But I will agree with that the Solar tile is not for everyone, just a lot people and there is no real competition.

Tesla doesn't have a model 3 yet but that didn't stop 500,000+ people from putting down $1000 for the honor to wait 18 months. You will see a similar commitment from solar roof customers, though a smaller number.

 

[DragonWatch]

I'm not good at math so I wont attempt this. But Tesla is telling you what W/sq ft is when they ask you how much you spend per month on electricity. You just need to back into based on how much is typical in your area and how much sun you get, I think they use project sun roof to determine that. Maybe it will be difficult to determine the average cost of electricity in your area, but you should be able to get close. Either way, its just another data point to add to your existing analysis where you can make some assumptions based on what has been said to date. 20-22% efficiency -2% for the textured/colored glass.

They must know, but maybe they are waiting on production cells that might be higher efficiency then what they have already tested?

I am a hands on learner. And am in the final stages of moving from earned income to full retirement income. When it comes to math, well I probably was and do not remember being voted least likely to succeed back in high school.

In 2013, sold my shell oil stock holdings for Tesla, and towards the end of year, we installed solar panels; we live in the Pacific Northwest. In 2013 the cost was about $22,000 and the only place was on our south facing roof over the garage. We chose not to install a battery system due to cost and to take advantage of net metering. The electric company keeps threatening to reduce net metering payback, but so far it is not too bad. Bottom line once they pull the plug, so will I by buying a powerwall. Now, the felt roof was new in 2005. That means we will have to temporarily remove the solar panels sometime after 2030 to install a new felt roof and reinstall the solar panels and or replace the solar panels. So, no one option is better IMHO. I plan on being around that long, so get over it

We put ourselves into another state of transition by buying what was to be a getaway is fastly becoming our happy place. And our contractor told us last summer we had maybe five years left on our current felt tile roof. The luxury of this lot, the previous owner clearcut the trees on the lot, as did our neighbors to the south. Our house is pretty much half of the roof is fully exposed to the sun all day long. Okay, so the sun seldom shines here and the rain to date is 128% over record rainfalls for the year to date. Big deal Bottom line, we want to replace the roof with a solar roof, and add the powerwall. We are in the process of replanting Doug firs and dogwoods. Those pretty white flowers make my forest beautiful.

Yesterday, while walking through our local Mothers Day vender bender we stopped to talk with the vender that installed our solar panels. They are still pretty much the only game in town. I sadly found out that our panels that were installed almost four years ago are now behind the times:-(

Continuing with our transition story; we down sized out our Toyota truck and Prius for a MX which was received on 31Mar17 Bottom line here is costs of monthly electricity are going up and the costs associated with installing a NEMA 14-50 and a Tesla home charger vs 110v trickle charging. Also, this is the time of year that power companies readjust their bill averaging which we do at both locations. First, I am applying for a $500 rebate at the primary residence since it was offered. Still waiting due to the needed paperwork especially the MX certificate of ownership. Plus the cutoff was 31Mar17, so the chances are slim or weak that I will actually get it. I proactively applied a week before the deadline even though I basically had nothing to show for myself. Second, within the last three weeks both electric bills at both locations increased by about forty dollars a month. Initially I was concerned since the bill at the primary residence went up first and I was concerned it was because they were preempting my billing since I was applying for the $500 rebate. Does not appear to be the case. Third, the cost of installing a NEMA 14-50 at the primary residence was about $750 for two sockets ~ which by the way we/can only have one car at a time plugged into that 50 amp breaker. The second residence will be about $350 install plus the $550 Tesla 24' charger or about $900 ~ still waiting on the bill:-( However, I believe you can daisy chain Tesla chargers (please verify before you buy). The trickle charging method which is essentially no install costs, takes roughly two and a half days to charge back up if you go more than a few miles. Not good for range issues.

Hope you get a charge out of my math

 

[jhm]

Third question footnote, how should the effect of fewer lifetime installations be accounted when comparing cost with other roofs?

Forth question footnote, what might be the solar refurbishment costs at the end of life for the active tiles?

Sixth question, how does transferred cost of gas fuel, to home EV charging, affect the payback timeframe?

Seventh question, how does transferred cost of fossil fuel heating, to electric heat pumps (in northeast if nowhere else), affect the payback timeframe?

Third and fourth, the warranty on the solar is limited to 30 years. Additionally obsolescence could make an earlier replacement desirable, for example, substantially higher efficiency solar cells could give the system more capacity. So my personal view is that roof is desirable for 25 to 30 years, but it may be use as a mere roof for much longer than that.

The sixth and seventh questions relate to how much power a family consumes and whether the roof is sufficient to meet that consumption. If you already consume more power than your roof could possibly produce, then adding more electrical load will not help the economics. But you installed more capacity than use, additional load could improve your utilization. If you don't already have an EV, but think you will after you install your roof, then you'll want to anticipate that need, and it may be worth installing more capacity than you initially need.

Another issue like this is power management for the home. Smart thermostats, smart appliances, etc. can help make better use of solar power as it is being generated. This can help offset some of the need for a battery. For example, it may be better to chill your home before sunset than to run AC on a battery. So I think a solar roof is a really nice gateway to all sorts of home energy management technology.

 

[Snapdragon III]

I am a little too cheap to put a deposit down on the new roof, but I want one bad. Same situation I am in with the Model X. If my current roof, or current car dies, I will probably go ahead.

The option I am lusting for is the glossy modern version. What is people's guess as to how these would look over time in relation to getting dirty? Would you need to get up there every once in a while with a car wash brush and scrub them off. How slippery do you think they would be? Could you safely get up there and clean it? Could you go out to the end of your eaves and clean the gutters, like I currently do dangerously on my composition roof? Does anyone have experience with ordinary solar panels on there roof, and how often they need to be cleaned? What visual, and power generation effect it has?

 

[jhm]

I'm not good at math so I wont attempt this. But Tesla is telling you what W/sq ft is when they ask you how much you spend per month on electricity. You just need to back into based on how much is typical in your area and how much sun you get, I think they use project sun roof to determine that. Maybe it will be difficult to determine the average cost of electricity in your area, but you should be able to get close. Either way, its just another data point to add to your existing analysis where you can make some assumptions based on what has been said to date. 20-22% efficiency -2% for the textured/colored glass.

They must know, but maybe they are waiting on production cells that might be higher efficiency then what they have already tested?

I don't see how to make that work. I'd need to know what utility rate they are assuming. The monthly amount accumulates to more that the value of energy over 30 years including 2% escalator.

I do wonder if the estimation tool build a lot of conservatism into the value of energy estimate.

 

[MP3Mike]

I don't see how to make that work. I'd need to know what utility rate they are assuming.

Then why don't you just look where they tell you they get them from: EIA - Electricity Data

 

[DragonWatch]

I am a little too cheap to put a deposit down on the new roof, but I want one bad. Same situation I am in with the Model X. If my current roof, or current car dies, I will probably go ahead.

The option I am lusting for is the glossy modern version. What is people's guess as to how these would look over time in relation to getting dirty? Would you need to get up there every once in a while with a car wash brush and scrub them off. How slippery do you think they would be? Could you safely get up there and clean it? Could you go out to the end of your eaves and clean the gutters, like I currently do dangerously on my composition roof? Does anyone have experience with ordinary solar panels on there roof, and how often they need to be cleaned? What visual, and power generation effect it has?

I have heard too frequently people say it does not pencil in on different topics. Bottom line buying a solar roof will not pencil in, just as my MX did not pencil in, but I believe in the value of not continuing supporting fossil fuels.

Now to answer your second question here. I wash my solar panels here in the northwest twice a year if at all possible and in addition I will climb up there to remove broken branches from time to time. It would be easy to get pissed at the trees, but our two pine and one cedar are over 100 years old and are homes to birds and squirrels. No my wife does not make me sleep in the tree, even if she thinks I am a bit squirrelly