Tesla Glass Tile Solar Roof Update

[brucet999]

That's certainly a possibility. I'm hoping that the solar roof tiles (size of solar tile -- small) can cover more of the nooks and crannies of my annoyingly and unnecessarily complex roof with actual solar than standard panels (minimum unit size being a very large rectangle) can. My extension is going to have a very simple roof.

Yes, Tesla tiles will give you a lot more usable solar area for three reasons:
1. Because they are small, they can come close to valleys, ridges, and hips.
2. Because they are the roof, they don't have to leave 3 foot-wide firefighter access lanes along the sides and valleys and ridges as with rack-mounted solar arrays.
3. Because of their size, they can surround roof penetrations like vents, stacks and skylights.

Of course, these advantages are useful only if their power per unit area is comparable to panels. One poster here calculates from Tesla's estimator page that they are only about half the output per unit area as standard panels.

Tesla's PowerWall controller includes automatic switching to disconnect key household circuits from the Grid when there is a Grid power failure. Similarly, the inverter disconnects automatically so as not to endanger PoCo workers by back-feeding their wires.

 

[brucet999]

I just had Solar City give me an estimate of $35,000 for 22 panels and 2 power walls plus install,, etc. I went to the roof calculator and it gave me an estimate of $51,000 for a solar roof. That means $16,000 for a new roof. Not too bad for a top quality shingle reroof. It said the roof would be 70% solar shingles. It would be nice to have a breakdown of what they are including.

How big is your roof area?
What percentage of solar for that $51,000?
What is the kW rating of the 22-panel solar array they quoted you?
How do you know the estimator is giving you the same output as the 22 panels they proposed?

I couldn't even get a watts/sq ft spec from a phone call to Solar City.

 

[brucet999]

Is it true the Powerwall needs to be connected to the grid to know the grid 50hz timing. I've read that you have to still be connected to the utility to get that?

If you are generating solar power on a net-metering scheme, then the inverter will only feed AC power when it sees that 50Hz from the power company. It does so because it is sharing the main bus with the power company feed, so they have to be synchronized.

The PowerWall automatically disconnects the circuits it feeds (it can be set up to run all, or only critical circuits) from the Grid when there is a power failure.

 

[AudubonB]

I posted this on April 12 as post #206 in the "Prediction Thread - You Called It".

Now, that's in the Investor Sector, and since I know that many of you avoid that like the tick-infested Zika swamp that it is, I thought some might find it worthy of this thread -

I Predict -

Tesla Energy's solar roof tiles will be agglomerated into panels comprising rows of three, or perhaps four, tiles, extending lengthwise on the order of four to seven feet.
Each tile will - as others have surmised - have its own micro inverter, but it is that whole panel that will be wired in analogous fashion to today's conventional PV panels. This panel will be able to be tilted up along its uphill edge for maintenance purposes; through its micro inverter an individual faulty tile will already have alerted the tech that it, in position B-19, is the bad one, allowing for a super-quick and simple replacement.

I will refine this prediction by suggesting each such panel ought have a "slidable" hinge so that its topmost course of tiles will be able to be extracted from beneath the next course up, prior to being raised.

Such a set-up will reduce the installation costs and times tremendously over the labor-intensive route of affixing each tile individually. Tesla needs prep the sub-roof, including whatever electrical gridwork; then in short order each of these panels - think of them as similar in size to current PV panels - are installed and functioning.

 

[macpacheco]

Why separate micro inverter when in most cases there's a big 380VDC battery and a big inverter on the PW2, inverting and back wastes a lot of electrons. Just stringing enough panels in series so the max voltage the string produces matches PW2 voltage limits seems like a much, much better option.
What seems to make perfect sense is if there are enough panels you can't make a single string, or some panels get shading, it might be better to have multiple series strings arranged, each with its own inverter (allocating the shaded panels separate strings from the other ones).
Arranging multiple panels in series and using the big PW2 inverter reduces ohmic losses in the wiring and inside the panels.
The only exception is if your panels has non uniform shading issues. The reduction in losses might be less than the losses due to some panels getting shade some not, and the whole thing varying according to seasons and time of day.

 

[AudubonB]

I understand your position; mine comes from that in my mind's eye I envision the MPPT of today's "master" inverters as doing a respectable job with the relatively few current PV panels (usually a maximum of a few dozen) but that they would be suboptimal when attempting to manipulate the many hundreds of individual tile PVs. I concede this may not be the case.

I do think, however, that your "stringing enough panels in series..." argument will not efficiently allow either for the varying angles of differently positioned roof gables, etc., nor for tree, etc, shading throughout a day.

 

[miimura]

Why separate micro inverter when in most cases there's a big 380VDC battery and a big inverter on the PW2, inverting and back wastes a lot of electrons. Just stringing enough panels in series so the max voltage the string produces matches PW2 voltage limits seems like a much, much better option.

They need either optimizers or micro-inverters to get reasonable performance on a roof system that will include areas that are sub-optimal. These technologies are usually used at the panel level, which are comprised of 60, 72, or even up to 96 cells. I am under the impression that each tile has a single cell. So, it's not at all obvious how they will do this. They could do cell-level (each tile) optimizers, but as far as I know, it's not been done before.

 

[macpacheco]

For the roof tiles the total power of each tile is likely too small to make sense giving it an individual micro inverter anyways.
Normal top affordable panels produce as much as 450Wp, which then is a little more reasonable for dedicated micro inverters per panel, but a little tile that likely will produce <60Wp each, gee, it just doesn't make sense at all.
I understand the shading problem, but in that case perhaps use a smaller inverter for smaller group of panels, perhaps 3-5 at a time.

 

[timpierc]

If you assume having a roof on your house is an optional thing, cuz its kind of important. If you have a brand new roof, do not tear it off to put this roof on. If you have crappy old, worn dingy tile or asphalt, then the roof will actually add value to your home which you will get back out when you sell it in 7 years. Also when you sell it, you will be including the solar, because you really cant take it with you in this case so you will get 18 years of that value out as well. There is more to it then just the value of electricity generated.

Great coherent argument. Just like there really isn't a premium (there is, but not enough to make up for the upfront cost of a solar system) when you sell your home with solar, this argument is moot.

If I'm shopping for a home, and I see two that are exactly identical in the same neighborhood, but one has a Tesla roof I'll buy it, maybe, for a $10k premium.(And that $10k premium is highly dependent on how net metering policies are going with the utility and state regulators. If it were contentious like it has been in Arizona lately, I'd flat out refuse to pay more for the house because of the solar system. Too much risk in recovering the investment.)

If the seller tacks on an extra $60k to make up for the cost of their Tesla roof because they've only had it for 5 years, and therefore only received $12k in electricity savings, then they're never going to sell that home in the neighborhood. (This assumes $200 electricity bill each month, and the recovery of the federal tax credit. So original roof $100k, now $60k five years later). This is how almost every buyer would treat a home with a Tesla solar roof. It's a nice to have, but you can live without it.
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I highly doubt someone would be able to even get a loan for the house, because it's asking price would be significantly greater than the comps surrounding it. The mortgage company would see it as too risky.

 

[Reciprocity]

Great coherent argument. Just like there really isn't a premium (there is, but not enough to make up for the upfront cost of a solar system) when you sell your home with solar, this argument is moot.

If I'm shopping for a home, and I see two that are exactly identical in the same neighborhood, but one has a Tesla roof I'll buy it, maybe, for a $10k premium.(And that $10k premium is highly dependent on how net metering policies are going with the utility and state regulators. If it were contentious like it has been in Arizona lately, I'd flat out refuse to pay more for the house because of the solar system. Too much risk in recovering the investment.)

If the seller tacks on an extra $60k to make up for the cost of their Tesla roof because they've only had it for 5 years, and therefore only received $12k in electricity savings, then they're never going to sell that home in the neighborhood. (This assumes $200 electricity bill each month, and the recovery of the federal tax credit. So original roof $100k, now $60k five years later). This is how almost every buyer would treat a home with a Tesla solar roof. It's a nice to have, but you can live without it.
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I highly doubt someone would be able to even get a loan for the house, because it's asking price would be significantly greater than the comps surrounding it. The mortgage company would see it as too risky.

I disagree with almost everything you said except one, if the neighborhood won't support the higher price, I agree you won't get the value back out.

But if you upgrade your kitchen it will increase the value of your fine and help sell it. If you only put 1000 into your kitchen then that's the most you will get out, if you have a new asphalt roof it will increase your value because the new owner and appraiser will factor that into their decision. Some goes for upgrading your roof. You won't get every dollar out, but you will get more out for a nicer roof with solar tiles then a cheaper roof with solar. This is a fact, no idle speculation. You need to factor the value of having a much better roof then the one you are replacing. Yes the neighborhood had to support the higher price, many do especially in California where there is a lot of Spanish tile.

As far as the yeah credit, it really depends. If you sell after the credits are gone, there is way for the person your selling to to buy a different house and put solar on for the credit. If you sell before then you have already recooped that part of your investment so why would you need to recoop it from the next buyer? It's s nonsensical argument.

All I'm saying is you need a roof, better roofs are more valuable then lesser roofs. The solar part is a wash, though it might be easier to repair and maintain a solar roof due to the highly module nature, but we need more info to determine that.

Also these tiles appear to be more durable then solar panels on top of your existing roof.

 

[brucet999]

I looked again at the pictures of solar roof tiles with dimensions and completed roof. Plainly the tiles are meant to be laid tight together and each course is laid offset from the course below.

What I don't see is any sort of water channel on one side of the tile to underlap the neighboring tile, similar to what concrete tiles have. If that is the case, then the roof underlayment will get wet whenever it rains, as water will pass between adjacent tiles. The roof underlayment would probably have to be plastic and some sort of channels would have to be placed at the bottom edges of the roof to enable water to run out from under the tiles.

That also argues against mounting on horizontal battens, since they would be perennially wet and soon rot away.

 

[Model 3]

What I don't see is any sort of water channel on one side of the tile to underlap the neighboring tile, similar to what concrete tiles have.

Why would they need that? The titles is overlapping as can be seen on this image:

 

[Reciprocity]

Each tile is actually over 2x as tall so there is no way for the water to go up hill. Also, the tiles protect a roofing material underneath that is water resistant but not durable so the roof protects it.

 

[brucet999]

Why would they need that? The titles is overlapping as can be seen on this image:

These tiles are 14" wide but only 8 1/2" tall, so they only overlap about 1" over the course below. Normal shingles and the Tesla slate tiles are at least twice as tall as wide, so they overlap a bit more than half, thus covering the gaps between adjacent tiles of the previous course.

 

[brucet999]

Each tile is actually over 2x as tall so there is no way for the water to go up hill. Also, the tiles protect a roofing material underneath that is water resistant but not durable so the roof protects it.

Only the slate tiles are two times as tall as they are wide. Smooth and textured are 14" wide x 8 1/2" tall, so no overlap of the sides is possible.

 

[brucet999]

A closer look at the picture on the Tesla Solar site does not show the nailing holes at the top of each tile, so it is possible that the pic also omits a water channel.

 

[Reciprocity]

Only the slate tiles are two times as tall as they are wide. Smooth and textured are 14" wide x 8 1/2" tall, so no overlap of the sides is possible.

I didnt say it was 2x taller then it was wide. I said its over 2x taller then what you see exposed. If what is exposed is 4", then the tile will be 9" tall. This is how it covers the roof with overlap and no way for water to flow up hill. If by chance some does defeat this protection, there is another roof installed under every roof that is thin and light like felt. The top roof protects the felt roof.

 

[brucet999]

I didnt say it was 2x taller then it was wide. I said its over 2x taller then what you see exposed. If what is exposed is 4", then the tile will be 9" tall. This is how it covers the roof with overlap and no way for water to flow up hill. If by chance some does defeat this protection, there is another roof installed under every roof that is thin and light like felt. The top roof protects the felt roof.

In the roof picture, the reveals are twice as wide as they are tall. The tiles are 14" wide, so the reveal must be about 7" and overlap can be no more than 1 1/2".

 

[Reciprocity]

In the roof picture, the reveals are twice as wide as they are tall. The tiles are 14" wide, so the reveal must be about 7" and overlap can be no more than 1 1/2".

Based on what. Its pretty clear to see only bout 3-4" is exposed. The tiles MUST be over 2x as tall as what is exposed. Its not an optional thing. that's how it works. Every inch of the roof will be covered by 2x material and there is some room for fastening the tile to the roof where there is triple coverage.

If you are talking about the reveal where Elon was showing a tile? I dont get the impression from anything that I saw that the physical tile was 2x as wide as it was tall, though that is not wants important. Whats in important and a fact, not idle speculation, they will need to be over 2x as tall of the EXPOSED tile. I grabbed a screen shot of a banner from this forum:

The circle shows triple coverage where he is nailing and shows how its over 2x as tall as the exposed area, then the shingles are offset by a minimum of 4-5" or about the height of the exposed area:

This is how roofing works. Its not rocket science. This guy is roofing over an old roof, so it takes the place of the job the felt would do as there is felt still under the old roof. Code is different in different places, typically allowed 2 layers before you have to tear off the old roof, and you would not be able to put solar tiles over an existing roof.

 

[brucet999]

Based on what. Its pretty clear to see only bout 3-4" is exposed. The tiles MUST be over 2x as tall as what is exposed. Its not an optional thing. that's how it works. Every inch of the roof will be covered by 2x material and there is some room for fastening the tile to the roof where there is triple coverage.
/QUOTE]
"Reveal" is the term for that part of a shingle or tile that is exposed.

In the picture from the Tesla Solar site - linked here in post #232 - one can clearly see that the width of exposed tile is twice the height. If that reveal were only 3-4" as you say, then the tiles would have to be only 7" wide, but they are in fact 14" wide.