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Deal Addict
Nov 25, 2014
1374 posts
569 upvotes
Newton Brook, ON
ChubChub wrote:
Jul 10th, 2017 8:00 pm
I see what you're saying: Presumably, if you put $100k into a roof, you'd then have $3k extra per year to put into "something", which would logically be a compounding bank account (for argument's sake, we'll say you can put those monthly payments directly into something that pays whatever interest rate we're talking about). Thanks for pointing that out, but your numbers are definitely wrong; you're ignoring the $100k you're not spending on the roof. Coincidentally, my calculations were also incorrect in the opposite direction; I was adding $100k to the solar roof for some reason ... so that $8k in solar's favour should have been $182k - $90k = $92k in saving's favour, however the omission of the monthly deposit interest on the solar side was a mistake anyways, so it's goofed.

Much simpler: how much money do you have in your bank account based on either an initial deposit + compound interest (asphalt roof), or a monthly deposit of your generated power + compounding interest (solar roof).

For this, you'd need to definitely know how much cash you're getting out of the panels; $3k is definitely generous, but we can stick with that. I'll stick with a generous $3.25% interest GIC as well, since we're talking about extremes anyways, and that is actually currently a potential achievable rate (I'm generating these calculations from here: Click Me ). :

...
I'm not ignoring the money spent on the roof, I'm assuming it adds to the resale value. The fact that you're assuming no added value here is part of what makes your comparison one-sided, which was my point. Notice I said: If it increases value by the same amount as the investment and appreciates 2% each year, it already matches a 2% GIC. Sure, if you just look at "what's in the bank" and ignore the property value, the 3% return becomes a 97% loss, but by that logic you might as well say the GIC is a 100% loss while it's locked away for 5-10 years. To make an apples-to-apples comparison, let's say the home is also sold at year 30 or 60.
You need someone with an umbrella not a fork
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Oct 9, 2010
1691 posts
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Windsor
nmclean wrote:
Jul 10th, 2017 9:54 pm
I'm not ignoring the money spent on the roof, I'm assuming it adds to the resale value. The fact that you're assuming no added value here is part of what makes your comparison one-sided, which was my point. Notice I said: If it increases value by the same amount as the investment and appreciates 2% each year, it already matches a 2% GIC. Sure, if you just look at "what's in the bank" and ignore the property value, the 3% return becomes a 97% loss, but by that logic you might as well say the GIC is a 100% loss while it's locked away for 5-10 years. To make an apples-to-apples comparison, let's say the home is also sold at year 30 or 60.
So, you're assuming that $100k into a roof is actually worth $100k when reselling, and it somehow is worth MORE every year? That roof is basically like a pool; there's value to the owner, but adds nearly zero to the resale value of the home (out where I live, it actually depreciates the home). To me, I'd consider a $100k fire liability on my roof being a bad thing (I assume my insurance company would too), even if it theoretically generates power. As well, solar panels get cheaper and more efficient every year (who knows where it will plateau), not 2% more expensive.

If you're considering the roof to actually have value anywhere near its cost to purchase and install (which is an ENORMOUS assumption ... I'd say, at BEST, you're looking at $40k in value added to the home day 1 ... and that's being VERY generous), you'd then have to assume depreciation on that (not appreciation; I'd love to know how you think that's possible, even in a fantasy world, that technology that wears out, and is worse than current products, somehow appreciates). At 60 years, the roof is DEFINITELY adding zero to the resale value (earlier, if Tesla bankrupts the solar panel division before that); the panels will likely have begun failing, and at BEST, they'd be at 50% efficiency for the ones that still work. This means that you'd adjust the initial cost of the roof to $60k ($100k actual cost, but $40 you could theoretically get back = $60), and you'd remove the depreciation of the roof from your monthly deposit ($40k/60years = -$670/year).

I'm sure you'll not think those numbers are valid, so feel free to enter whatever you want into a savings calculator. Payoff time will still be at least 30 years, even if you want to ignore most realities of life.

Also, at 2%, we're not talking GICs; that's a generic savings account. 3.25% would be GICs, and yes, you're right that it's "locked away" for 5 years ... but in that scenario, the Tesla roof NEVER pays itself off. As well, it's not like your cash is not available for 5 years, you just lose 1-5 years of interest if you need it for some reason. Thats why I had to give an extremely unlikely scenario (best for solar, worst for savings) to make it even theoretically pay off, for a 30 year old, when they turn 80 years old.
One who is offended by truth, has no place among those who seek wisdom.
Deal Addict
Nov 25, 2014
1374 posts
569 upvotes
Newton Brook, ON
@ChubChub I think we're going off the rails. We agreed in the first place that both the 3% from power savings and 3.25% from GIC are unlikely extremes. I was simply showing you that your calculations were incomplete because they ignored most of the variables. The first variable was given by @Cas77 as ROI = 3%, which by definition means we are assuming no depreciation (103K value and 100K cost). We both incorporated that assumption into our calculations, with the caveat that it probably wouldn't reflect the real world. You don't need to argue something I already know.

As for the real world, I recall reading analyses that solar panels actually do add significant value, but I'll leave that discussion to people who are more knowledgeable on that. In any case, one thing you still seem to be forgetting is that products and services are affected by inflation, unlike cash. So even if something loses 60% of its value, it will generally still be worth more than 40% of its initial dollar value - so once again, you're doing an apples-to-oranges comparison there. By the same token, the cost of electricity will increase, adding an additional layer to the power savings return.

BTW, Oaken's 3.25% GIC is not cashable, so yes, it is "locked away". Winking Face
You need someone with an umbrella not a fork
Newbie
Jul 7, 2017
58 posts
10 upvotes
I'm looking into solar but not the Tesla roof. My house is heat pump (no back up) and at nearly 13 cents / KwH (I think that's the unit) for Tier 2 in B.C., it is an incentive. The previous government wants to increase power rates ~50% over 7 years to pay for a new mega dam and balance provincial coffers.

As for rate of return, one has to remember that GIC and other investment earnings are pre-tax while solar savings are after tax.

As far a costs, yes, they're gong down rapidly but the biggest cost in our part of the world is labour and that's not going down. Installation (en masse) is more viable in India with cheap labour.

My local solar installer posted this:

link about roof tile solar not being a good idea.
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Mar 23, 2008
4977 posts
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Edmonton
thriftshopper wrote:
Jul 16th, 2017 8:22 pm
I'm looking into solar but not the Tesla roof. My house is heat pump (no back up) and at nearly 13 cents / KwH (I think that's the unit) for Tier 2 in B.C., it is an incentive. The previous government wants to increase power rates ~50% over 7 years to pay for a new mega dam and balance provincial coffers.

As for rate of return, one has to remember that GIC and other investment earnings are pre-tax while solar savings are after tax.

As far a costs, yes, they're gong down rapidly but the biggest cost in our part of the world is labour and that's not going down. Installation (en masse) is more viable in India with cheap labour.

My local solar installer posted this:

link about roof tile solar not being a good idea.
So your local solar installer (who has everything to gain by the Tesla roof tiles failing) thinks the Tesla system is not a good idea... Even before he's seen them.

Got it.

C
Newbie
Jul 7, 2017
58 posts
10 upvotes
The installer didn't write the article. Someone else did. Lots of valid concerns. Looks like it's been tried several times.

If Tesla finds a way to do with without the catastrophic failures, and at a commercially-competitive price, good for them.
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Mar 23, 2008
4977 posts
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Edmonton
thriftshopper wrote:
Jul 19th, 2017 2:32 pm
The installer didn't write the article. Someone else did. Lots of valid concerns. Looks like it's been tried several times.

If Tesla finds a way to do with without the catastrophic failures, and at a commercially-competitive price, good for them.
I would hazard a guess that most industries have had significant failure rates for the first companies that tried them. Innovating and developing good products is hard. And expensive. And risky. But if I had to bet money on someone who could make a go of something like this, Elon Musk would probably be a good horse to bet on.

C
Newbie
Jul 7, 2017
58 posts
10 upvotes
The avoidable fact (a matter of physics?) or constant seems to be that functioning solar panels generate a lot of heat. If Tesla finds a way to generate power w/o heat or a 100% reliable way to dissipate the heat reliably, then it's a go. I don't know the technical challenge myself but the Tesla roof - even if available - is moot for me as my new house has ~13 year old concrete tiles so it won;t be an economically efficient way to install.
Banned
Jun 19, 2017
256 posts
180 upvotes
Seems pretty shitty considering most people move every few years...
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Jan 6, 2011
3193 posts
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GTA
Cas77 wrote:
Jun 9th, 2017 9:16 am
Find me another investment guaranteed to bring me 3%...I'm all ears.
Google Honda MCHP or FreeWatt, ROI~20%

When solar roof ~10% ROI then we are talking.
Deal Guru
Aug 2, 2001
14175 posts
4635 upvotes
LongLiveRFD wrote:
Oct 4th, 2017 9:41 pm
Google Honda MCHP or FreeWatt, ROI~20%

When solar roof ~10% ROI then we are talking.
Can you explain more about this? It seems interesting but I can only seem to find news articles about it and nothing more.
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Jan 6, 2011
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TrevorK wrote:
Oct 4th, 2017 10:18 pm
Can you explain more about this? It seems interesting but I can only seem to find news articles about it and nothing more.
Try Youtube as well.

Basically harvesting heat off nat gas atkinson engine which generates power.

That means, free hydro in winter (because high heat demand) and free heat in summer for domestic hot water (because high hydro demand).

Or, you can crack it up to your hydro demand only, then you earn spark spread between time-of-day and gas fuel.

If you lever its ROI say 5:1 or 20:1, your IRR should approach 40-50%. And your house is essentiall off-grid and hybrid power.

Oh, and our govt pays you rebates using other taxpayers money for it too.

Edit: Problem with Tesla's current implementation, the panels do not harvest heat otherwise it's cogeneration onsite, which makes you off-grid.
Deal Guru
Aug 2, 2001
14175 posts
4635 upvotes
LongLiveRFD wrote:
Oct 4th, 2017 10:33 pm
Try Youtube as well.

Basically harvesting heat off nat gas atkinson engine which generates power.

That means, free hydro in winter (because high heat demand) and free heat in summer for domestic hot water (because high hydro demand).

Or, you can crack it up to your hydro demand only, then you earn spark spread between time-of-day and gas fuel.

If you lever its ROI say 5:1 or 20:1, your IRR should approach 40-50%. And your house is essentiall off-grid and hybrid power.

Oh, and our govt pays you rebates using other taxpayers money for it too.

Edit: Problem with Tesla's current implementation, the panels do not harvest heat otherwise it's cogeneration onsite, which makes you off-grid.
I'm having a hard time finding out why it's not more popular. It seems the startup cost might be high (sites are saying $12K-$15K, but no idea if thats USD or CAD). Which doesn't seem outrageous. Am I missing something obvious?
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Jan 6, 2011
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TrevorK wrote:
Oct 5th, 2017 9:55 pm
I'm having a hard time finding out why it's not more popular. It seems the startup cost might be high (sites are saying $12K-$15K, but no idea if thats USD or CAD). Which doesn't seem outrageous. Am I missing something obvious?
Could be social attitude or resource abundance. The North Europeans have done this for decades, and at community or block level (underground heat pipe and locally generated hydro). Only the private/public/commercial interests from the common wealth countries caught on, not residential. $15K must have been USD, because Canadian consumers are on perpetual lag behind US in terms of pricing and quality.

Watch this and how Germans consider mCHP as hyper efficient "boilers":


And Stirling engine is still mechanical. Once natgas/hydrogen fuel cell (where certain Canadian firms are global leaders) got cheap, the efficiency of Tri-Gen (heat/cool/power) approaches new theoretical limit, the stronger hydrogen and oxygen bonding vs weak fossil fuel burning chemical bonds.

Also consider the following facts:
1. With heat, you can "generate" cooling, via equipment such as evaporator/condenser. In other words, you can burn gas to cool spaces. Low Carbon strategy.
2. By feeding recycled organics/sweage into digesters, methane can be harvested instead of flaring into atmosphere. Only 3rd world caught on, on-site bio gas generation. In other words, poo-powered home. . Carbon Neutral.
3. With solar, highest RIO is solar heating, the hydro may be considered a by-product/free gift. Carbon Free.

Musk stated Mars in 6yrs and Telsa has only opened a small crack using photovoltaic for limited indoor lighting.

Yet, we couldn't get shit together on earth and wasting shit tons of energy. We don't harvest winter sun's thermal energy to preheat air or domestic water, we burn nat gas to heat space and not get the free hydro out of it. And we dump our organic matters into the plants/landfills and let methane to destroy the climate.

Solar roof is too expensive for the little it does to energy security and the environment.
Deal Guru
Aug 2, 2001
14175 posts
4635 upvotes
Thank you for your posts and all the links - they have been very informative. I'm going to look into this concept further because within 5 years I need to replace my furnace anyways.

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