Tesla Solar (Residential) Roof: Was It Worth It?

[Zathras]

In my mind's eye, I'm imagining these things taking off like an airfoil and becoming part of the swirling debris cloud.

I also kind of wonder about that with roof mounted panels. I've seen a lot go up around here with significant stand-off from the roof. We haven't had a hurricane in a few decades. Wonder what will happen to them. We'll see.

Panels tend to be stronger than roofs in stormy weather.
There was a community in Florida that uses a lot of solar panels. When the hurricane devastated the areas all around them, their panels held strong and gave them power when the regions around them were without.

https://www.upi.com/Top_News/US/202...ar-power-Florida-Babcock-Ranch/5921667486567/

 

[NW-Bound]

^^^ Very interesting. Perhaps modern construction standards make a world of difference.

 

[JoeWras]

Sounds like they have construction standards. That's good!

Hope they are good around here

 

[NW-Bound]

Earlier, I mentioned the recent availability of rack-mounted LFP batteries. It looks like the industry settled on a standard form factor of 19" rack cabinets, each holding 16 LFP cells for a nominal voltage of 48V and a total capacity of 5 kWh. Price is around $1500. Weight is around 100 lbs. Some are UL-listed.

With CA requiring new homes to have solar panels, and with more people opting to have their own residential backups for protection against blackouts, I expect to see a proliferation of the above ready-to-go battery packages.

This is of course good for the consumers. Too bad that there are no US makers of these cells. I am not aware of any LFP cell makers outside of China.

A typical LFP rack-mounted battery looks like the following.

 

[NW-Bound]

This rack holds 50 kWh. That's more capacity than what I have right now (32 kWh, to be upgraded to 44 kWh).

 

[athena53]

I'd be curious how resale value is on a home that has the Tesla power wall and Tesla roof installed...not enough data yet I'm sure but it's something to think about. You'd want to consider the additional cost and if that would be a selling point (and worthy of a higher selling price) or if it would be a negative for some people.

That's been the roadblock for me. I'm seeing estimates of $40-$50K for most homes. Whether I write them a check up front or take out a loan (which, in theory, can be repaid through savings on my electric bill), when the house is sold the loan will have to be refinanced in the new owner's name if I borrowed the cost. If I paid it in full, I might or might not recover the full cost in the sale price. I'm guessing it would be a plus to have a house with a fully paid solar panel installation, but not a plus worth what I paid.

ETA: Just checked my expense spreadsheets. I paid $755 to the electric company the last 12 months. (I live in the midwest and keep my house temperature at 80 in the summer.) Not much potential savings there.

 

[NW-Bound]

This Texan builds his own battery. Each of his cabinets holds 14 kWh.

And he built 16 cabinets, for a total of 224 kWh. He's not fooling around. He also built a dedicated solar shed of perhaps 400 sq.ft to house the solar equipment.

 

[NW-Bound]

ETA: Just checked my expense spreadsheets. I paid $755 to the electric company the last 12 months. (I live in the midwest and keep my house temperature at 80 in the summer.) Not much potential savings there.

How about your heating bills? If it is too cloudy where you are in the winter, solar energy won't help you either with heating.

PS. On YouTube, I saw a few people in the boondocks with a substantial solar system. The arrays are all ground-mounted, because they have beaucoup land. After a winter or two, they cried murder on snowy days. No matter how big the array, it does not do them any good when covered with snow.

One YouTuber looks to get grid-tied. The other is investigating diesel generators. He even got a military-surplus one.

 

[Qs Laptop]

I'm curious if this guy is ever going to do an update, and answer all the questions about his extreme consumption, and how there doesn't seem to be any way his EV could account for much of it.



So many commenters seem to think this guy is such a great presenter, there really should be an explanation for such outlier data.



I'm not going to subscribe to his channel, so maybe someone here can let us know if he ever addresses this. TIA.



-ERD50

Is this relevant?

https://twitter.com/x/status/1692908222611374542

 

[NW-Bound]

Is this relevant?

https://twitter.com/x/status/1692908222611374542

Thanks for sharing.

Heh heh heh... When I first saw the YouTube video, I immediately thought something was badly amiss. It will escape non-solar owners, but because I built, maintained, and measured my own DIY system with storage, I immediately spotted the improbably high solar production of his system.

See my post #16 up the thread. Mystery solved. You cannot defy mathematics and the laws of physics. Heh heh heh...

 

[ERD50]

Is this relevant?

https://twitter.com/x/status/1692908222611374542

Thanks, but no, that is not relevant to the lack of explanation for his high consumption (4~5x the average home in his area, even after subtracting a very generous allowance for an EV). He really needs to explain how it is he uses so much energy (he hand-waved the EV as a contributor, which a lot of people blindly accepted, but that doesn't explain it).

It *is* relevant to the question NW-Bound had about the production numbers (and I now see NW-Bound responded).

edit/add: I see he's getting those questions on Twitter as well. Again, Europeans painting us Americans as energy hogs based on this (no - he's using many times the average American!).

Also odd that Tesla could have such a major 'bug' slip through. I mean, it doesn't seem like he was off in some weird corner of that app, he was just looking at production numbers - it should have been obvious to Tesla those numbers are wrong (NW-Bound caught it right away, I missed it as I was focused on the consumption numbers at the time). What kind of QC is that?

Thanks - ERD50

 

[NW-Bound]

They miscounted the consumption too. From the guy's Twitt:

So it appears Tesla found a bug in their app after watching my solar video that accidentally counted all production and usage totals as DOUBLE their actual numbers.

It sounded like the instrumentation provided by Tesla is all messed up.

The only thing that's reliable, I think, is whatever the utility company measures. They can't afford to mess things up as badly as that.

 

[ERD50]

They miscounted the consumption too. From the guy's Twitt:



It sounded like the instrumentation provided by Tesla is all messed up.

The only thing that's reliable, I think, is whatever the utility company measures. They can't afford to mess things up as badly as that.

But his annual 54,380 Kwh consumption is from his past year's bills (20 minutes into the video), nothing provided by Tesla. Coming up with a $ figure was harder, he has different billing rates over times/season, but the consumption is plain old Kwh.

-ERD50

 

[NW-Bound]

I just watched the video again at that 20-min mark.

He said that the 54MWh was the trailing 12-month consumption, which was after he already had his Tesla solar system installed. And he said "it would have cost about $9660".

So, he never used 54 MWh from the grid prior to having the solar system. That number was what the Tesla system told him that he used with the new system, grid and solar combined.

Yes, dividing the numbers by 2, his 27 MWh/year is still high, but not as far off.

 

[ERD50]

I just watched the video again at that 20-min mark.

He said that the 54MWh was the trailing 12-month consumption, which was after he already had his Tesla solar system installed. And he said "it would have cost about $9660".

So, he never used 54 MWh from the grid prior to having the solar system. That number was what the Tesla system told him that he used with the new system, grid and solar combined.

Yes, dividing the numbers by 2, his 27 MWh/year is still high, but not as far off.

Are you sure? He's looking at his bills, and estimating usage w/o solar - I think he went back to the year before he had solar?

Wouldn't he know if he was paying $9,600 a year, or half that? A 2:1 difference ought to stand out. He did question the Tesla production numbers though, but not his consumption (he even said his EV makes up some of that).

Just seems really sloppy on his part, yet 99% of the commenters praise him

I don't see how this doesn't effect his payback time? He made that calculation by dividing the $ spent on the solar system, divided by that calculated bill. So if the bill would be half, his payback period just doubled to 20 years, right? He said he paid (near) $0 for the year - so whether or not the app is showing the right values, that bill is all that matters, right?

-ERD50

 

[NW-Bound]

Are you sure? He's looking at his bills, and estimating usage w/o solar - I think he went back to the year before he had solar?

Wouldn't he know if he was paying $9,600 a year, or half that? A 2:1 difference ought to stand out. He did question the Tesla production numbers though, but not his consumption (he even said his EV makes up some of that).

When he made the video, he had had the solar system for 12 months. And the 54 MWh number was what the Tesla system told him he used in the past year.

I understood that he said because the grid rate varied during the day he was just estimating what it would cost, if that 54 MWh came 100% from the grid.

I don't see how this doesn't effect his payback time?

Me neither. I have to watch his video again, looking for the relevant details.

And to tell you the truth, I am no longer that much interested in this guy's system.

 

[ERD50]

When he made the video, he had had the solar system for 12 months. And the 54 MWh number was what the Tesla system told him he used in the past year.

I understood that he said because the grid rate varied during the day he was just estimating what it would cost, if that 54 MWh came 100% from the grid.

Me neither. I have to watch his video again, looking for the relevant details.

And to tell you the truth, I am no longer that much interested in this guy's system.

Yea, I started to go back to see if I could figure it out, I thought it was from his bills, but I lost interest in a few minutes. This is so poorly presented, it's just not worth any effort. I had skimmed over the 'sales pitch' for his 'Sleep Eight' bed cooling thing that was supposed to cut down on A/C - well, did he give any numbers? And in that section, he said that his EV was the #1 consumer for his house, but again, HE DOESN'T GIVE A NUMBER. Why not just tell us how many kWh his EV used in that 12 months? We can't assume that #1 means more than half, w/o knowing how he breaks it down. His numbers are just a meaningless jumble. But it sure seems that this stretched his payback period to 20 years. I'm through with this guy, and frustrated that such a poor presentation gets so much praise from so many (who all get a vote!).

And, I haven't seen him answer the many questions on his consumption. Rude!

I'm actually sorry I wasted any time on this guy. Subscribe - hah, no way! Block maybe?

edit/add: Couldn't help myself. The "Eight Sleep" bed cooling/heating system he advertises to help reduce your heating/cooling costs (but only in your sleeping room) costs over $2,000! Hmmm, what's the payback on that?

-ERD50

 

[catii]

Very interesting. I will keep this in mind. What was the visible condition of your panels prior to the professional cleaning? Do you know what cleaning agents they used?

Oops! Sorry I missed your question.

My panels are on top of my second floor roof, 42 feet up, with no safe access for a couple in our 70s. The company that did the cleaning showed me the before & after photos, & although I could see the difference, it didn't look that bad. But my panels could sure detect the difference, doubling the output power!

No idea what they used, although they claimed it was biodegradable, & he hauled the solution up there in a flexible tank, enough for 42 panels.

 

[NW-Bound]

Oops! Sorry I missed your question.

My panels are on top of my second floor roof, 42 feet up, with no safe access for a couple in our 70s. The company that did the cleaning showed me the before & after photos, & although I could see the difference, it didn't look that bad. But my panels could sure detect the difference, doubling the output power!

No idea what they used, although they claimed it was biodegradable, & he hauled the solution up there in a flexible tank, enough for 42 panels.

I currently have 20 panels on a ground mount, and 16 on the roof. The ground-mounted panels are easily cleanable with me standing on a stool.

With the frequent dust storms here in the arid climate, I hose down the ground mounted panels often, and take note of the power output before and after cleaning. I usually see about 5% increase. The panels are usually very dusty before I rinse them.

After reading your post, I went out and washed some panels with dish detergent and a broom. I picked up another 5% increase. The additional step helps, but I do not see the big difference as in your case. I proceeded to clean the rest of them. I have not done the roof-mounted panels, and will wait until it gets cooler.

 

[NW-Bound]

I have always been curious how the solar tiles are connected together. Because the tiles are smaller than standard solar panels of 64"x40", there will be more electrical connections, and that will impact labor cost, and if not done right, also reliability.

Here's an article with some photos that show a bit of the connections. This article also mentioned a competing solar shingle product.

See: https://www.cnbc.com/2023/03/30/tes...solar-roof-systems-in-the-us-study-finds.html

Another thing that came to mind is that the trend with PV panels now is to use microinverters that are mounted on the underside of the panels. The solar tiles have to be mounted flush with the roof, hence I don't see having space for electronics.

Solar tiles are aesthetically pleasing, but the design and installation are much harder, in addition to the higher manufacturing cost.

 

[catii]

After reading your post, I went out and washed some panels with dish detergent and a broom. I picked up another 5% increase. The additional step helps, but I do not see the big difference as in your case. I proceeded to clean the rest of them. I have not done the roof-mounted panels, and will wait until it gets cooler.

Remember that my panels were installed in late 2010. Our roof is head-on to our tradewinds, plus nightly showers (that's how we stay green ), so things stay pretty clean. But 13 years is pushing things. I've got a reminder set to have the panels cleaned every 5 years, or whenever I see a big drop in output power. With electricity rates currently at $.66/kWh, there's big payback for keeping things clean! I grew up in Phoenix, where everything was covered in dust, so I understand how keeping panels optimized takes a bit more effort.

 

[Fermion]

Remember that my panels were installed in late 2010. Our roof is head-on to our tradewinds, plus nightly showers (that's how we stay green ), so things stay pretty clean. But 13 years is pushing things. I've got a reminder set to have the panels cleaned every 5 years, or whenever I see a big drop in output power. With electricity rates currently at $.66/kWh, there's big payback for keeping things clean! I grew up in Phoenix, where everything was covered in dust, so I understand how keeping panels optimized takes a bit more effort.

$0.66/kWh

At that rate you could almost make money operating a honda gas generator!

 

[easysurfer]

Enjoyed the video. He is a very good presenter.

A side benefit of his setup too is no need to worry about snow accumulation on his rooftop.

 

[NW-Bound]

$0.66/kWh

At that rate you could almost make money operating a honda gas generator!

Is that so? Gasoline is expensive in Hawaii, at $5/gal.

Lemme check.

one of the most efficient power generators is WEN 56380i Portable Inverter Generator (Amazon link, link opens in the new window), which features 3400 Running Watts, 3800 Starting Watts, and 2.2 gallons (~8.32 l) fuel tank. It can operate 8.5 hours @50% (1700W) of nominal power.

$5/gal * 2.2 gal / 8.5 hrs / 1.7 kW = $0.76/kWh.

Dang!


PS. By the way, the YouTuber said that his summer peak rate was $0.39/kWh. My summer peak rate is $0.25/kWh.

 

[Fermion]

Is that so? Gasoline is expensive in Hawaii, at $5/gal.

Lemme check.


$5/gal * 2.2 gal / 8.5 hrs / 1.7 kW = $0.76/kWh.

Dang!


PS. By the way, the YouTuber said that his summer peak rate was $0.39/kWh. My summer peak rate is $0.25/kWh.

Maybe a diesel generator? They are supposed to be around 40% efficient. At 37kw-h in a gallon of diesel fuel x 0.4 = 14.8kWh. At $5 a gallon diesel that would be $0.34/kwh.