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

[NW-Bound]

When I installed solar on my Phoenix home in 2012, rather than a zero electric bill, I was more interested in the best bang for the buck. At that time, this meant offsetting most (preferably all) summer peak hours usage using the net metering in use at the time while minimizing the end of year excess kWhs in your account that were paid off in peanuts ~$0.03 per kwh. In the seven years that I owned the home, this worked well as all my peak usage (@$0.25/kWh) was eliminated and so was much of the lower cost usage. I ran spreadsheets that showed I was saving about $1500 (out of an annual electric cost of about $2200 per year prior to solar) with a 6.9 kW Sunpower system...

Ah, I live in Phoenix, so can relate to your situation. And my DIY system is somewhat comparable to yours.

I had 7.6 kW worth of solar panels, but their production is less than ideal due to shading from the neighbors trees (2/3 of the panels are ground-mounted). The array is being upgraded to 10 kW.

Being an off-grid DIY system, mine is not grid-tied. The net metering policy has also been discontinued except for grand-fathered systems. The same is happening in many other states such as California.

Hence, I built a lithium bank from start to store the excess power for use when the sun goes down. My battery is 32 kWh, or rather was, as it is getting worn out in its 4th summer. When it gets cooler, I will add another 12 kWh.

In spring and fall, the array can generate enough for daily use, with the surplus going into the battery for use until the sun rise the next day. This means I could be totally off-grid.

Currently in the summer, the battery does not get fully charged because the daytime consumption is high. I run out of battery juice at about 10PM, and the autotransfer switches cut back to the grid. This still helps reduce the bill, because the on-peak period ends at 8PM. The rate drops from 25c/kWh to 8c or so.

Extending the run time past the 8PM peak-period cutoff gives me only 8c instead of 25c, so the marginal benefit is not as high. However, I worry about the future, when the utilities may institute rolling blackouts due to demand exceeding supply. Both SRP and APS have sounded the alarm about this.

 

[Texas Proud]

I do not see how you can ignore opportunity costs when buying something as expensive as this...



First, it is not a car, house or 12 pack of coke... the need for the first two require a different calculation... but implicit in those decisions is opportunity costs... who cares about the coke...


I will round to $100K... that would give me at minimum today $5,000 per year income... since I spend about $1,000 a year on electricity it makes zero sense to spend that kind of money... Heck, even a $20K system is suspect..


For me it is irrelevant as my roof is pitched to steep in a lot of places and all of it is shaded most of the day... a neighbor down the street put in I think an 8 panel system and then a few months later cut down two big trees in their front yard.... not a smart move...

 

[NW-Bound]

I do not see how you can ignore opportunity costs when buying something as expensive as this...

Opportunity cost is no longer a major concern where:

1) you make money off YouTube videos. This applies to many YouTubers whose channels are about solar and lithium battery storage.

2) it's a hobby. People spend big money on planes, boats, fancy cars and don't care about costs.

3) one tries to get some insulation from potential blackouts due to the fragile local grid.

In my case, it's 2) and 3). I have not spent anywhere near $100K though.

 

[Fermion]

I totally get doing solar as a hobby. We spent a lot of money turning our sailboat into an electric drive and it makes zero financial sense but was still a fun project and also fun to be whisper quiet.

Spending 100k to save even 3k a year would make no sense though when as pointed out you can get $5k from that in a treasury bond.

 

[Texas Proud]

Opportunity cost is no longer a major concern where:

1) you make money off YouTube videos. This applies to many YouTubers whose channels are about solar and lithium battery storage.

2) it's a hobby. People spend big money on planes, boats, fancy cars and don't care about costs.

3) one tries to get some insulation from potential blackouts due to the fragile local grid.

In my case, it's 2) and 3). I have not spent anywhere near $100K though.

Yep... I can agree with you with a but...


1) Opportunity costs are more than covered by the income you are getting...


2) (and this is just for fun)... the opportunity costs are you cannot spend that money on some other hobby (well, unless you are really rich I guess)


3) Totally agree... but I bought a whole house generator for just over $10K... and I might say it was well worth the money.... and not nearly near $100K...


Also as mentioned... I would not have a payback period with his system as I do not have that high of a bill right now... but it is about to go up 25% or so as my contract expired yesterday...

 

[NW-Bound]

...I bought a whole house generator for just over $10K... and I might say it was well worth the money.... and not nearly near $100K...

For me, I don't have NG service to get a fuel source for a whole house generator, and as people find out, generators gobble up a lot more fuel than one can stockpile to safeguard against power outages of longer than just a few hours.

Hence, I count on my solar+battery system to help me survive. I have a small 2-kW portable inverter generator to supplement the solar power if necessary. If running flat-out, the small generator can produce 43 kWh/day, and that is way more than needed, as we never have a day here in Phoenix when a solar system does not produce power. Even with the rare cloudiness, the diffused sunlight still gives me 1/3 of the normal solar production.

The large battery storage serves as a reservoir, so that I will not have to run the generator constantly to charge it (to supplement the solar panels). It is also a big buffer, so that I can have instantaneous usage of higher than the 1.8 kW output of the generator. Same as it does now to buffer the panel outputs.

If it comes to this, I may still have problems rounding up the tens of gallons of gasoline to feed the generator.

People are already talking about what would happen here if we have widespread power outage. A lot of people will die from the heat. It may seem farfetched, as we have not had rolling blackouts like in California last year. Any power loss has been small and localized to a small neighborhood due to a distribution transformer or a power pole being down. Nothing systematic.

But then, I remember that before Katrina hit New Orleans, there was a study talking about the effect of a Cat 5 hurricane, and people did not care to pay attention. Nah, it can't happen, they said.

 

[ERD50]

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

 

[NW-Bound]

I am usually curious about how the public views these videos, so scroll through the comments to see what people think. Quite a few did raise the same questions, but most just oohh'ed and aahh'ed over his system.

A solar system of 29 kW rated output would cover a roof area of 1,500 sq.ft. using conventional PV panels, so that is really impressive. This being built with solar tiles would cost a lot more than what he paid, given the price that other people paid for a much smaller system. There are all kinds of head-scratching details like that. Still, the laymen would not know such thing.

Again, most people don't know the difference between kW and kWh. This YouTuber did. I always cringe when I heard some other YouTubers say "kW per hour". ARGHHH !!!


PS. I don't subscribe to his channel. I don't subscribe to any channel actually, but there are YouTubers I revisit every so often, if I remember.

 

[Zathras]

The only thing I can think of, to help explain the power usage, is if he runs his own server farm out of his house.

 

[ERD50]

The only thing I can think of, to help explain the power usage, is if he runs his own server farm out of his house.

That was mentioned in some comments - but then, he also mentioned gas heat - would he even need heat with a server farm like that? Hmmm, we can make some estimates:

I already generously discounted his EV as using 10 MW-hr, leaving 44 MW-Hr, which is 4 to 5 x the average for NJ, where he lives. Let's assume his home is 2x the average, so that leaves 22MW-hr average 'excess'. That's a continuous 2.5 kW (actually MORE excess in winter, he's not running his A/C, which would be the largest most likely)...

Well, that 2500 watts is 8530 BTU, but a furnace is maybe running 1/3rd the time over much of the winter, so that's like a 25,000 BTU furnace - small, a larger SFH would be more like 100,000 BTU.

But again, if much of that bill is toward A/C, then there'd be much more excess in the winter, so a server farm like that could provide a significant % of his heat.

But I've read that mining isn't profitable anymore w/o ASICs and cheap electricity, and his $0.17 is above average, not cheap at all, so I doubt he's mining. Can't imagine what he'd be doing with any other sort of server farm.

-ERD50

 

[Martlet]

I only watched a few seconds of the video -- clearly an outlier in almost every respect -- system capacity, configuration and cost.
The attractiveness of roof-mounted residential solar does depend on local rules for net metering and on available incentives. Here in my part of Massachusetts (Eversource East utility) it's a no-brainer win for most houses. Net metering is at the full distribution plus generation tariff, less a small distributed solar item (about $0.015 per kWh). There's a state tax credit in additional to the federal credit. And there's a state renewable energy incentive that pays out at about 9c per kWh generated (whether used behind the meter or exported). The fixed charge from Eversource is $10/month. I estimate that our system, installed in 2020 will have a payback time around six years. The cash incentive goes away after ten years and I expect that net metering will gradually move to either just the generation charge as a credit or to some wholesale electricity price as a credit.

Just as a calibration of the system in the video, we installed a ~12 kW DC system that produces 16 -17 MW-hr annually. Our usage is somewhat lower, around 15MW-hr, and this has resulted in a net metering credit balance above $2k that we'll eventually use if we switch to cold climate heat pumps and/or electric vehicles.

 

[JJpop]

I only watched a few seconds of the video -- clearly an outlier in almost every respect -- system capacity, configuration and cost.
The attractiveness of roof-mounted residential solar does depend on local rules for net metering and on available incentives. Here in my part of Massachusetts (Eversource East utility) it's a no-brainer win for most houses. Net metering is at the full distribution plus generation tariff, less a small distributed solar item (about $0.015 per kWh). There's a state tax credit in additional to the federal credit. And there's a state renewable energy incentive that pays out at about 9c per kWh generated (whether used behind the meter or exported). The fixed charge from Eversource is $10/month. I estimate that our system, installed in 2020 will have a payback time around six years. The cash incentive goes away after ten years and I expect that net metering will gradually move to either just the generation charge as a credit or to some wholesale electricity price as a credit.

Just as a calibration of the system in the video, we installed a ~12 kW DC system that produces 16 -17 MW-hr annually. Our usage is somewhat lower, around 15MW-hr, and this has resulted in a net metering credit balance above $2k that we'll eventually use if we switch to cold climate heat pumps and/or electric vehicles.

I really do not understand why anyone would pay Tesla so much money when there are so many great options at a fraction of the cost.
Ego?
Status?

 

[GaryInCO]

I'm a long-time Tesla fan (though a lot less lately) and I drive a Tesla. I wouldn't buy the Tesla roof tiles because they're way expensive, and Tesla has been a bit flaky in selling and supporting them.

I have a stupid-large but relatively efficient house. I have gas heat (avg 170 therms/month Nov-Apr), and my electric use averages 1000 kWh / month. I'm in the process of figuring out how much power would be required to run a heat pump to replace the gas heat.

A solar system to replace my 1000 kWh/mo usage runs somewhere in the $25k-$30k range (after IRA credit). I haven't gotten a good answer for how much it will take to replace the gas heat, but the solar estimators are wet-fingering it at about 20%. It makes financial sense because the monthly payment on a 12yr loan for the system is roughly the same as my current utility bills. So I freeze my utility costs at roughly the current cost, I'm protected from future rate increases (and my gas/elec bills DOUBLED in the last 5 years), and in 12 years my "utility bill" drops to zero. And I feel good about reducing my fossil fuel consumption.

It may not look quite as rosy by the time I nail down all the numbers, but I think it makes sense.

 

[NW-Bound]

Solar panels are getting dirt cheap. Used ones, particularly the lower-efficiency polycrystalline are going for $25 per 230W panel. The shipping cost is high, so if you can get them locally, they are great.

On YouTube, there are guys showing these used panels putting out 90+% of their rated output. So, what's going on?

Many of these come from commercial solar farms, and it was said that they pulled them out to replace with new higher-efficiency monocrystalline panels. This upgrade makes sense, as they get more power with minimal upgrading of the rest of the system. The panels may have been depreciated to nothing, so just toss them.

I cannot use these because my installation space is limited, and I have to use the monocrystalline ones which cost more. But I told my wife, if I lived in the countryside and have a big lot, just lay them out on the ground and connect them with a bit of wires, and get power out the wazoo.

Of course, if you are in tornado country, it's not so simple. YMMV, to borrow from Koolau.

PS. By the way, the common size is roughly 64"x40". Poly panels put out about 230W, while mono panels put out 330W.

 

[catii]

We installed solar all the way back in 2010, & are still very-happy with it. DW & I are both (now retired) engineers, so running the numbers wasn't difficult, & we live where the cost of power is phenomenally high! Back then, it was "only" $.33/kWh, now peak is at $.69/kWh! Our "green loan" was less than our monthly electrical bill, from day one.

Installed 10.5 kW of solar PV panels, with an after-tax-credit cost of $48K.That was offset by our average monthly electric bill of about $380. That would have given us a break-even of about 10.5 years, but the price of power kept rising, & the system was "paid off" in 7 years.

I keep a spreadsheet that shows generated power for every day, & of course I expected a slight downward trend due to lower panel efficiency over the years. But around year 7, it dropped off rapidly, which didn't make sense. The first action I took turned out to be all that was needed - I hired a company to thoroughly clean my 42 panels. That jumped the power generation back up to about what was generated back at year 3! My advice is to get your panels cleaned professionally every 3 years. Trust me that just hosing them off isn't the way to go.

We've considered installing a battery backup system, but haven't yet taken that plunge. Why? Well, we both used to work in the energy field (U.S. Dept. of Energy), & I couldn't find battery technology that met my criteria for safety, reliability, & durability. I've seen dozens of lithium-ion batteries fail for no apparent reason, & burn down the structure - no thanks! Firefighters try to douse the flames with water, which is dumb! Go & google what happens when you add water to lithium!

Sodium-ion batteries are safer, but wear out faster. Lithium-sulfur batteries are also safer, but don't have the capacity. I like Zinc-Manganese Oxide batteries, but again not enough capacity. At the moment, Lithium-Iron-Phosphate (LiFePO4) batteries have my vote, & I'm waiting for the price to drop. The main disadvantage is the scarcity of lithium. Right now, I just have two small generators to run our two refrigerators & two freezers in the event of a long-term power outage. They run on gasoline or LNG, but ask me again, in a few years, because I may have decided on batteries by then. There are also some interesting new power inverters that act as a backup battery system when the sun shines, & I'm keeping an eye on Enphase.

Yes, solar PV is definitely the way to go, & we also have solar hot water. Our monthly electrical bill is $18, which is just the connect charge. We're on net metering, which allows our generated power to offset what we actually use, & "banking" the excess for the two or three winter months, when we don't generate enough power from solar. We're listed as "net power generators" because we produce far more power than we use each year, which Hawaiian Electric gets for free.

 

[boont]

Solar

I am planning to install solar at my country house in the California wine country. I don't want PG&E to even know I have it and I don't want any of their rebates or costs to attach to their system.

I have PG&E at this house and will continue to stay connected but I know they will be raising rates from here on out so no thanks to those fake give-back discounts.

I will run my heat pumps off solar for air-conditioning or winter heat. That's enough for me. I also have enough oak firewood from the property to last a life time.

 

[Zathras]

That was mentioned in some comments - but then, he also mentioned gas heat - would he even need heat with a server farm like that? Hmmm, we can make some estimates:…
-ERD50

Yeah, that is a lot of power. I wasn’t thinking of Bitcoin Mining though, just business related servers. Now, I don’t know he is hosting his own websites, media server, mail server, streaming server, etc. But that is a possible draw.
For all I know he has an Olympic sized pool heated with electricity.

It would be nice to see why he uses so much electricity.

 

[NW-Bound]

...around year 7, it dropped off rapidly, which didn't make sense. The first action I took turned out to be all that was needed - I hired a company to thoroughly clean my 42 panels. That jumped the power generation back up to about what was generated back at year 3! My advice is to get your panels cleaned professionally every 3 years. Trust me that just hosing them off isn't the way to go...

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?

... At the moment, Lithium-Iron-Phosphate (LiFePO4) batteries have my vote, & I'm waiting for the price to drop...

There are several LFP battery packages on the market, all going for less than $1500 for 5 kWh. They are all from China (the only maker of LFP cells as I know), but the higher priced ones even have a UL listing. Still, I want them away from the living space, and in my garden shed.

 

[NW-Bound]

Yeah, that is a lot of power. I wasn’t thinking of Bitcoin Mining though, just business related servers. Now, I don’t know he is hosting his own websites, media server, mail server, streaming server, etc. But that is a possible draw.
For all I know he has an Olympic sized pool heated with electricity.

It would be nice to see why he uses so much electricity.

He's a smart guy. He wanted to keep us waiting with bated breath.

 

[anothercog]

I got a solar system about 18 months ago. Financed with a 1.5%, 20 year loan. Based on payments, usage and absurd PG&E electricity rates, my beak even was 8.5 years.

However PG&E drastically raised rates since then and my break even is now closer to 5 years.

But the net metering program changed for the worst earlier this year so the math will definitely take longer now. I’m grandfathered in for the next 20 years. After that, it may not make sense to keep them depending on how efficient they remain.

If you live in a state with cheap electricity and no net metering it likely would not make financial sense.

 

[zippy2020]

...People are already talking about what would happen here if we have widespread power outage. A lot of people will die from the heat. It may seem farfetched, as we have not had rolling blackouts like in California last year. Any power loss has been small and localized to a small neighborhood due to a distribution transformer or a power pole being down. Nothing systematic.

Not sure where you got your info, but CA had no rolling blackouts in 2022. We did have them in some areas in 2020, but on average an RB lasted about 1 hour.

Just want to keep the record straight, that's all.

 

[2017ish]

Didn't watch the video (I don't believe in watching internet videos without compelling reason!)

Son just got 18 Solar panels and a couple of batteries/Powerbank via Tesla. North of 40K. He calculates that they'll make it back in 6-7 years (just barely got into the CA program for selling back to PGE at retail).

More importantly, this is for their weekend/vacation home in Pine Mountain Lakes (near Yosemite). Blackouts are common in the summer, and they have 3 kids under the age of 2. Thus, "worth it" encompasses more than a pure monetary payback.

Given their income, this was a no brainer--even when adding in a new roof that had to be bought earlier than expected.

 

[NW-Bound]

Not sure where you got your info, but CA had no rolling blackouts in 2022. We did have them in some areas in 2020, but on average an RB lasted about 1 hour.

Just want to keep the record straight, that's all.

Perhaps I used the wrong terminology. Rolling blackouts imply power turning off due to insufficient supply.

On the other hand, there might be power loss due to equipment failures or weather factors. This is of course a difference cause, and the fix is different than bringing on more supply.

So, I stand corrected.

From the Web:

• In 2022, California accounted for 24% of all U.S. power outages, and Texas accounted for 14%.
• California, Texas, and Pennsylvania are the states most affected by power outages during the winter.

 

[anothercog]

Perhaps I used the wrong terminology. Rolling blackouts imply power turning off due to insufficient supply.

On the other hand, there might be power loss due to equipment failures or weather factors. This is of course a difference cause, and the fix is different than bringing on more supply.

So, I stand corrected.

From the Web:

• In 2022, California accounted for 24% of all U.S. power outages, and Texas accounted for 14%.
• California, Texas, and Pennsylvania are the states most affected by power outages during the winter.

At least last year there were many reports of power being turned off in fire prone areas with above ground lines during particularly hot, windy days.

We have had a cool summer where I live but last year I did get a few notifications about potential rolling blackouts but my street with underground lines was not impacted while other parts of my town were.

 

[JoeWras]

Of course, if you are in tornado country, it's not so simple. YMMV, to borrow from Koolau.

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.