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Rooftop Solar: Too Expensive to Meter

Ernie Moniz, US Department of Energy, and the solar industry proclaim inexpensive dollar-a-watt solar panels. Let’s look at society’s cost for providing energy this way. Society’s cost is the total cash outlay, whether paid by power producers, ratepayers, taxpayers, or investors. Before starting the math, remember power, measured in watts, is the rate of flow of electric energy, measured in watt-hours; energy = power x time.

Average cost for rooftop solar panel generation systems installed in 2016 = $3.17 per watt of power generation capacity, reports EnergySage. Thus a typical rooftop solar system capable of producing 5,000 watts costs 5,000 x $3.17 = $18,350, complete.

That’s for 5 kW of DC power, which must be converted to AC to be useful. The converter efficiency is about 80%, so the system AC power capacity is 4 kW, delivered only during times of peak sunshine.

But night and clouds reduce the 24-hour, 365-day average production to just 15% of peak capacity here in New England. So average power production is 15% x 4 kW, or 600 watts. That’s $18,350 / 600 = ~ $30 per watt of average installed AC power, hardly dollar-a-watt proclamation-worthy.

The solar panels might last 20 years, during which they will generate 20 x 365 x 24 x 600 = 105,120,000 watt-hours = 105,120 kWh of electric energy.

Dividing the cost by the energy produced gives $18,350 / 105,120 kWh = 17 cents per kWh.

But money’s not free; if you took out a 20-year, $18,350 home equity loan at 5% the interest cost would be $12,000. Dividing $12,000 of interest costs by the 105,120 kWh of electricity adds another 11 cents/kWh.

Thus the capital cost is 17 + 11 = 28 cents/kWh for rooftop solar power, ignoring any maintenance costs over the 20 years,

But 28 cents/kWh is expensive! Most homeowners pay under 14 cents/kWh for electricity delivered from their power company. The power company normally buys its electricity for about 5 cents/kWh from nuclear, hydro, and coal power plants — and even cheaper from natural gas turbine plants. As a naked business proposition, producing electricity with rooftop solar panels is uncompetitive. It’s too expensive to meter and sell.

How can rooftop solar power be profitable? The answer is complex. A rats’ nest of federal and state subsidies, laws, and mandates distributes the costs to other taxpayers and other electricity consumers. The capital cost of the installation is defrayed by federal and sometimes state income tax credits. Production tax credits pay the owner a few cents/kWh produced. The power utility is forced to buy all the power produced at the full retail rate of ~14 cents/kWh from rooftop solar panels, rather than the normal 5 cents/kWh from commercial suppliers. Besides selling kilowatt-hours, solar power owners also get one REC (renewable energy credit) for each kWh generated. Many states mandate that x% of utilities’ power generation come from solar. Utilities meet this fiat by buying the RECs, which trade at 20-40 cents/kWh.

TradeSolarRECsMA

Utilities buy both power at about 14 cents/kWh and RECs at 20-40 cents/kWh from rooftop solar generators, who thus have an income stream of 34-54 cents/kWh generated. Utilities recover these high costs by increasing rates charged to all customers.

Much of the federal subsidies are hidden costs, in the form of income tax credits, which are significantly valuable to those in higher tax brackets. Ever see a mobile home with rooftop solar panels? Lawmakers like dolling out largess to their supporters with such tax preferences, because they don’t show up as budget appropriations. However by paying higher electric rates the mobile home owner is subsidizing the owner of the McMansion with the rooftop solar panels.

Problem: Rooftop solar is too expensive to meter. Answer: Don’t run the money through the meter. Run it through tax credits, subsidies, and renewable energy credits.

Robert Hargraves's picture

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Josh Nilsen's picture
Josh Nilsen on Jan 16, 2017 9:19 pm GMT

There is so much wrong with this you should feel ashamed.

Solar costs and market rates differ significantly from region to region. Try focusing your analysis on one specific place.

This is just blatant out of context trolling.

Robert Hargraves's picture
Robert Hargraves on Jan 16, 2017 10:26 pm GMT

The numbers are right. Yes, the markets and subsidies do vary crazily from state to state. Here’s a guide designed for investors.
https://solarpowerrocks.com/vermont/
Select your state from the right-hand column, then look at the specific subsidies!
Rebates, Tax Credits, Performance Payments, Property Tax Exemptions, Sales Tax Exemptions, Renewable Portfolio Standard, RPS Solar Carve-Out, Electricity Prices, Net Metering, Solar Loans, Solar Purchase Power Agreements, ….This is where the money flows.

Engineer- Poet's picture
Engineer- Poet on Jan 17, 2017 3:49 am GMT

This very much needed to be said.

Hops Gegangen's picture
Hops Gegangen on Jan 17, 2017 9:33 am GMT

The practice of putting panels designed for utility scale solar in a southwestern desert onto residential rooftops in cloudy regions is clearly not economical. However, that is the past, not the future. The future is building integrated solar — Tesla’s solar shingles and SunFlare’s flexible solar. This will happen first and foremost in areas of high insolation.

I expect a lot of the peak power will go straight to electric vehicles.

Like it or not, there is going to be a lot of solar power in the future, and some of it will be from buildings. Even without net metering, people and especially businesses will find ways to store power and/or demand shift.

Robert Hargraves's picture
Robert Hargraves on Jan 17, 2017 2:13 pm GMT

“areas of high insolation”? I used 15% solar capacity factor, but even in Hawaii the average capacity factor is under 20%.

Storing solar electric energy is not nearly economic. $200 for a 1 kWh battery that lasts 500 cycles adds 40 cents/kWh.

A good example of economical demand shift technology is solar hot water stored in insulated tanks, very common in China.

Darius Bentvels's picture
Darius Bentvels on Jan 17, 2017 3:09 pm GMT

Robert,
I studied Thorcon and was left behind with some questions. May be you can react. Assuming the data at the Dane Wilson PPT of Okt.5 is still valid:

1. Seems to me that your scheduled production costs of 2.4cnt/KWh (sh.4) offers some opportunity in 2025. However, I see that you estimate AP1000 at 9.4cnt/KWh while it’s clear that the AP1000 costs are more in the range of 12-16cnt/KWh.
Which generate doubt about the underpinning of your 2.4cnt.
If reality shows to be ~4cnt/KWh than you will have little chance in 2025 as then solar & wind will be below that range in most parts of the world.
So how firm is that 2.4cnt?

2. The design has 2 heat exchangers and a steam generator.
– Heat exchangers & steam generators are rather expensive (and notorious for leakages), which don’t fit well with your low price per KWh?
– These heat heat exchanges behind each other also imply that reactor power changes will reach the turbine with substantial delay, which makes the design less suitable for flexible operation. But in 2025 there will be to much base load everywhere as wind & solar penetration will be much higher then and be nearly everywhere.
Which implies there is little market then for new semi-base load.
How do you look at this?

3. You plan to use graphite moderator. But we know from the ORNL experiment that graphite get “poisoned” rather fast?
TAP seems to have a solution for that. Why don’t you go along with them?

4. We also know that the improved Hastelloy-N steel still wears relative fast.
The Chinese hope for a solution by:
– finding a fluoride salt mix which allows to operate the reactor at lower temperatures (less than 650°C); +
– finding a better steel alloy.
Seems they fail with both. What is your solution for it?
Throwing the cans+tubes+pumps away after a few years of operation, like Terrestrial?
Seems to me a pretty expensive solution.
Refurbishment of the cans is also a dark horse with Terrestrial.
So some more light on that would help.

Thanks already for your time.

Torrey Beek's picture
Torrey Beek on Jan 17, 2017 4:23 pm GMT

Hi Robert, interesting and important article. I work in the public sector promoting solar, and while I am grateful for the tapestry of credits, incentives, and programs which support solar, it is likely that remuneration structures will be revised and amended with an eye towards longer-term sustainability.

However by paying higher electric rates the mobile home owner is subsidizing the owner of the McMansion with the rooftop solar panels.

Have you seen any numbers, or have any available, that quantify this? There is indeed a cost shift with rooftop solar in most locations, but I think it’s important to accurately frame the magnitude of the cost shift. Cost shifts at solar less than 5% are noticeable, but not to the point where they threaten the financial situation of ratepayers. Cost shifts under high penetrations, particularly with current rate structures, is a different animal.

To that end, there is interest among many stakeholders to reform rates and ratemaking in general to more accurately reflect the benefits and costs of rooftop solar, as many on this board are aware.

Paul O's picture
Paul O on Jan 17, 2017 4:59 pm GMT

Torrey, for most people who are appalled by the cost shifting, it’s not simply the degree and the actual amounts cost-shifted alone, it is also the deception of not revealing this downside when the benefits of rooftop solar power were/are being touted to the public.

Solar power needs batteries, lots of them, and it needs them to be cheap too. One almost never hear of this fact when solar power is being fronted as cheaper than this or cheaper than that.

The sad truth is that with the exception of some industries, some locales, solar power is just not ready to function as a main power source in spite of how cheap it gets.

Torrey Beek's picture
Torrey Beek on Jan 17, 2017 6:13 pm GMT

Paul, by and large I agree with you. To my mind, it is disingenuous to talk about any source being “main” to meeting demand – look where this has/is getting us with coal and NG lock-in. Moreover, with the incoming administration, such talk is hubristic, in my opinion. Diversity of generation resources is a strategic asset, and I see the promise of that diversity growing in terms of renewable energy technologies, DSM programs, and more integrated ratemaking (and hopefully next-generation nuclear energy technologies).

That said, even with the “renewables, et al.” approach above, one can see the dangers of focusing too strongly on renewables by analyzing various capacity markets around the country. I saw a presentation from the head of ISO-NE last year where he explained that downward pressure exerted on energy markets by renewables is pushing up prices in capacity markets.

Sean OM's picture
Sean OM on Jan 17, 2017 7:01 pm GMT

AES just signed a contract to provide electric to Kauai for a solar plus storage peaker system for 11c/kwh. It represents a 2.9c/kwh price drop over their 2015 contract with solar city for a similar system.
These are typically 20+ year contracts.

The only reason why I mention it is because you can kind of see how fast prices are dropping in both the solar and battery storage markets about 20% in the last year for a complete system. The actual cost for installation is higher on islands because of shipping, labor and having to drill through volcanic rock. They are replacing diesel generators, which is similar to American Somoa which did a similar thing. And in fact, it is replicable to most island countries who typically have unstable grids and high energy prices to begin with.

But even in the Northeast ISO region, the average consumer retail price for electric is around 19c/kwh and the cost of wholesale electric is in the 6c/kwh range. However, a lot of the grid is congested, and it is extremely costly to run new lines, add capacity, and/or build new substations. The more solar and storage they can get on the grid, the cheaper it is for everyone. Right now, your complaint is about RECs and other funding options, but the important thing is to get the markets with developed with improved solutions, because what we were doing is not working which is apparent with the great recession, and the oil crisis of ’73.

Mark Heslep's picture
Mark Heslep on Jan 17, 2017 8:01 pm GMT

However, that is the past, not the future.

Not the near future. The global solar panel PV manufacturing base is some 73 GW/yr, at least. Resources of this size can’t be cannibalized over night.

Mark Heslep's picture
Mark Heslep on Jan 17, 2017 8:27 pm GMT

even in the Northeast ISO region, the average consumer retail price for electric is around 19c/kwh and the cost of wholesale electric is in the 6c/kwh range. However, a lot of the grid is congested, and it is extremely costly to run new lines, add capacity, and/or build new substations.

Yes, highlighting the difference between the cost of supporting the entire grid through to the retail customer and the cost of feeding power to the grid. Residential solar, even with a few hours of storage per the Kauai system, can dispace some fuel usage but not transmission needs, not even during all the peak load hours which continue past sundown.

… The more solar and storage they can get on the grid, the cheaper it is for everyone.

Thus not everyone at all. Behind the meter solar shifts cost to those without.

Robert Hargraves's picture
Robert Hargraves on Jan 18, 2017 2:29 am GMT

Here’s another, independent analysis of the difficulty of powering Hawaii with renewables…
http://euanmearns.com/can-hawaii-go-100-renewable/#more-16434

Robert Hargraves's picture
Robert Hargraves on Jan 18, 2017 2:40 am GMT

A few short answers; this really isn’t the place to discuss ThorCon.
1. I calculated AP1000 in George as $16 billion, 2.2 GW, 90% capacity factor, 40 years, 8% interest. Guessed 0.7 cents/kWh fuel plus 1 cent/kWh ops. Total 9.4 cents/kWh. Maybe you have different assumptions. The ThorCon costs similarly came to 2.6 cents/kWh. We say “under 3”.
2. We do have 2 heat exchangers plus steam generator; we can still load follow readily.
3. Graphite design limit for us is 4 years, due to size changes from neutron irradiation based on ORNL experimental data. Then we swap out and reuse or recycle.
4. SS316 is used in ThorCon except Alloy-N in 1-2 high-temp, low flux places. Cost estimates are based on no benefit from recycling.

Sean OM's picture
Sean OM on Jan 18, 2017 4:03 am GMT

Residential solar, even with a few hours of storage per the Kauai system, can dispace some fuel usage but not transmission needs, not even during all the peak load hours which continue past sundown.

The AES system they just added is actually their battery based peaker plant that they just added solar panels to.

Depending on where you locate the batteries, you may not need additional -line- capacity to meet peak demand. I mean that is kind of the point of peakers. You put them a lot closer to demand.

What you are trying to do is to get the demand down during the middle of the day during the peak hours. The new peak at the end of the day, typically isn’t as big as the mid-day peak you just replaced so you don’t need to add additional line capacity, which in some areas is extremely expensive. Thus it saves everyone the cost of the new distribution.

Even if you go the battery route to alleviate peak demand, you have significantly more options on -where- to place it so that it you don’t incur significant line capacity costs.

Darius Bentvels's picture
Darius Bentvels on Jan 18, 2017 6:24 am GMT

You are right.
Thank you for the answers.
Success!

Sean OM's picture
Sean OM on Jan 18, 2017 7:20 am GMT

He makes it look easy. 10GWh of batteries is 7% of the Gigafactory’s yearly production once it gets ramped up.
They still have 33 years to buy them.

I am also guessing a density improvement of 2x in about 5-8 years. So that doubles the capacity of the Gigafactory.
Well samsung has since announced basically a doubling of the density by 2021 for cars.

Darius Bentvels's picture
Darius Bentvels on Jan 18, 2017 8:21 am GMT

In Germany they have a battery investment subsidy of now 19% for households with solar (70% of households also install a lithium battery which allows for >2,000 cycles as the discharge depth is usually fairly small (the systems come with a solar battery management system).

The subsidy will be 13% in 2018 and become zero in 2020.
The Energiewende authorities expect that in 2020 >90% of all new small rooftop installations will get a battery*)

House owner earns the investment back via the difference of ~16cnt/KWh between the price they pay to the utility for consumed electricity and the feed-in tariffs (for small rooftop solar now ~12.5cnt/KWh).

The situation in USA is different. But considering:
– the widely expected continued price decrease of lithium batteries;
– the coming (or increasing) tariff differences between feed-in and consumed electricity;
I expect similar battery developments in USA with a delay of roughly a decade behind Germany.

Now only few buy a bigger battery and go off-grid. Yet.
The question is when that development will become mainstream as future battery management systems imply that no attention of the house-owner is needed and battery costs continue to decrease.
Some estimate that 30% will go off-grid…
Though little chance it will occur in areas at high latitude as those have little sun during a long winter.
________
*) The decrease of the subsidy is less than the battery price decrease, so the share of new solar installations that install batteries grows over the years. That allows time for the market to develop better products, improve supply chains, etc. The program started halfway 2013 with 30%.

Darius Bentvels's picture
Darius Bentvels on Jan 18, 2017 8:28 am GMT

Mark,
With the electricity prices they have at Hawaii, I’m amazed that so few users went off grid,
With the lower Germam solar and battery prices, everybody with rooftop space would go off grid as it’s clearly cheaper.

Willem Post's picture
Willem Post on Jan 18, 2017 1:47 pm GMT

Hi Bob,

I agree with your numbers, as they apply to New England.

A PV installer sat at my kitchen table and showed me his spreadsheet to convince me of the economics of PV. I was unconvinced.

So, I got my laptop and showed him my spreadsheet based on 25 years and various costs of money, with and without subsidies, etc.

He was quite impressed, agreed my spreadsheet was much more complete and the cost per kWh was more accurate.

It showed costs similar to yours.

BTW. You mis stated the REC price.

The market price of RECs in New England is about 2.5 cent / kWh. Prices were 5 cent but have decreased due to oversupply.

Robert Hargraves's picture
Robert Hargraves on Jan 18, 2017 2:11 pm GMT

My source on RECs is the auction market results, shown in the graphic. Here’s the link http://www.srectrade.com/srec_markets/massachusetts

Solar RECs trade at higher prices than wind RECs.

Meredith Angwin's picture
Meredith Angwin on Jan 18, 2017 4:43 pm GMT

At the most recent meeting of the Consumer Liaison Group of ISO-NE, James Bride gave a short talk, which included a list of the different types of RECs in New England states. Here’s a link.

https://www.iso-ne.com/static-assets/documents/2016/11/2016_12_01_clg_me...

Willem Post's picture
Willem Post on Jan 18, 2017 5:39 pm GMT

Bob,
Run your curser across your graph.
It shows values like 240 c/MWh

Sean OM's picture
Sean OM on Jan 18, 2017 6:15 pm GMT

Especially when they are still building plants, like Tesla in NY, and there are about 6 panel manufacturing facilities being built in India.

Mark Heslep's picture
Mark Heslep on Jan 18, 2017 6:58 pm GMT

1. I calculated AP1000 in George as $16 billion

Virgil 2 & 3 for same AP1000 design and power, $9.5B

Helmut Frik's picture
Helmut Frik on Jan 19, 2017 6:43 am GMT

What would be interesting is what makes rooftop slar in the US so etraordinary expensive compared to german psrices. Eve more red tape?
I do not have statistics of the last months, but typical prices which get a contraact of offers published on important sites show around 1200€/kWp rooftop solar (5kWp) above 10kWp this shrinks to around 1000€/kWp when you search for good offers a bit.

Helmut Frik's picture
Helmut Frik on Jan 19, 2017 6:49 am GMT

Well, that “analysis has notthatbig value, given that the authors a geologists by education and well known oil and nuclear lobbyists. There is no clear economical calculation in the texts, and I guess the people who offered the price in question there did calculate a bit deeper if they can offer it.
E.G it is unknown what kind of batery is used. If its LiFePO4 I get cycle numbers of >5000, some cite 20.000 Cycles in recent times. No scientific evidence, I am too lazy to seach for good references this morning, but clearly the question of cycle numbers and battery types changes the economy of the project a lot.

Robert Hargraves's picture
Robert Hargraves on Jan 19, 2017 7:59 pm GMT

Are we looking at the same graph? I put my cursor on the end of it and it says $265, per megwatt hour.

Darius Bentvels's picture
Darius Bentvels on Jan 20, 2017 8:48 am GMT

The huge rooftop solar price differences between Germany and USA generated a.o. a study by MIT. They concluded that especially the higher soft costs (inefficient process in USA) are a major factor.

From my memory (don’t have the study at hand):

– Often house owners need a license from local authorities which takes time, paper work and often money (considerations such as fire risks, etc);
Not here in NL.

– House owners need a detailed license (many pages) from the utility. In NL we fill out a short form at a WEB-site, no license procedure.

– When the installation is ready, the utility sends someone who inspects before it can be connected (in NL no utility does that).

When you don’t have one yet, the local grid operator will install a smart meter (in NL all houses will have a smart meter in 2020; many have already);

– Staff of installation companies, etc. consist of much more office workers, marketing people, etc. Here the share of people who do the job (handling the PV-panels and installing them) is much higher.
So in USA these companies need and take a much higher margin.

All those license & inspection costs are in my eyes superfluous,
No house owner / installer who installs solar panels, will create an installation which may generate a fire. People install according to the standards (in NL NEN1010), as otherwise the insurance may not compensate in case of fire.

It’s a matter of (not) trusting customers & citizens at utilities & local authorities. Also due to the often backwards rigid monopoly structures in USA which allows utilities to distrust their customers.
All these extra costs don’t bring something good, as e.g. shown with electricity’s reliability which is in NL and Germany 6 – 8 times better.

Nathaniel Pearre's picture
Nathaniel Pearre on Jan 20, 2017 3:27 pm GMT

I agree. 80% efficiency inverter is very low, and 15% capacity factor is very low too. I’m examining solar data in notoriously fogbound Halifax, Canada, and even there we’re seeing solar resources at 14%. According to NREL [http://www.nrel.gov/gis/images/map_pv_us_annual10km_dec2008.jpg] about a quarter of the US has a resource of about 22% or greater (SouthWest), and you have to really look hard (Pacific NW) to find 15%.
Solar is still expensive, so you have a valid point. Why not avoid silly criticism by using at least average numbers, rather than dramatically poor ones.

Jesper Antonsson's picture
Jesper Antonsson on Jan 20, 2017 4:00 pm GMT

For once, a pretty decent comment from you. Now apply this thinking to nuclear, multiplied by 100, and then you know why red tape and a lack of trust has nuclear semi-expensive in the west, while it was cheap historically and still is, in select countries. Also, this huge overhead drives reactor sizes upwards, which in turn makes projects more prone to uncertainties and increases cost of money.

But yeah, I forgot nuclear power is oh-so-dangerous and actually need agencies such as the NRC to slow everything down every step of the way and charge money for it. In fact, the lower radiation levels we have, the more harmful they seems to become. At least if one is to believe Busby, Scherb and the other authorities on low-level radiation that you like to quote.

douglas card's picture
douglas card on Jan 20, 2017 4:15 pm GMT

1. The $30 is completely meaningless and serves no purpose.
2. Which brand of Solar panel has lasted less than 25 years ON AVERAGE? The correct figure to use is probably 30 years, but certainly more than 25.
3.15 year loan at 5% is $7500 and about $6300 if you put down 20% or $3000
4.I’m not doing the rest of your job for you, but my guess is this is a little closer to $.20/kWh
5. In the Southwest its around $.15 /kWh and dropping fast, but since I only have to pay $.31 per kWh to S C Edison, the numbers just don’t work for me. (sarcasm)

douglas card's picture
douglas card on Jan 20, 2017 4:22 pm GMT

Considering the temperature of the last 3 years, these numbers are almost pointless, even if corrected, since this change is not an option and solar/wind WITH storage will be cheaper than any potential FF source in less than a decade.

Mark Heslep's picture
Mark Heslep on Jan 20, 2017 7:24 pm GMT

electricity’s reliability which is in NL and Germany 6 – 8 times better.

Those figures are all about the use of nearly universal underground power lines in NL and Germany behind the substation, having nothing to do with generation.

Underground transmission comes at a cost premium. An outage of once for a few hours every two years as opposed to once every twelve years may not be worth it. Indifference by residents and backup at some emergency facilities is a different way to go.

Mark Heslep's picture
Mark Heslep on Jan 20, 2017 7:42 pm GMT

If the argument is to be one of immediate climate imperatives, then the observation that France drove it’s fossile share of the grid to less than 10% in 14 years via nuclear means nuclear supercedes all alternatives, especially given US wind and solar remain 5% or so

Darius Bentvels's picture
Darius Bentvels on Jan 20, 2017 9:47 pm GMT

France realized its mistake and is now reducing nuclear share faster than Germany! They target <50% in 2025.

Robert Hargraves's picture
Robert Hargraves on Jan 22, 2017 12:30 pm GMT

Here’s real data from Hawaii, illustrating that the average capacity in this most southern state is under 20%. NREL may be optimistic.
https://s28.postimg.org/437xewv65/Untitled.png
from Energy Matters
http://euanmearns.com/can-hawaii-go-100-renewable/

Ivy Main's picture
Ivy Main on Jan 23, 2017 4:10 pm GMT

Saying utility solar is cheaper and therefore we shouldn’t have rooftop solar is like saying factory farming is cheaper and therefore we shouldn’t have home gardens. They are different, and both have advantages to society. Cheap isn’t everything.

Jesper Antonsson's picture
Jesper Antonsson on Jan 23, 2017 8:17 pm GMT

With the minor difference that France actually isn’t closing any nuclear, and president Hollandaise will be ousted this fall and his reduction to 50% in 2025 won’t happen. However Germany has shut half its nuclear already and will shut the last 14% until 2022.

Fact remains: France’s nuclear is a success story and achieved decarbonization at low cost three decades ago. Germany’s energiewende is a major disaster and achieves nothing but very high costs.

Jesper Antonsson's picture
Jesper Antonsson on Jan 23, 2017 8:22 pm GMT

No, rooftop doesn’t have advantages. It stands in the way of rational tracking solar. We have this huge task of decarbonization ahead of us and this isn’t a time to indulge greens and progressives that want to get higher status by spending other peoples money on their roofs.

Jesper Antonsson's picture
Jesper Antonsson on Jan 23, 2017 8:26 pm GMT

Can you point to real research into solar panels longevity? Of course, survivorship bias means current old solar installations are old, but that doesn’t say anything. Furthermore, we’re now buying very cheap Chinese solar panels. Every corner that can be cut has been cut. How long they’ll last is anyones guess, but we can be pretty confident few current players will be around to honor guarantees in 15 years from now, even.

Mark Heslep's picture
Mark Heslep on Jan 24, 2017 4:13 am GMT

NREL 2012: “Photovoltaic Degradation Rates — An Analytical Review”

Mean 0.8%/yr, median 0.5%. If still accurate, this means that, for instance, Germany’s solar fleet decays at 320 MW/yr.

http://www.nrel.gov/docs/fy12osti/51664.pdf

Mark Heslep's picture
Mark Heslep on Jan 25, 2017 2:20 am GMT

As a completely self financed hobby for somebody that for some reason desires to go off grid with an expensive solar and a generator behind the curtain solution, have fun.

I have a vegetable garden. But even the home vegetable garden would be a disaster in some misguided scale-up attempt to supply a significant fraction of the food demand. The use of land, chemicals, water, and man-hours is vastly less efficent relative to the professional farm.

There are other garden-rooftop solar parallels. The garden sometimes fails completely via weather, insects, deer, or general amateur incompetence, and, like solar users on the grid, off goes the garden owner to the grocery. Now, multiply gardens a million fold. Perhaps use a net-food-metering program where grocers are required to buy excess from the garden. Scale up occurs mainly via the well-off with a spare half acre of land in suitable climates and time to manage it. The cost to the grocer per unit sale escalates, borne instead by the not well-off in apartments with no estate in the country.

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