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Inflation-adjusted residential costs according to nrel.gov are shown in the chart on page vi of https://www.nrel.gov/docs/fy17osti/68925.pdf

The raw costs, not adjusted for inflation:

Q1 2014: $4.52/W total for $1.03/W modules [0]

Q1 2015: $3.09/Wdc total for $0.70/Wdc modules [1]

Q1 2016: $2.93/Wdc total for $0.63/Wdc modules [2]

Q1 2017: $2.80/Wdc total for $0.35/Wdc modules [3]

Conclusion: Even if the modules cost $0.0000001, the total price could not fall much more unless the rest of the business model gets updated. Probably some solar installer companies will drop out of the market, and the survivors will adapt to lower profits.

[0] Page 12, https://www.nrel.gov/docs/fy14osti/60401.pdf

[1] 5.2kW system. See page 7, https://www.nrel.gov/docs/fy15osti/64746.pdf

[2] 5.6kW system. See page 16, https://www.nrel.gov/docs/fy16osti/66532.pdf

[3] 5.7kW system. See page 21, https://www.nrel.gov/docs/fy17osti/68925.pdf

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Based on the Australian experience, the next wave of price declines for residential solar will indeed come from balance-of-system cost declines, increased installation efficiency and lower profits.

Current costs in Australia are about A$ 1.70 /pk-W (~US$1.35), pre-subsidies, split roughly into 35% modules, 10% inverter, 10% mounting system, 10% other hardware (cabling, switchboard etc), 10% installation and 25% "vendor's margin", including marketing, sales and profits.

The household has also to pay for a bi-directional meter to allow for energy sales. IIRC that was around A$350.

It's a mystery why the US costs are so high - maybe not enough competition?

Probably not enough interest.

It'd be interesting to see the costs split out based on available sun. I would guess they are lower in Phoenix than in Connecticut.

Energy costs are significantly lower in the US.

Most of the northern states don't have much sunlight and have cheap enough power to make it not worth it.

A common misconception. Even in northern Sweden, which is above the arctic circle, you can still generate ~80% of the energy that Southern Europe generates.

This is fascinating if true. Do you gave any sources, I'd be really interested in reading more on the matter.

This gives a good overview. What people miss is that during the summer the sun is up all the time. (In the winter, not so much.) And average cloud cover is also accounted for.

http://re.jrc.ec.europa.eu/pvgis/countries/europe/EU-Glob_op...

PVGIS is an excellent tool and I have been using it for years!

Thanks! That is quite surprising, and very encouraging.

It seems that solar is a very good overall fit for even most of the world, and once the tech is good enough to be used in huge numbers the differences can probably be compensated with other, local power sources (like hydro in Scandinavia, which is huge there).

Do I understand correctly that the wishful thinking value of 75% photovoltaic conversion efficiency is plotted in the diagram?

It means the conversion factor of yearly yield in kWh to installed PV in kWp. "Yearly sum of solar electricity generated by 1 kWp system". It's not about the physical PV efficiency.

The 75% performance ratio represents system losses not module efficiency. So a system rated at 1kW(peak) which may be 5-6 square meters in size, and which is exposed to annual sunlight of 1200 kWh/m2 might only produce 900 kWh of usable power.

So efficiency has to do with the rated power per surface area and the performance ratio reflects all the system electrical and environmental factors that reduce the amount of usable power below what would be expected based upon module ratings and annual sunlight exposure.

That diagram suggests Northern Sweden to Southern Europe is 50%, not 80%, which sounds more plausible.

> What people miss is that during the summer the sun is up all the time. (In the winter, not so much.)

It sounds like these two effects should cancel each other out. Are you saying that people take winter into account but not summer?

Depends on what you're using it for. A common use-case is cottages that run off the grid, which are only used in the summer half of the year anyway.

But cold panels produce more power.

See the comment from bjelkeman! I don't have any "hard" sources but reserarching solar panels for myself by hanging around Swedish solar forums and noticed people way up north still get a good yield from their panels.

Most of the energy comes from ambient light, direct light is best of course but not strictly needed

Nitpick: Only the northern tip of Sweden is north of the polar circle. But yeah, Sweden is pretty dark anyway.

One factor that helps is that solar cells become less efficient if temperature goes up (https://www.thegreenage.co.uk/article/the-impact-of-temperat...)

This is a good introduction & has excellent maps. http://solarinsolation.org/tag/map/page/2/

It's a combination of the 80% output and the cheap local hydro power which makes it not attractive.

It's true that power here is cheap (~0.1€ per kWh). However, since most electric companies buy back what you overproduce you can get an installation that covers your whole years supply and have it paid of in 7-10 years.

Here in Maine your solar panels are going to be covered with snow 5 months of the year, so the power production in the winter can't be very significant.. It's one thing to store energy between night and day and it's another thing to store energy between summer and winter. Don't get me wrong, I think solar is the future, but not sure how to make it work up north.

In curious about this, does it snow so heavily for 5 months there would be no way to clear the panels?

I mean they're installed at an angle to start with so how does the snow build up? Could panels not be designed with inbuilt defrosters?

The snow could be cleared off with a shovel, but then you have to either pay someone to do it in the case of industrial solar, or in the case of home solar, go up on your roof when it's covered with ice and snow, not the safest maneuver. Defrosters might be possible but that might use more power than the panels generate. You'd have to raise the temperature of the panels to above the freezing point of water, which might be a change of 20 or 30 degrees F on really cold days. Some years are worse than others- 2014 was really bad, I didn't see bare ground until late April.

I live in Massachusetts, and have 37 250 watt panels. Snow isn't an issue. The panels generate a little bit of resistive heat, which means snow typically doesn't stick. If it's snowing so heavy, and is so cold that the panels do get covered with snow, the snow melts and slides off within an hour or so.

In July my panels make 1300 kwh and in December and January they make 300 kwh, mostly because of the angle of the sun and the length of the time above the horizon. I also have significant southern tree cover, so my production is not optimal for my area.

What about some place like California?

It has sunlight almost all year round, it has a pretty progressive government, and a leading tech sector. With house prices being so high, so the cost of solar panels would be relatively lower too.

They also have a crazy amount of NIMBYs. Though they might not have figured out how to object to solar panels, yet?

in Los Angeles, solar panels are becoming increasingly common on single family dwellings.

as more and more existing trees die off because of higher water costs and a general theme of reduced water usage, there's a little bit less shade, too.

It's worth noting that in Queensland, we saw a big decline in cost after the feed-in tariff was dropped substantially in 2012, reducing demand. I paid AU$8500 for a 3kW system when I could lock in a 44c feed-in tariff, but everyone knew there was a deadline looming that wasn't changing. Once that deadline hit and it dropped to 6c, demand for installs dropped and the subsequent price dropped towards where we are now. Essnetially, panel and other equipment supply (as well as labour supply) overcame demand and the price fell as a result.

We also had the renewable energy credits scheme which made the price float about a bit since they were a traded commodity and the installer would take them off you for a price reduction proportional to their market value (if you elected to not instead keep them for yourself and pay 'full' price, but then have to sell them yourself too).

Basically what I'm saying is that there were multiple levers causing the price to float around a lot over the last 5-8 years and it's not strictly just because gradually supply/competition grew.

Based on that, shouldn't it be possible to get close to a 35% price decline, as long as the government allows you to buy wholesale and self install?

It would be great to see a DIY community around this, making widespread adoption even cheaper.

You can definitely get a monetary price decline from DIY. But most people's time has value, too.

Not sure what your lifestyle is like, but I think you would be surprised by how many people are willing to do weekend DIY projects on their homes, especially if they will save them money.

A properly done and code-compliant residential rooftop solar install is non-trivial for many DIYers. I do lots of things around my house but a rooftop solar install is something I'd definitely hire an experienced and insured contractor for.

Your typical DIYer is unable to penetrate an asphalt shingle or metal roof and properly waterproof those penetrations for the panel frame supports, voiding your roof warranty and possibly negating any ability to make a claim for water damage from your homeowner's insurance.

Also, any electrical work in most sane jurisdictions is going to require signoff from both the local code department and the utility (if grid tie).

The labor of a professional is cheaper than possible poor outcomes.

Ok, I can appreciate those concerns, but if someone wants to do this, I think that's their right. What if they have a cabin that they want to wire with solar? What if they just want to setup some panels on top of an awning, or in their backyard, and hook them up to a beer cooler?

To be fair I installed a solar+2nd battery+inverter that can also charge or be charged from the primary battery in an RV. I waterproof'd the roof, did the wiring, there's lots of guides on how to do it and it is not rocket science. Should you or my local gov have stopped me from this?

> Should you or my local gov have stopped me from this?

The government isn't stopping you from putting solar panels on the top of your RV, and it's regulation of structures through building codes is usually reasonable.

You might be interested in reading about the Tiny House movement. I think you would be surprised by how many people Rdisagree with you, and are upset with draconian housing laws and building codes.

Again, I don't see an enormous difference b/w putting solar panels on an RV, and a backyard, shed, cabin or house, particularly for off-grid power.

You are absolutely entitled to state your opinion though. I just think if other people want to do something that doesn't bother you in any way, it can be nice to warn of the risks, but why tell them they are wrong?

> I just think if other people want to do something that doesn't bother you in any way, it can be nice to warn of the risks, but why tell them they are wrong?

Because if you're breaking building code, you're breaking the law. That's the entire reason the Tiny Home movement has to build their structures on RV trailers; to be compliant with building code (which doesn't apply to RV trailers).

Ok no one is saying you should break the law, and that also wasn't even your concern in the previous comment, either, which was about the reasonableness of building code. Before that you were primarily concerned about time and risk of cost.

Bringing the goal posts back to the original aim of my comment: that a DIY community would simply increase adoption, let's look at the Tiny House movement. It grew as a DIY community. People sharing info on all parts of the process, incl. building code, helps many people who would have been told by someone that it can't be done, just as you are doing now, to build their own house. And we are talking about building an entire house, not a minor solar panel install.

As that community grows, you have more people that are able to even shape laws for the better, which is what that community is doing.

And you are incorrect about there being no laws governing auto work and customization.

No one is saying you should do this. To be frank, the "hire a qualified contractor" advice is pervasive at HN, but it's also this groupthink attitude of negativity that can grow around a subject that I don't think is necessary, or helpful.

Yes. Though of course, solar panel installation still has opportunity costs.

Eg even if you don't want to get a second job, you could still be lazing about, spend time with family, do another DIY project, or even commute to a job in that time.

(Commuting decisions usually can't be changed in the short term, but in the long term it's up for grabs just as anything else as people contemplate moving or changing jobs.)

Yes, it does. But outside regular work hours, it's hard to get a meaningful return on those hours - something as costly, yet relatively easy (if laborious & monotonous) as installing solar panels/shingles, makes for an attractive DIY.

> But outside regular work hours, it's hard to get a meaningful return on those hours - [...]

I mostly agree. Of the top of my head, installing solar panels mostly competes with leisure and other DIY projects.

Perhaps also with commuting, but for most people the decision on how long to commute can't be altered in the short term.

Maybe... but in Australia, the system must, by law, be installed by an accredited installer to be eligible for the "small scale technology certificates", a form of subsidy. This is currently worth about 45% of the pre-incentive cost. The accreditation itself is fairly straightforward, but costly.

> The accreditation itself is fairly straightforward, but costly.

As is typical in Australia, to do almost any job you need to purchase that right. Even construction labourers (guys carrying out the bins and sweeping floors) and waitresses who serve alcohol, need an accredidation.

> Conclusion: Even if the modules cost $0.0000001, the total price could not fall much more unless the rest of the business model gets updated.

Which is where solar roofing comes in, taking up the cost of installation almost completely and dropping price almost to grid scale. Of course, the only solar roofing available forces you to get it installed by their technicians, but hey. Baby steps.

The discussion in your first link is interesting. Smaller installers can end up having lower costs because they spend less on customer acquisition. They pay somewhat higher prices for material, but plummeting panel costs and not holding panels in inventory have worked out well for them.

This sounds like inverse economies of scale. Interesting.

Thanks to your comment I looked this up. There is actually a term for this. https://en.wikipedia.org/wiki/Diseconomies_of_scale

Tesla's approach of taking the solar installation and "baking it into" changing the roof is very interesting in this regard, long-term. A labor-intensive job is done in parallel with another labor-intensive job, with a good amount of overlap.

>>Conclusion: Even if the modules cost $0.0000001, the total price could not fall much more unless the rest of the business model gets updated.

Sure, when building the roof, it is installed as a solar one, saves on roofing materials and installation, since you only pay for solar and for solar installers. Granted not 100% substitution since not all the roof can be covered but a nice chunk.

Or make the panels more DIY...a few cases of beer, a few friends and be done. (plug it in after 24 hour, to make sure that the beer is gone from system)

not to dispute the concept of an easy solar install, in theory, but i note add that, in Los Angeles at least, it's hard to imagine a quick, low-cost, DIY solution.

to the LA Department of Water and Power, home solar is basically competition. and the DWP is an important cash cow for city workers and the city budget. they will find ways to add customer fees and reduce the customer's energy bill savings. (e.g. limiting the amount of electricity a home is allowed to feed back into the grid.)

the agency and the city simply need that cash.

So from 16 to 17, the total cost aside from modules went up?

I haven't collected the hard numbers for what is presented on page vi of https://www.nrel.gov/docs/fy17osti/68925.pdf, but soft costs appear to have swollen to take up most of the cost savings from reduced module prices.

In other words, yep.

Here are the exact numbers that went into the figure you reference, the key costs findings by category for 2010-2017: https://catalog.data.gov/dataset/nrel-u-s-solar-photovoltaic...

Soft costs decreased appreciably from 2016-2017 in both "utility-scale" categories (Fixed-Tilt, and One-Axis Tracker), and have increased slightly at the smaller "commercial" and "residential" scales. Across all scales, soft costs claim a larger portion because other costs are falling more quickly.

Only at residential scale has soft cost growth consumed much of the savings in other costs: $-0.18/(watt installed) total cost, $+0.16/(watt installed) soft costs.

At commercial scale: $-0.32/(watt installed) total cost, $+0.05/(watt installed) soft costs.

While this direction of change is certainly suboptimal, I don't think the magnitude is worrisome yet.

EDIT: paragraph/line breaks for clarity of presentation.

Which from an outsider perspective could have been companies recouping on bets made (discounts offered) in 2016 to grow their brand recognition, etc. It's hard to draw too strong a conclusion from data for for so few years, where costs change so much, and the outlier is the most recent year (which is also incomplete). It's also possible that the actual business costs from year-over-year operation are finally becoming well known, and the installation costs are finally reflecting items that weren't correctly priced in earlier (botched installation fixed, warranty repairs, etc).

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