File talk:1975 – Price of solar panels as a function of cumulative installed capacity.svg

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Comparison to earlier version[edit]

Solar-pv-prices-vs-cumulative-capacity
This graphic: more readable, less text —RCraig09

I prefer the older version of this diagram, because it includes more information:

  • data points had years (maybe every 5 years a timestamp is enough) and this allowed to make a connection between cumulative installed power and the development in time.
  • learning rate was given as a very relevant parameter.

--Gunnar (talk) 14:53, 3 October 2023 (UTC)[reply]

@Gunnar.Kaestle: Thanks for your comments.
— I plan to add labels for each five or ten years. I will upload a Version 3.
— I think it's important to update the charts with more recent data.
— There have been long discussions, especially related to climate change, about the size of fonts in images. The fonts should be about as large as the text in the articles, and text should generally be minimized in graphics. Most people read Wikipedia on portable devices, which have small screens, so we editors try to follow this guideline. The text in File:Solar-pv-prices-vs-cumulative-capacity.png is tiny.
— I have explained the "learning curve" in the text captions, in the Wikipedia articles. Explanations of the "learning curve" require too much text to include inside the graphic itself. File:Solar-pv-prices-vs-cumulative-capacity.png contains too much text, including unnecessary sourcing and other explanations. The explanations can be in captions, or in these Wikimedia file description pages.
I hope you understand my approach. RCraig09 (talk) 16:05, 3 October 2023 (UTC)[reply]
I have uploaded Version 3. It labels years, 1980, 1990..., and includes the legend "► "Learning curve" ►". RCraig09 (talk) 16:57, 3 October 2023 (UTC)[reply]
I agree that the font in diagrams should be as large as possible to support a better legibility. The term "learning rate" is already defined, so there is no need to explain what learning rate means, see en:experience curve effects: 1 minus the progress ratio is the learning ratio, and this number defines the mathematical expression which is depicted in the log-log-diagram. "Learing rate = X %" is the technical term which gives some defined information. The term "learning rate" is easier understood (higher learning is better than low learning rates) than the progress ratio.
A straight line in log-log-display is equal to X % learning rate; it depicts the unbroken trend in cost reduction, and this is the quintessence of Swanson's law. The original curve had this dotted line and said it's equal to a learning rate of 20,2 %. If you update the diagram with a 3nd edition, please cover this information on the learning rate parameter as well as this is more crucial than knowing what happened in the last 2 additional years. --Gunnar (talk) 17:09, 3 October 2023 (UTC)[reply]
Thanks. If you still want feedback:
* change the title to "specific costs of solar modules", as the costs per unit of power is shown.
* the Y axis should not be labelled in "costs per module" but "price per Watt". We do not know what the production costs are, but the market price is assessed. We do not know how large a module is, usually the price is given per kW or Watt as in this case.
* The cross picture arrow is too dominant. Use a thinner one or make it green (not black) and do not talk about learning curve but say learning rate = XX,X %. --Gunnar (talk) 17:19, 3 October 2023 (UTC)[reply]
@RCraig09, one additional point: Please look into your original data and look what kind of dollars have been counted. Usually for long lasting price series, there is an inflation adjustment and the base year is given. This reference should be mentioned in the X axis label: e.g. price per Watt in USD2021. --Gunnar (talk) 17:27, 3 October 2023 (UTC)[reply]
@Gunnar.Kaestle:
1. The source explains "Data is expressed in constant 2021 US$ per Watt." (even though their axis label said "Solar PV module cost"!). I plan label the axis "Cost per watt", and put "Constant 2021 US$" in the lower left, in small print (less distracting).
2. I plan to make the arrow label say "Learning rate=20.2%".
3. I now prefer the title "Cost of solar power" because the vertical axis is dollars per watt.
4. I'm not sure what you mean by "cross picture arrow"—the diagonal arrow, or the horizontal arrow? I'm thinking of making both thinner.
RCraig09 (talk) 20:52, 3 October 2023 (UTC)[reply]
1. The whole graph depicts the "specific price of solar modules", the inflation adjusted US$2021 is part of the legend for the Y-axis because the dollars are part of the units which are counted (dollars per Watt).
2. Are the 20,2 % the same learning rate from the previous graph, or is this a value which has been calculated from the 1975-2021 data?
3. "costs of solar power" is wrong, because that are the levelized costs of electricity in ct/kWh, which also includes the [1] insulation at the site of the PV installation: costs of solar power depend of the solar yield, not only what the specific price is for the PV modules (and other equipment such as inverters, cabeling, mounting, etc.).
4. Yes, make both arrows thinner. I meant the diagonal one - maybe this one does not need to cover the full diagonal length, but only should indicate the direction that with higher cumulative production, the price goes down. --Gunnar (talk) 21:12, 3 October 2023 (UTC)[reply]
I went ahead and uploaded Version 4, because the vertical axis label in Version 3 was wrong. I hope you agree with Version 4. I'm open to more suggested changes. Thanks for your explanations. RCraig09 (talk) 21:05, 3 October 2023 (UTC)[reply]
As I wrote above, the title "Costs of solar power" is simply wrong, as one would expect the levelized costs of electricity in USD per MWh or similar. What is seen on this graph are the specific prices for PV modules only, excluding other equipment you need for a working PV system and excluding the amount of sun shining where the PV installation is commissioned.
There is a fine difference between (production) costs, (market) prices and (consumer) utility. What is seen here is a market survey on a specific market segment - I do not expect that you can buy for 300 USD/kW the panels for a small residential type of PV system, but that's rather the specific wholesale price.
"In the expression of a quantity value, there is always a space between the numerical value and the unit symbol." (Rule from science and technology: 9.4 Values, intervals and tolerances [2]) Write "100 $" instead of "$100".
As the script is very tiny that says the scales are logarithmic and as it is obvious that they are logarithmic, just remove this note. Also the same tiny script is used for the reference year for inflation adjustment. It is better to specify it just in the legend: Specific costs in US$2021 per watt, then you don't need to repeat the unit behind each value on the logscale. --Gunnar (talk) 21:43, 3 October 2023 (UTC)[reply]
I'm not understanding all your explanations, so I'm not sure how to make specific changes. Please be explicit and specific in exactly how you think the chart should be changed, especially re the axis label, and the chart title. Thanks. RCraig09 (talk) 21:58, 3 October 2023 (UTC)[reply]
Version 5 is uploaded. (I forgot to change "Cost" to "Price" in Version 4, sorry.) I simplified the title to "Solar power" to avoid problems. The other issues are formal and less important: I followed the source re US$ and kept that text small to avoid distracting clutter. RCraig09 (talk) 04:05, 4 October 2023 (UTC)[reply]
  1. "Solar power" for the title is not correct. "power" means electricity in general, and there are two ways to convert the primary energy from the sun into electricity which are a) photovoltaic systems and b) solar thermal power plants. In this diagram, the specific price for PV modules are shown, nothing else. Not the costs of the full PV system including the inverter, the cabling, mounting, labour costs for installation etc., only the price of the PV modules. Say: "Development of specific prices for PV modules" as the title. It is longer that solar power, but you should label the diagram in such a way, that it is clear on first sight what it shows and to avoid that the reader must guess.
  2. In giving a quantity, the proper scientifically correct way is - as I gave you the example from ISO/IEC - "number + space + unit". You wrote in the y-axis "$100", "$10", "$1" which may be ok for a grocery store, but to avoid misunderstandings in the scientific literature there a clear rules how to express quantities and units, eg. the mass is 10 kg, or the consumed electricity is 523 MWh, or an USB port uses a nominal voltage of 5 V. Therefore you should say "100 $" and so on. Or even better and to avoid to repeat all the dollar signs, just say the the legend "Specific price of PV modules in US$/W" mentioning both what is shown (price of PV module) and the unit (in US$/W). If you don't want to integrate the base year 2021 but prefer to add this as a footnote in tiny script in the left bottom corner, that's acceptable but contradicts your motivation to get rid of illegible tiny script. --Gunnar (talk) 06:37, 4 October 2023 (UTC)[reply]

— Your suggestions, "Development of specific prices for PV modules" and "Specific price of PV modules in US$/W", use the English word specific in a very unusual way. It's not clear how specific prices are different from prices. Separately, "Development of" is apparent from the horizontal axis.
— Our audience is the general public, and many will not know what "PV" stands for. Beneath "Solar power", I plan to add "from solar panels"
— Again, our audience is the general public (laymen), not scientists. Sources for both charts use "$100", which laymen directly understand. Adding "$__" does not add separate words, and avoids distracting clutter.
— The details of inflation adjustment are not important to what the chart communicates. That's why I favor small font sizes (like the source) rather than large-font distractions. RCraig09 (talk) 15:05, 4 October 2023 (UTC)[reply]

  1. The specific weight is the weight per unit volume of a material. The specific heat capacity is the heat capacity of a substance sample divided by the mass of the sample. How do you call the price per watt if not specific price? An apple may cost 50 cent (= price of that apple). If this apple weights 200 g the specific price is 2.50 USD/kg; if it weights 333 g, then the specific price is 1.50 USD/kg. Therefore it is important to talk about the specific price. The unit for the specific price for a generator is USD/W. Usually, you use both in the legend: you name first what it is and then you give the unit: "Specific price in USD per watt".
  2. The audience is clever enough to know what PV stands for, especially if you look where this diagram is used: Renewable energy, Solar cell, Solar panel, Grid parity, Growth of photovoltaics, Swanson's law. This is an encyclopedia, so please be precise.
  3. Why do you think anybody could misunderstood "100 $"? And why do you think this rule has been invented to write "quantity - space - unit". Such as in: my car weights 2 tons - and not my car weights tons 2.
  4. The current diagram gives have of the units in the legend (per watt) and half of the units in the grid (100 $). If you put it together it is either all units next to the quantity "100 $/W" or more professionally, you have the units in the legend and only the numbers attached to the diagram's grid.
  5. If the chart is used as a data reference, it is important to give the base year. The only weakness which I pointed out is that you contradict your own arguments saying that you dislike small fonts. So, never mind.
  6. "Solar power from solar panel" could be anything, including the electric sunshine yield. What is shown in the diagram? Cost_of_solar_panels_as_a_function_of_cumulative_installed_capacity says the filename, which has been corrected. The diagram depicts how the specific prices for PV modules decline as a function of cumulative capacity, specific to the installed power. I like "module" more than "panel", because photovoltaics is a modular technology, but PV panel is a nice alliteration. --Gunnar (talk) 18:35, 4 October 2023 (UTC)[reply]
  1. The term "specific price" is not used in the references—or anywhere else I could find. Laymen will not understand your reasoning at all. "Specific" is a perplexing complication, especially for laymen.
  2. The audience (of laymen) should not have to be "clever" and look outside the chart for what "PV" means. I can add the full word photovoltaic in the title if you want.
  3. I didn't think anyone would "misunderstand" "100 $/W". Laymen simply don't use it. Our audience is a lay audience.
  4. Almost every chart I've seen—including both references here—use "$100". It is what our (lay) audience directly understands.
  5. Like both references, I have used small fonts from the first version. I do not dislike small fonts: they are less distracting for background information.
  6. I don't know what you mean by the file name "has been corrected". In view of paragraphs 1-5, is "Solar photovoltaic power" an acceptable title? If you want a subtitle, referring to modules, please be specific in your suggestion. Long explanations aren't necessary. Please provide an explicit quote.
— RCraig09 (talk)
  1. How do you call the price per unit if not specific price? The purpose is to differentiate between the price for single items (which may have different sizes like in the apple example) and the specific price (per kilogramm of precious metal, per meter of rope, per cubic meter of gas, etc.).
  2. Photovoltaic is fine you prefer this. Say: "xxx prices for photovoltaic modules" and use for xxx the answer you give for question 1, as we are not talking about the price of a dedicated PV module, which may have a peak power 300 W, 350 W, 400 W etc.
  3. I don't think anyone would misunderstand "100 $/W" either. So let's use professional style in graph design, which you would also use in scientific papers: quantity - space - unit. If you are not using this method, it says nothing about your audience, it simply says that you as a creator are a layman which is unwilling to apply the rules of properly handling quantities and units.
  4. Directing your arguments on the expected layman audience makes no sense, because you say indirectly: laymen make mistakes, they expect mistakes, so let's give the mistakes. The specific price per power is given in $/W and not in $. This is a question of correct and wrong.
  5. I agree that small fonts are not very well legible, and should be avoided if possible. It is ok to keep the fineprint, if that's preferred by you.
  6. The file name says "costs of solar panels" - I am happy that you did understood that there is a difference between costs and price and we are talking about an overview on (wholesale) prices in this diagram and not about (production) costs. "Solar photovoltaic power" is pleonastic, as photovoltaic is the conversion of solar energy into electricity: any kind of PV is automatic connected to solar. What is shown in this diagram is a curve of prices for PV panels (not for PV inverters) - this is fundamental and has to be part of the diagram's title: "xxx prices for photovoltaic panels" ("modules" is also ok with the modular PV technology). xxx means the synonym for (size) specific, which you use. --Gunnar (talk) 16:34, 6 October 2023 (UTC)[reply]
??? Bottomline: I'm asking for your preferred title for the entire diagram—without explanation. RCraig09 (talk) 16:44, 6 October 2023 (UTC)[reply]
xxx prices for photovoltaic panels --Gunnar (talk) 18:51, 6 October 2023 (UTC)[reply]
Re: Version 6:
— Probably, the closest "xxx" word is "unit", similar to the common term, unit price. "Unit" = "1". However, if we were to say "Unit prices for photovoltaic panels", it would imply the prices are $ per panel (wrong), not $ per watt (correct). This is why I have added a completely different title description, "Declining prices...". (Its meaning is not related to "unit".)
— Separately, it is important for the layman to see the word solar in the title, so I have added "(solar)" in parentheses to contextualize the technical term, photovoltaic.
— Our main goal is to communicate to laymen, not only accurately but in a way that's easy for laymen to understand without puzzlement or research. Other issues from our preceding paragraphs are formal, so I have not made additional changes other than to add small subtext under "Learning rate...".
Thanks for your time. RCraig09 (talk) 20:45, 6 October 2023 (UTC)[reply]
Even laymen are able to read Wikipedia articles, such as en:photovoltaics. Writing "photovoltaic (solar) panels" is not only pleonastic, meaning you can cut off some letters from this title without loosing information, but it may also irritate laymen because the might get confused between solar panels that produce electricity and solar panels which produce heat. "photovoltaic panel" is perfectly fine, shorter and more precise. --Gunnar (talk) 14:36, 7 October 2023 (UTC)[reply]
We simply disagree on whether laymen should have to go to another article, in order to understand a word in a graphic; I think they should not be forced to visit another article because most will not visit another article. As I see it, the only reason to include "photovoltaic" at all, is to distinguish from concentrating solar, etc. The chart distinguishes from thermal collectors by including both "photovoltaic" (technical word) and "solar" (layman's word). RCraig09 (talk) 16:10, 7 October 2023 (UTC)[reply]
Your "layman" argument is wrong if you want to prevent the use of precise terminology, it is ok in the depth of details (see introduction for each Wikipedia article compared with later paragraphs). Solar energy can be harvested in 3 different ways:
  1. photovoltaics to produce electricity,
  2. solar thermal collectors to produce low temperature heat,
  3. concentrated solar power to produce high temperature heat which is converted via a thermal power plant into electricity.
By not using the correct term "PV panel" but adding some solar to the mix, you increase the risk that a layman will misunderstood option #1 as #2 or #3. "photovoltaic panel" is biunique, but solar is not. You don't help laymen by not using precise terms, as they need more know-how to choose correctly the subcategory of the umbrella term "solar". Photos comes from Greek 'light' as in photon, photography, photosynthesis, etc. so please trust that people will understand this term or know where to dig deeper - they have already done this when using a wikicommons figure. By the way, several million people have a PV system on their roof - thus it is quite common. But still some people mix up panels which produce solar heat and solar electricity, as both technologies are widespread. --Gunnar (talk) 21:54, 8 October 2023 (UTC)[reply]
I understand the difference among #1, #2, #3. Placing "(solar)" in parentheses ensures people will associate photovoltaic panels with what they commonly understand: the commonly-used term "solar panel" gets 56.1 million Google hits, but the technical term "photovoltaic panel" gets only 1.56 million hits—a 35.9/1 ratio. Placing "photovoltaic" without parentheses ensures people will understand "photovoltaic panel" is the technically proper term. They will not confuse #1 with #2/#3—especially since few layman know about "thermal collector" (<1 million hits) or concentrat{ed/ing} solar (~3 million hits, total) to begin with. Many lay readers would have no clue what photovoltaic means, or ponder the word root photo to deduce it has to do with light. RCraig09 (talk) 22:39, 8 October 2023 (UTC)[reply]
I think you don't realize that the vast majority of readers don't possess your level of knowledge. WP:ONEDOWN is somewhat relevant here. RCraig09 (talk) 22:45, 8 October 2023 (UTC)[reply]
I've just uploaded Version 8 with the title, "Declining prices for photovoltaic panels for solar energy"—longer, but explanatory. I hope this change solves any issues. RCraig09 (talk) 00:36, 9 October 2023 (UTC)[reply]
You make it worse than improving it. "declining prices for photovoltaic panels" is perfectly fine. The last line may - again - giving a laymen a wrong idea what is happening. These panels are for producing electricity, there are using solar energy. But how a PV panel works should be not part of a diagram's title, that's part of the photovoltaics article. WP:ONEDOWN is on articles, not on diagram titles. I really don't understand why you cannot accept simple advice from somebody who gives one justification after another. Two lines. Please, that is enough and perfectly describing the content. "photovoltaic" can be found by anyone who has found Wikipedia and knows how to use the search function. --Gunnar (talk) 20:04, 9 October 2023 (UTC)[reply]
  1. I have read your advice many times. I simply disagree, at least in part because this is a layman's encyclopedia and not a doctoral thesis.
  2. Illustrations are part of articles, so that WP:ONEDOWN applies.
  3. For reasons given on 8 October, the previous title and the Version 8 title are not misleading: "photovoltaic" distinguishes over thermal panels and solar concentrating (with which laymen are probably not familiar in the first place!). The words, "for solar power", contextualize in layman's terms the technical term (photovoltaic).
  4. We simply disagree as to whether the layman—who probably does not have any idea what photo or "photovoltaic" mean—should be expected to search for the meaning of a word in a title. Illustrations should illustrate, not perplex. RCraig09 (talk) 21:29, 9 October 2023 (UTC)[reply]
  5. Compare Google searches for "solar panel" versus "photovoltaic" — a ~15/1 ratio, with "solar panel" searches growing and "photovoltaic" declining. https://trends.google.com/trends/explore?date=all&geo=US&q=photovoltaic,solar%20panel&hl=en —RCraig09 (talk) 20:34, 10 October 2023 (UTC)[reply]
  6. Interestingly, Britannica approaches the subject in this way: "Solar panel / Also known as: PV panel, photovoltaic panel" — naming the article with laymen in mind. RCraig09 (talk) 05:34, 12 October 2023 (UTC)[reply]
    It is not a question of onedown, it is just an issue of unprecise language. Please give a proof that laymen are not able to identify the meaning of photovoltaics. Solar is an umbrella term which does not specify the subject correctly, similar to "hat" and "Fedora". Interestingly, the Britannica article forgets to mention that panels which collect solar energy in the form of heat are not PV panels. For the real layman, this is crucial information. Besides you forget to answer the weakness that the wording "panel for X" usually means that X is produced - in this case it is electricity. --Gunnar (talk) 17:57, 14 October 2023 (UTC)[reply]
  1. The Google search results, and Google Trends for search terms, (both presented above) prove that "photovoltaic" is not sought after or commonly used by ordinary people. I do not have to "give a proof that laymen are not able to identify the meaning of photovoltaics", because the issue is whether they should have to work (go to another article) to find out the meaning of a term in the title of a graphic! The current title explains, not perplexes.
  2. The term, "Panel for X" does not state or imply that the panel produces X. The clear meaning of the title is that the panel receives solar energy. You can purposely misinterpret the phrase, but the meaning is clear to ordinary people. RCraig09 (talk) 22:32, 14 October 2023 (UTC)[reply]
Update: Version 9 recites "(convert sunlight into electricity)" (explains the term photovoltaic—if it must be included). RCraig09 (talk) 14:56, 15 October 2023 (UTC)[reply]
This is a title only, which should be short and precise. The expression in brackets is superfluous and redundant. In terminology, there is the so called substitution principle: you may substitute any kind of term with its definition. No, there is no need to be included at all, as a PV panel consists of a several cells and that is clearly defined as a device in which the photovoltaic effect is utilized [3]. A title of a figure is only for identification what's in the graph, you don't want to repeat the whole content of any scientific paper about PV in the title and you don't wnat to repeat redundant information which is mentioned in an encyclopedia either. A title should be as small (= short and precise) as possible. There is no need to add redundant information if there is no danger that PV could be misunderstand. There is only one interpretation of photovoltaic panels which relates to the photoelectric effect in which an electric potential difference is produced between two points in a material by the absorption of photons [4].
Here is a second point: the naming of the x-axis as "Installed capacity (cumulative)". Why not just saying "Installed cumulative capacity" which is much easier to read? Else is sounds like a military notation, similar to reverse Polish notation, where you have the main noun first followed by the characteristics in order of importance (e.g. belt, leather, black). This is fine for sorting a list of items, but not natural language use. --Gunnar (talk) 08:41, 22 October 2023 (UTC)[reply]
All of your comments overlook the fact that most readers of a layman's encyclopedia do not understand the meaning of photovoltaic (see Google search results and Google Trends search term data, above). Photovoltaic is jargon. See MOS:JARGON. The phrase "(convert sunlight into electricity)" is not "superfluous and redundant" to the lay reader as you claim; the phrase is necessary for the reader's understanding of jargon. I compromised to include photovoltaic in the first place, but since photovoltaic is included it must be explained so that its meaning is readily understood by the lay reader without forcing him to go to another article that isn't even wikilinked. Here, a title is not "only for identification" as you claim; the title is for clarification and explanation of jargon. An article in a layman's encyclopedia is not the "scientific paper" you refer to. All of your 08:41 comments are formal, not substantive, and I intend no further changes. RCraig09 (talk) 14:36, 22 October 2023 (UTC)[reply]
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