Solar power has begun to transform the world’s energy system

> ...people are now putting up a gigawatt’s worth of solar panels, the rough equivalent of the power generated by one coal-fired plant, every fifteen hours.

This is amazing! Whether you believe photovoltaics are the most efficient form of green energy production or not, you cannot argue the impressive economics behind them. Successful engineering has to meet the market at the end of the day.

> are the most efficient form

What does this even mean?

being a sentence fragment, not much! It helps to zoom out to the context of the entire sentence, where the GP says: "Whether you believe photovoltaics are the most efficient form of green energy production or not, you cannot argue the impressive economics behind them"

It's definitely impressive that the cost per watt of a PV panel is roughly 13% of where it was just 15 years ago.

https://ourworldindata.org/grapher/solar-pv-prices

You got me. It was a honeypot of a term, "efficiency."

The point is, it depends on how you define it. Engineers may say efficiency is determined by the properties of the photovoltaic cells themselves. Economists may argue it's cost per kilowatt. Politicians may say it's how quickly we can construct solar farms...

You're overstating the current price of PV panels by a factor of three to five; it's closer to 3% of the 15-years-ago price than to 13%. That graph ends in 02023, at US$0.31/Wp, toward the end of the solar-panel bubble set up by the price-fixing cartel at the time. The actual current price is €0.11/Wp, or €0.06/Wp for low-cost (low-efficiency, no-warranty) panels: https://www.solarserver.de/photovoltaik-preis-pv-modul-preis...

€0.11 is 5% of US$2.39 (the Wp price on that graph from 02010), and €0.06 is 2.7% of it. However, my notes from 02016 say that the Solarserver price index for July 02010 was €1.62/Wp; sadly I did not note which module class that was. €0.11 is 6.8% of €1.62, but of course the Euro was worth more at the time...

This three-to-five-fold difference is why you're seeing this article now.

It is, unfortunately, also an apples to oranges comparison. A coal plant actually generates 1GW, 24/7, while "a gigawatt's worth" of solar panels is theoretical peak capacity at noon on a cloudless day.

> It is, unfortunately, also an apples to oranges comparison. A coal plant actually generates 1GW, 24/7, while "a gigawatt's worth" of solar panels is theoretical peak capacity at noon on a cloudless day.

That's incorrect. The capacity factor of a coal plant is between 50% and 60%. That's far away from 100% although better than solar (but not that much better) with capacity factors ranging from 15%-30% [https://en.wikipedia.org/wiki/Capacity_factor].

> A coal plant actually generates 1GW, 24/7, while "a gigawatt's worth" of solar panels is theoretical peak capacity at noon on a cloudless day.

This is called "capacity factor". Other things like maintenance also affect it, no power plant actually generates "24/7". A simple back-of-the-envelope estimate would put solar power's capacity factor at around 25%, so that "gigawatt's worth of solar panels" would generate an average of 250MW. Which is still an impressive number.

So, if I zoom out as you suggest, this means efficient doesn't mean economically efficient. What does it mean here, then? Engineering efficiency? That would make very little sense, since PV and other generating technologies have different inputs. It makes no sense to compare the efficiency of PV modules converting light to electrical energy vs. the efficiency of combustion turbines converting chemical energy to mechanical kinetic energy.

I'm not sure how you're extrapolating your argument from anything that you or I said before. Solar is generally cheaper than fossil fuels for new power generation.

https://www.scientificamerican.com/article/wind-and-solar-en...