Production and consumption are objective. Needs are subjective. The only objective necessity for a living thing is its death — everything else is optional. To think otherwise is wishful thinking.

The behavior of living systems is to expand when not constrained by resources; the human economy has been constrained by fossil fuels for 250 years, due to its inability to take advantage of solar energy, much as it was constrained by agricultural production for the preceding 12000 years, with occasional exceptions like petroleum-drilling-fueled salt refining in the Song dynasty. Since about 02015, solar energy has been brought within within the scope of what the human economy can effectively consume directly, rather than through agriculture.

Very few people have noticed this yet or understand what it means; it's still common to hear foolish remarks like https://news.ycombinator.com/item?id=26220534 "I don't actually see where solar and wind are actually powering a modern economy. I see a lot hope and handwaving." The early stages of exponential growth are indistinguishable from the early stages of sigmoid growth that's an order of magnitude or more from its asymptote; you can't simply extrapolate the growth empirically. You need to understand the underlying dynamics of the system. And so it's very easy to fool yourself, whether out of wishful thinking, vulnerability to manipulation by others, or simple random error. And so far solar energy is under 10% of world electricity generation and under 3% of the IEA's world marketed energy consumption.

So I could be mistaken. Although the solar resource is three orders of magnitude larger than current world marketed energy consumption, maybe there's some limiting factor that will choke off the consumption of solar energy through photovoltaic cells. The most ignorant have suggested that rare-earth metals are such a limiting factor, unaware that solar panels do not use any rare-earth metals. Less absurd is silver: current silicon solar cells use screen-printed silver-paste electrodes, which accounts for some 10% of the cost of the cell and some 10% of world silver mining, so the next order-of-magnitude increase in solar-panel production will probably require the substitution of abundant copper, which will reduce the cells' efficiency.

But the most plausible limitation is storage — a solar power plant is not a direct replacement for a coal power plant unless it's coupled with some kind of utility-scale energy-storage system, which considerably reduces its cost advantage relative to thermal generation stations.

But this is only a limitation insofar as scalable consumers of such intermittent power fail to appear. Traditionally, for example, people would work during the day, leaving their tools idle at night, but this becomes less economically appealing for more capital-intensive forms of production, because they increase the capital cost of leaving your capital goods idle one-third or two-thirds of the time, increasing capital inputs per unit of production by respectively 50% and 200%. Solar-powered industry without enough energy storage to last it through the night and through cloudy days will thus have to pay higher costs of capital per unit of production.

But it seems implausible to me that no profitable and scalable industries exist for which the cost savings from near-zero-cost energy would exceed the cost savings from 24/7 productivity.

So, are there other limiting factors I don't know about?

It may be hard to imagine what humans will use 100 GW or 1000 GW on. But in 01800 it was hard to imagine what we would use 1 GW on (if we don't count agricultural production, which the IEA doesn't). Steam-engines were stationary machines, used mostly to pump water out of mines, and in some cases to drive looms in manufactories; the steam locomotive hadn't been invented yet. Steam-ships had been conclusively shown to be impractical by the disastrous experiments of Papin, Allen, Hulls, Henry, and Fitch; Henry's boat had sunk when he tried to put a steam-engine in it. Fitch's boat at least didn't sink, but his fares couldn't pay the heavy expenses required by the steam-engine. Doctors expressed skepticism about whether the human body could withstand the unbelievable velocities some of the wilder "engineers" were talking about, such as 30 miles per hour or even more. Fulton had met Henry, but hadn't yet seen a steamboat, much less built one. Steam-engines were also notorious for exploding, killing people en masse, and filling their surroundings with poisonous fumes; many doubted their use would ever be widespread.

Yet in 01830 the B&O Railroad was running the 1-kilowatt Tom Thumb steam locomotive down its 23 miles of track (37 km in non-medieval units) at 18 mph (8 m/s) https://en.wikipedia.org/wiki/Baltimore_and_Ohio_Railroad#Ea..., and similar lines were running in England and France. Steam-ships were starting to cross the Atlantic, cutting the transit time to a mere month, and paddle-powered steam-boats plied the Thames, the Seine, the Ohio, the Mississippi, and the Great Lakes. Such is the impact of the advent of a new source of energy.

Remember that in the 01950s von Neumann reprimanded one of his graduate students for writing a compiler, saying that a valuable scientific instrument like the computer should not be wasted on clerical work. What would von Neumann have thought of https://hackaday.com/2021/03/26/nixie-shot-timer-adds-useful..., where a computer runs 16 million instructions per second to detect when a pump has turned on in an espresso machine? Could even such a great mind as von Neumann have imagined such a thing, much less condoned such an irresponsible waste of precious computation?

So we should expect that in 02051 people will be using cheap solar energy for innumerable purposes that today would seem absurdly profligate.

It's also possible that world wars, pandemics, global dictatorships, or other civilization-collapsing events will slow or stop the growth in human use of solar energy. But it seems probable that, barring such calamities, solar energy production will continue to grow until it's a significant percentage of total terrestrial insolation, which is the point at which the plant-shading and heat-retention effects start to become significant.