> Efficiency has a huge impact on the cost/economics
It doesn't have nearly as much impact as other factors, such as abundance of the material, how easy/practical it is to work with it (which influences both demand and supply), whether mass infrastructure for it already exists (although this is more relevant in the short-term rather than long-term), etc.
These factors impact the economics of an energy source much more than efficiency, and economics is by far the most important factor in deciding whether an energy source will be used or not (and how much of it), not efficiency.
e.g. if hydrogen is only 10% efficient but there's 10 times more of it on Earth compared to a similar energy source that is 90% efficient, then hydrogen wins (all other factors being equal).
As another example, if hydrogen tanks in cars explode 100 times as often as gas tanks, then it would probably be a complete non-starter for powering vehicles, regardless of efficiency.
Which might mean very little compared to the other factors.
3 x 10 cents, which could represent a fixed amount of an abundant and easy-to-work-with energy source (therefore cheap) which has 33% efficiency (hence the 3x cost factor), still costs much less than say, 1 x 5 dollars, which might represent the same amount of energy provided by a scarce and/or hard-to-work-with energy source (therefore expensive), even if this energy source is 99.999% efficient (hence the 1x factor).
As an analogy, let's say you live in a community on an isolated island and you need to eat.
You can satisfy your hunger / nutrient / energy requirements with 1 coconut or with 5 apples (which means we're assuming one apple is only 1/5th as nutritious/efficient as one coconut in this example).
Which fruit serving will be cheaper? You can argue "if you eat apples you will need 5x more of them, therefore they will be more expensive!".
But of course, that might not matter one bit.
The problem is that maybe on the island there might only be 10 (reachable) coconuts but there might be 10,000 reachable apples, so the 5 apples would be much, much cheaper than 1 coconut.
Or perhaps there are also 10,000 coconuts but there are no knives on this island so they would be very hard to open and eat. Therefore you wouldn't be able to find coconuts at the market because nobody would want to pick them and sell them, since nobody would want to buy them despite everybody wanting to eat fruit every day.
It doesn't have nearly as much impact as other factors, such as abundance of the material, how easy/practical it is to work with it (which influences both demand and supply), whether mass infrastructure for it already exists (although this is more relevant in the short-term rather than long-term), etc.
These factors impact the economics of an energy source much more than efficiency, and economics is by far the most important factor in deciding whether an energy source will be used or not (and how much of it), not efficiency.
e.g. if hydrogen is only 10% efficient but there's 10 times more of it on Earth compared to a similar energy source that is 90% efficient, then hydrogen wins (all other factors being equal).
As another example, if hydrogen tanks in cars explode 100 times as often as gas tanks, then it would probably be a complete non-starter for powering vehicles, regardless of efficiency.