For a long time to come. The energy density of fossil fuels is very high (about 50x higher than that of lithium ion batteries), there's a ton of infrastructure for handling and transporting them and a ton of infrastructure for using them.
They get turned into plastics and energy, two things which civilization feeds on voraciously.
It's not just inertia that keeps them going.
It's an immense uphill struggle if you tried to get people to adjust to where transport is less available, and encourage living or working at closer ranges or conversely long range shipping/travel/vacations seen as more of a luxury. Just thinking about it I'm reminded of the outrage that was fabricated/stirred up over "15 minute cities" in the UK where the idea that you'd be able to get to most things you need day-to-day in a 15 minute walk was warped into a scare of state checkpoints, fines and surveillance. Or the retreat from working from home.
It's a huge adjustment from how the past few decades have established expectations, and it'll take a big force to change quickly, similar to covid even though that was short term in hindsight.
> The energy density of fossil fuels is very high (about 50x higher than that of lithium ion batteries)
That doesn't make sense. Batteries are an energy container, they're not energy itself. How can it be compared to a fuel? The direct counterpart to oil or coal is wind or solar radiation itself, batteries are used to amortize the supply and store an excess for emergency use, but otherwise those types of energy just immediately go into powering the grid.
The economic case for renewable power is actually extremely good, because unlike fossil fuels, they're effectively infinite and don't need complex infrastructure to extract. They're free. You only need a power plant that directly converts them into power. If we were just able to shift fossil fuel demand towards producing goods like plastics, this would already be massive. However, a lot of powerful people are deeply invested into fossil fuels and will do anything to tip the scales into their favor, despite gradually losing in the energy sector.
It makes perfect sense to look at energy + container subsystems.
It doesn't make sense to look at that in a vacuum. Energy transport over wire via electricity is much "denser" than transport via liquid or gas.
"It depends" is the correct answer, but the equation is shifting quickly towards solar + electricity.
You're the one looking at it in a vacuum. Engineering is all about looking at it in context and the main context where density of energy is important is in vehicles of all shapes and sizes. That's where the rubber quite literally meets the road. You can then theorize about what the 'weight' of the electrical energy is but it is pointless: the weight of container dwarfs the weight of the energy carriers (effectively the electrons) themselves. In the case of fossil fuels the ratio is more balanced, the container will weigh a couple of kilos and the fuel will way a bit more (say 10:1 or 20:1). So to compare the one with the other we weigh the batteries and ignore the electrons and we then compare that with the fuel because that is the dominant factor.
Solar + electricity are not directly suitable for powering electric vehicles, that's where the batteries come in.
Comparing apples (transport of electricity via wires) with oranges (transport of energy via liquid or gas) misses the elephant in the room: you are not going to be able to use those electrons without a suitable temporary storage medium unless you plan on carrying a very long and impractical extension cord behind your now very light EV.
Why? In the context of the electrical grid, has the amount of storage you can have in the backburner ever been a choke point? If anything, fossil fuel power plants have the very same batteries to buffer some energy. But for the vast majority of power consumers that can just exist on the grid, power storage is nearly irrelevant because it can go directly from producer to consumer. Even in places where storage is relevant (anything that can't be tethered to the grid, like vehicles) the equation is different because the infrastructure you need to convert fuel to power (engines vs electric motors) don't weigh the same. Yes, even with that, pure electricity still falls behind somewhat, but it's getting better. And I was mainly talking about the power grid anyway, with how universal and important it is. Fossil fuel straight up loses in that sector, like what I said before, so replacing it is an easy choice... and yet we don't do that.
The only context in which comparing power densities makes any sense is the vehicular one.