I don't think it matters (or perhaps I'm not following)? We need to decarbonize the entire energy sector, not only the electrified segment. That presumably means electrifying all of it and powering it with clean energy. Since we're talking about 100% solar in this thread, we'd need a lot of land to do the job.

It matters because it leads you to overestimate the energy needed. It does not take 1 J of renewable energh to replace 1 J of coal.

And it's not just the electricity sector where this matters. A battery vehicle uses much less energy that a gasoline vehicle, because the latter has maybe 25% average thermal efficiency (that varies with details, of course). It applies to any industrial process using anything below arc furnace level heat: heat can be generated by heat pumps (compress argon to the desired temperature, extract the heat, then expand the cooled argon maintaining its temperature with low grade waste heat to recover some of the work.)

About the only place it doesn't apply is if the electricity is used to make synfuels (aviation fuel, for example) or in chemical processes where the fossil fuels were used directly (hydrogen for ammonia synthesis).