You should be asking engineers first, because economists don’t understand energy engineering and what it takes, and won’t be able to build rational models. Also, the future is unpredictable and can’t be modeled - especially when we are way out over our skis and trying something that has never been done before and which will change the world dramatically. Economists aren’t fortune tellers.
And much depends on HOW we get to the fossil-free future. Are we headed for a world filled with abundant energy and wealth due to nuclear power? Or are we headed for a world of lower energy density, rationing, and lower standards of living? Engineering and public choices will decide that - not economists.
Here’s an engineering look at the challenges:
This thread probably belongs in Great Debates, as you aren’t going ro get factual answers about a speculative future.