Considering all of the car still on the road gas furnaces and stoves still in houses that need to be replaced all of the other pesky smaller sources of carbon emissions going to zero is going to be a pain in the ass, the last 10 or 20% being the most annoying of all so you're going to need something. Meanwhile we're already throwing away solar and wind power in excess of what we can do anything with, and we could easily end up with cheap enough solar that for about 8 hours a day there's literally unlimited free energy you could dump into something like this