I would expect the biggest one to be the opportunity cost of what you could have done instead with that electricity besides make fuel. For instance, if, say, c

I would expect the biggest one to be the opportunity cost of what you could have done instead with that electricity besides make fuel. For instance, if, say, converting natural gas heating to electric is a better use of energy in terms of reducing greenhouse gasses, then maybe we should do that first. In the end, a lot of these sorts of proposals depend on cheap renewable energy, and if we can get enough solar and wind power installed then other goals become feasible. Fuel production is an interesting case because you can use surplus energy at times of low demand.