My google-fu is failing to resurface the links, but IIRC:
One study determined the cheapest energy grids for many countries. IOW, if you had to rebuild the energy grid from scratch today, what would be the cheapest way to meet your needs?
And the answer was 90 - 95% renewables, depending on country. Solar + wind + batteries for 90 - 95% of the power, with natgas peakers for the rest. And that 90-95% number increases every year.
Another survey noted that while Australia and many other equatorial countries are optimal for solar, Finland is pessimal. Most countries have already passed the point where solar is best in pure financial terms. Finland hasn't, but it's very close. Which is insane, given that Finland is a poor place for solar, but a great place for wind, nuclear & geothermal.
One of the reasons I dont expect the australia storage model I cited to be wildly different to, say, Finland is that areas of the world which dont get a lot of sunlight tend to have a lot more wind and hydro potential per capita.
I doubt there are any places in the world where some carbon free combination of solar, wind, hydro, pumped storage, batteries and syngas isnt economic.
Unfortunately, natgas has a large sunk cost advantage. If we were building from scratch in 2025, syngas for the last 2-10% would be competitive. But we have a lot of natgas infrastructure. Syngas's advantage is that it can be locally produced and stored. Natgas has to be shipped large distances, but we already have the infrastructure to do that.
Yeah, if you discount it being zero carbon, syngas is not cost competitive with natgas at all.
https://terraformindustries.com/ is betting the cost crossover point is soon.