The next best time is today. Fortunately for Wyoming, a new nuclear plant started construction just this year. Kemmerer isn't that far from Casper. https://energycommunities.gov/terrapower-nuclear-plant/

$4 billion for 500MW, or $8 per watt. That's 2-4x the cost per watt of solar.

That's not as bad as I expected, and probably looks even better when you factor in the difference in uptime (e.g. including storage into the cost of solar).

With or without subsidies?

I have no numbers but I've heard lots of times that "green" energy like wind and solar get a lot, and nuclear not so much.

My numbers are price before subsidies.

The government is paying for 50% of the nuclear plant, and there's a 30% write-off on solar.