The key word is "nameplate", a colorful term implying engraving and rivets:

https://en.wikipedia.org/wiki/Nameplate_capacity

Nuclear power is usually run close to nameplate, continuously, as it this is generally more economical.

That's a bummer. Even though the capacity is still in the same neighborhood as the reactor, the cost is greater because you either need a ton of storage capacity or some nonrenewable backups.

I think that's the problem we ran into here in California. As we've decommissioned nuclear and natty plants we've replaced much of that capacity with wind and solar. Then you end up in the situation we had a week ago: power consumption peaks around 6pm when solar is ebbing. If that happens in conjunction with a period of low winds, there's a very thin margin of error and in some cases you have blackouts.

Apparently no:

https://cleantechnica.com/2020/08/27/no-renewables-did-not-c...

Real grids are much more complicated than you'd think.

Regarding costs of various plants, usually you calculate it as an average per kWh, which is still not quite right as dispatchable is worth more than non-dispatchable. (And yes, you can have renewable dispatchable.) If you compare those figures across technologies and locations, tread carefully, it is really easy to come to the wrong conclusions. For instance, you might be comparing theoretically estimated numbers with (somewhat old) real-world averages.

I don't really know what to make of that article from cleantechnica. It says that renewables weren't the issue. But the head of the CA grid also said that "If the wind hadn’t run out, we would have been OK"[1]. Maybe this is wrong, but the way I interpret that is "When a fossil fuel plant conked out, it was the straw that broke the camel's back. But the reason that a single power plant failure led to blackouts is a heavy dependence on renewables without adequate storage or backups".

[1]: https://www.sacbee.com/news/local/environment/article2451155...

Seems to be more like 40% [1] and it's worth noting that in a lot of geographies you still need full backup for wind farms as the wind speed can drop low across the whole country/continent.

[1] - https://energynumbers.info/uk-offshore-wind-capacity-factors

40% is kind of an average of already installed offshore wind project, some having been installed 10 years ago... In wind project in general we've seen a continuous trend of spectacular increase in capacity factor [1], and 40% capacity factor can be expected from a US onshore wind project now... 60% average seems high right now (not in the future) and depend on geographies though

Of course managing intermittence is not easy and free, but nobody is talking about a 100% wind-power grid, and the current installations can absorb a fair amount of intermittence with extra investment... And wind and solar are becoming so cheap that you have a lot of space to pay for managing intermittence - that can be using differently the current installations, developing a demand-response market, and doing some thermal and electrical storage...

[1] see for example https://www.eia.gov/electricity/monthly/epm_table_grapher.ph... keeping in mind the average capacity factor include older equipment with low capacity factor... and that offshore wind is "just starting"