Nuclear had much lower capacity factors in the past, which brings the lifetime capacity factor down. But the relevant point is that the capacity factor of nuclear plants running today is >90%

US Nuclear had a capacity factor of 86.1% as recently as 2012, it just varies through time and over a 40+ year lifetime you don’t have outstanding results every single year. So sure you can argue 71.1% in 1997 no longer applies, but it was almost exactly the same fleet of reactors in use back then.

Yet the person I was replying to said “about 93%” when averaging over 93% has been achieved exactly once in 2019. That kind of nonsense is actively harmful when people hear something and then later realize it’s simply incorrect.

Effective advocacy requires accuracy including technology specific issues and how to mitigate them.

Planned or unplanned is the question.

The larger question is what capacity factors would look like if you tried to double the amount of nuclear as many advocates wish. And what that would do to profitability / the need for subsidies.

Or as the industry has been concerned with for a decade, what happens when renewable energy is regularly sending wholesale prices near zero for hours a day.

Is a 15% difference that much of a different story?

Look at your paycheck, and imagine the number is 15% lower. Should answer the question.

If alternate pay is 90% lower, not big of a difference. i.e. If I lose job, I would prefer new one to pay 85% than 10%.

It does. And no, it's not that significant.

I'm not a nuclear fanboy (well, I wish I made sense since I like the idea of free energy, but renewables are just as good), but I think it's important to make accurate arguments.

An accurate argument would include the financial aspects of +/- 15% in generated output and the impact that has on grid capacity....

With such a small difference, the burden of proof in this case is probably on the person arguing that it is a big difference, since you'd generally expect a roughly linear relationship between these.

In fact, I think I'd suspect that downtime is less relevant for nuclear, since I believe most of it will be schedulable, as opposed to renewables where downtime is random and based on conditions. Since it's schedulable, it could be done in the off season, or different plants could be planned to be out at difference periods.

You actually have no idea about electricity transmission. For long term problems, look no further than France. Short term, look up how electricity generation, transmission, markets and grid stability are linked. Wikipedia is a good start. Followed by studies about 100% renewable grids, those explain why baseload is much less of an issue than people think. And too much inflexible capacity, aka baseload, can actually be a problem itself.

While I'm not a practicing economist, I have a bachelor's degree in economics and took multiple classes on the economics of electricity markets.

While all of those are certainly relevant if you're comparing nuclear and other sources of power, I fail to see how that's relevant to the question of whether there's a significant difference between 80 and 95% capacity factor over a year.

Now imagine you are working in controlling at a power plant operator, and your yearly generated output is 5% lower that whatever plan has before. What do you think would happen?

- investors, management and board saying "no biggy, 5% is not relevant"

- something else

Companies are doing restructuring and mass lay-offs to save less than 5% on bottom line costs, they are incredibly happy when the top line grows by 5% and worried, if not in crisis mode, if the top line declines by 5%. And for the financing part of a new power plant, those 5% are the difference between the investment being a good or a bad one...

Hold on you are an economist and are telling me the difference between a capacity factor of 95 and 85% is not relevant? What do you think the ROIs and margins are for nuclear investments? Considering that nuclear is almost completely dominated by upfront investment, I'd be surprised if the that difference is not the difference between comfortably making a profit on your investment and loosing a large amount of money.