It's not really a matter of whether the grids have capacity; the ties themselves can only handle a limited amount of power.

As per ERCOT's status page, both of the high-voltage DC ties between Texas are currently operating at >99% of their rated capacity, and they have been every time I've checked since yesterday. They're not being limited by the availability of power from the other side.

You’re missing the point. Even if the ties had more capacity, the supply of power on the other side of the ties is not there. It’s a two-pronged issue, and you won’t solve the problem by only focusing on one of the prongs.

This is incorrect. MISO, the system to the north and east of TX, has capacity. The DC ties cannot handle it. You can see this by checking the price signals on their page. Right now, the TX hub is about $1,000 but the MS hub is about $60.

https://api.misoenergy.org/MISORTWD/lmpcontourmap.html

MISO does not have the capacity either. Sections of eastern Texas, such as Orange, are under MISO, and they too have been dealing with blackouts due to lack of capacity. Parts of Louisiana under MISO are also being told that they will see blackouts soon.

https://www.klfy.com/local/cleco-rolling-blackouts-to-be-use...

https://www.arkansasbusiness.com/article/134700/lr-based-tra...

Again, just because you have excess power in Missouri does not mean that power can magically transfer hundreds of miles away where it is needed. Energy transfer does not work like that.

It seems highly unlikely that exactly 100% of the capacity of the interconnects is, coincidentally, precisely equal to the amount of excess power available to be fed into the interconnects at the moment. Do you have anything to back up this extraordinary claim?

Did anyone make that claim? No. Go re-read my comment and try again.

Yes, you did. Per the comment you replied to:

> As per ERCOT's status page, both of the high-voltage DC ties between Texas are currently operating at >99% of their rated capacity

So as of that comment, either the amount of power available on the other side was equal to >99% of capacity, or it was greater than capacity.

The situation has changed now and neighboring states have had to drop the amount provided to interconnects, but as of the earlier comment, more interconnects would have helped.

Your turn to try again I suppose

If you browse a few of the ISO pages for other states/regions you'll see a bunch that have excess capacity above their projected peak for the day.

Here's one: https://www.iso-ne.com/

Here's another: http://www.caiso.com/TodaysOutlook/Pages/default.aspx

But there's a limited capacity for Texas to bring in power over just 5 connections, combined with their choice that makes conversion to something compatible with the Texas grid much less efficient.

By isolating & not focusing on compatibility they have made it very difficult to have more robust redundancy in their grid.

Do the other grids publish their generation/demand statistics live? I remember being able to check the CalISO page during the rolling blackouts in California during the summer.

CAISO says it has 10k MW in extra capacity[1].

http://www.caiso.com/TodaysOutlook/Pages/default.aspx

I am in MISO, which roughly runs up the Mississippi River, and borders TX. They have some real-time data available publicly.

https://www.misoenergy.org/markets-and-operations/real-time-...

They have absolutely 0MW capacity that they would be willing to put online to earn millions an hour? Seems unlikely.