I don't think this is the full context for CA's rolling blackouts, although it's true that the Navajo Generating Station did sell to California.

The California rolling blackouts were back in the summer, when solar energy production is highest. If reliance on solar were the whole story, those blackouts would have gotten worse and worse from summer through fall and winter. Instead, they only lasted a total of about three hours over two days.

https://www.latimes.com/environment/story/2020-10-06/califor...

> Officials have consistently said that intermittent power sources such as solar panels and wind turbines didn’t cause the rolling blackouts.

> Energy providers collectively under-scheduled the amount of electricity they expected to need. That allowed power plant operators to sell their juice to customers in other states, resulting in thousands of megawatts being exported even as the Independent System Operator warned that rolling blackouts were imminent.

But "officials" turned out to be wrong. Intermittent power sources did cause the rolling blackouts — though they weren't alone.

https://www.utilitydive.com/news/california-releases-final-r...

http://www.caiso.com/Documents/Final-Root-Cause-Analysis-Mid...

> the three major causal factors contributing to the August outages were related to extreme
weather conditions, resource adequacy and planning processes, and market
practices. In summary, these factors were the following:

> 1. The climate change-induced extreme heat wave across the western United States resulted in demand for electricity exceeding existing electricity resource adequacy (RA) and planning targets.

> 2. In transitioning to a reliable, clean, and affordable resource mix, resource planning targets have not kept pace to ensure sufficient resources that can be relied upon to meet demand in the early evening hours. This made balancing demand and supply more challenging during the extreme heat wave.

> 3. Some practices in the day-ahead energy market exacerbated the supply challenges under highly stressed conditions.

If I'm reading this report right, the immediately precipitating event was that the Blythe Energy Center, a gas plant, went down, so when solar generation had declined enough at 18:38 on August 14, there wasn't enough reserve power, so they started rolling blackouts on half a million people until 20:38, when solar generation was just about at 0.

Then, the next day, storm clouds and lowered winds reduced the power generation available throughout the peak-usage afternoon hours, until the CAISO scheduling coordinator erroneously ordered the Panoche Energy Center (another gas plant) to ramp down generation. So at 18:28 they started rolling blackouts, which lasted 20 minutes until 18:48.

The Governor appealing to people to conserve electric power, and no more big gas generating stations failing, allowed them to avoid rolling blackouts in the following days.

So it sounds like they need more batteries. Two more hours of batteries would have been sufficient in this case (for about 5% of their 45 GW load, about 2500 MW: 5000 MWh, or 16 TJ in SI units), but ultimately you'll need a few days of batteries, over a million MWh for California, about 3 or 4 PJ. (Pessimistically assuming there's no demand response or other storage.)

At the US$111/kWh cost for lithium-ion batteries cited in https://dercuano.github.io/notes/energy-storage-efficiency.h... this means about they would have needed US$555M in batteries in this case, or probably about a billion dollars for the whole facility, and a million MWh of batteries to move California entirely to solar would of course be US$111B of batteries, which could be invested US$11B per year over the next ten years. This is a significant investment, but hardly unaffordable — PG&E, for example, has about US$17B in yearly revenues, and Southern California Edison US$12M, so even the financial savings from switching to cheaper solar energy are likely enough to pay for storage. Presumably as battery prices come down these numbers will shrink further, and there will probably be substantial demand response due to the residential TOU migration described at greater length below.

Part of the problem is that their planning process was structured around peak demand, which is the hardest thing to handle with baseload-type plants like coal and nuclear; but, in this case they handled peak demand fine, even in the face of higher-than-usual loads! The problem was after the peak-demand hour: demand declined, but solar generation declined even faster, which was a thing they hadn't taken into account in capacity planning!

Another aspect of the problem was that the gas plants they were relying on for peaking couldn't operate at their normal capacity at such high outdoor temperatures, so the very heat wave they were struggling to survive in was also impairing their generation capacity.

With respect to the potential impact of things like the Navajo Generating Station and the San Juan Generating Plant, they California's imports were limited not by available generation capacity but by available transmission capacity:

> The imports category includes both non-resource-specific resources as well as resource-
specific imports like those from Hoover Dam and Palo Verde Nuclear Generating
Station. Total import bids received in the day-ahead market were between 2,600 MW
and 3,400 MW (40-50%) higher than the August shown RA requirements from imports.
Despite this robust level of import bids, transmission constraints ultimately limited the
amount of physical transfer capability into the CAISO footprint.

So, for the reduction in coal generation in New Mexico or Arizona specifically to be a causative factor in California's blackouts, someone would have had to build more transmission lines from Arizona. But the transition to renewables in general, that was a causative factor.

(However, it's not entirely clear to me that all the transmission lines were operating at capacity — they emphasize the California–Oregon lines.)

One of the big things they're doing in response is moving residential customers to time-of-use rates, which means that they'll be able to save money on your electrical bill by using energy during the day instead of at night. That should make it possible to sell appliances that save money by, for example, freezing ice during the day and using it for cooling in the afternoon and at night.

It's hard to tell through the insane level of CYA bureaucratese in this report but it looks like they're also installing more battery capacity.