In a few weeks, it will be a year since the article “California Just Achieved 95% Renewable Energy.” Will other states come along for the ride? appeared in the Los Angeles Times. Its author, journalist Sammy Roth, had learned that California briefly produced 95% of the electricity consumers used from renewable sources a few days earlier, and he was thrilled. Either he believed or he wanted us to believe that all we had to do was generate 5% more of our energy from wind turbines and solar panels and California would stop emitting greenhouse gases into the atmosphere. . We would achieve something that no other country, city or community in the world had achieved before.
Like the rings of a tree, seasoned energy observers know that a time graph of electricity consumption on a power grid tells a story. All of its curved lines, from moment to moment, are interdependent – when one falls, it can cause another to fall; two others may seem related, but each shape has a role to play. Even though I knew Sammy’s claim wasn’t true, I had to know Why it wasn’t true – why couldn’t it have happened, even for four seconds.
I started by downloading graphs of what happened on April 24, 2021 – precise numbers for supply (production) and demand (consumption), available from the California Independent System Operator (CAISO) website . As you’ll see, it didn’t take much investigation before the monument to solar and wind energy that Roth had erected began to crumble.
The graph below was cobbled together from several others. Some explanations :
- Time moves from left to right. The left side corresponds to 12:00 on April 24, the right corresponds to 12:00 the next morning.
- The blue line at the top shows electrical demand, measured in megawatts (MW) – the amount of energy California consumers were using at each moment of the 24-hour day.
- The other lines below show supply – how CAISO meets demand (at any given time, the heights of all other lines combined are equal to the height of the blue one).
- For four seconds around 2:30 p.m. (red vertical line), California solar and wind power generated 94% more electricity than customers consumed.
- At the same time, however, natural gas plants were producing 3,442 MW and the Diablo Canyon power plant was producing 1,144 MW – with renewables there was too much supply.
- If supply does not precisely match demand on a power grid, it can lead to a system-wide outage. Thus, California had to export 2,489 MW to prevent the grid from failing (dark red line).
- Because Arizona, Nevada, and Oregon didn’t need or want our electricity, we had to pay them to take it (euphemistically called “negative pricing”). This is an expense borne by electricity customers in California.
- During consumption peaks (8:00 p.m.), wind power and hydropower are the only significant renewable resources available. Solar does not provide any electricity.
- At this time, when electricity was the most expensive, California was forced to import more than a quarter of its electricity from other states.
Q: Why do natural gas power plants operate if there is too much renewable electricity?
A: Since solar and wind power are unpredictable, fast-start gas turbines must operate in “spinning reserve” to smooth their output. If a cloud covers the sun above a solar farm, the gas turbines must rev up to make up the shortfall. Or, if the wind suddenly picks up at a large wind farm, they need to slow down to avoid overloading the grid.
Q: So we can’t just feed the grid with solar and wind power?
A: That is correct. Feeding a grid with either requires the natural gas to be ready, to smooth out any sudden changes that might occur.
Q: Why does solar energy flatten out in the middle of the day when the sun is high in the sky?
A: Because solar power would produce too much electricity at midday, system operators are forced to reduce solar power – to instruct operators to shut down their farms. And solar farms are paid to turn off their output — another expense borne by California electricity customers for which they receive nothing of value.
Q: So having “free” solar and wind is more expensive than not? And having renewables on the grid actually forces us to burn more fossil gas?
A: Yes, and yes.
Q: What about batteries? Can’t they fill in the blanks for solar and wind?
A: No. The electricity produced by all grid-wide batteries in California is shown by the yellow line (it hides behind the x-axis of the graph). In order to make a significant contribution to grid electricity, batteries are unnecessary.
California’s nuclear power plant, Diablo Canyon, is set to close permanently in November 2025, to allow investors to build other, more cost-effective ways to generate electricity. Now when they tell you their methods will reduce carbon emissions and you tell them they are wrong, you can tell them why.
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