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Comment by moistoreos | Hacker News Reader

Hey bud, do you happen to know when the demand for power is the highest? It happens to be.... gasp.... when the sun is highest in the sky.

Just take a look at ERCOT's website: https://www.ercot.com/gridmktinfo/dashboards/supplyanddemand

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That's just not true. Here's the California grid from yesterday: https://www.gridstatus.io/live/caiso?date=2026-05-09

Peak demand is 6 PM when everyone gets home from work and turns on the air conditioning.

EDIT: Your chart shows the same thing? Demand is highest at 6 pm, not noon.

Ah, yes. California. Where large swathes of costal areas hover between 60ºF and 80ºF. We are talking about Nevada the weather of locality matters and where it can be supremely hot.

You posted the Texas grid, I posted the California grid. Here's the NW grid which includes Nevada. Same thing, demand peaks around 6PM when people get home and turn on their houses.

https://www.eia.gov/electricity/gridmonitor/expanded-view/el...

In France there are 2 peaks in a working day, one around 12:00-13:00, and one around 19:00. On weekends there's a third peak around 22:00-23:00.

https://www.rte-france.com/en/data-publications/eco2mix/elec...

I'm not sure that follows as the biggest driver. 4 PM is nearly as high as as 6 PM. You would expect a big jump at 5 PM, but the biggest jump is from noon to 2 PM. Just looking at today's temperatures on my front porch in Reno, it was 93°F at 2 PM, it peaked at 95°F at 3:30 PM, and it didn't fall back down to 93°F until 5 PM. Some of that sustained power usage probably is people getting home, but a lot of it is A/C.

Unless the graph explicitly states that it includes distributed behind-the-meter solar, then any dip in demand that looks like the inverse of solar is probably grid demand being replaced with local generation on homes and factory roofs or industrial land.

People regularly use the demand being supplied by solar to argue that solar isn't delivering when people need electricity.

The yearly peak grid demand in California is moving later in the day and later in the year due to this effect.

That's the whole point. The OP was lamenting that consumers are getting less for selling their behind-the-meter solar, but if everyone has behind-the-meter solar then that solar is cheap to worthless when the sun is shining. And that's a good thing! The sun is free, all of us utilizing it during the day for free means electricity is cheap during the day. It's when the sun sets and all that solar goes offline and demand rises that electricity gets expensive again.

You said this wasn't true:

> you happen to know when the demand for power is the highest? It happens to be.... gasp.... when the sun is highest in the sky.

But it mostly is.

But yeah if everyone has solar then it's all producing at this time and the very high production can exceed the high demand.

No, the chart you posted clearly shows that in Texas demand for power is highest at around 5-6pm, which is decidedly not when the sun is highest in the sky - it's when the sun is setting and the workday is ending but people are still active and doing things, many of which require electric power - perhaps more electric power than they would use during the workday depending on what the thing is. This is precisely the Duck Curve observation (https://en.wikipedia.org/wiki/Duck_curve) - which was originally coined with respect to the California electricity market but is applicable in many other markets.

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