I think your error comes from thinking all electricity is priced the same for every instant of every day. That is certainly not the case. During periods of high demand, the instantaneous cost to the utility can vary considerably but somewhat predictably. I'm speaking about Arizona here. Thanks to Louis Carrier and his fancy contraption there are a whole bunch of people who can work in the hot country of AZ. Louis' fancy contraptions take electricity, and quite a bit of it. A coincidence of all this, is AC units will tend to run more and thus use more electricity when the sun is shining than they do during periods of no sunshine. Guess what? Solar panels make electricity that will power the solar owner's AC at times and have excess that can be fed back into the grid during these periods of high demand. Electricity prices, during periods of high demand, is much more expensive than it is when demand is low. Excess solar that is being fed back to the grid is only paid at a much lower rate, i.e. my retail price. So with no solar, the utility will be forced to build more or bigger base load plants to serve this peak demand imposed by AC units. Building these plants will cost the utilities money and present yet another problem. Base load plants need to be run at or near their peak and when the demand drops off, it costs the plants money to throttle back and that too, gets factored into the rates. As a consequence, we see off-peak rates offered to encourage consumption during these periods. Something like clothes dryers, water heaters, and ev charging can soak up this extra production and allow the utility to make a few cents / KWH instead of having to pay for not using enough power.
I've linked this before but taking another look will maybe show you how utility scale demand and production fluctuates. https://www.ercot.com/gridmktinfo/dashboards  Pay attention to the bottom right hand window. It gives a picture of how the price of electricity varies over time.