Dirty production initiates based on demand. So-called “peaker plants” start up under high demand when cost per megawatt rises. They typically start early in the day as most people wake up and cook breakfast and get ready for work and then shut down after people get home and wind down for bed. More extreme versions of this only fire up for more extreme weather events or when other plants trip offline unexpectedly. If demand is normalized, so too is production, which would phase out dirtier power production like coal and natural gas. As an operator at a combined cycle natural gas power plant, this would force me to find a new job. Which is fine by me. The system needs to be changed to be fixed, even if it causes a little pain for me.
Think of the grid as a pressurized system. To maintain consistent pressure, demand and supply need to be approximately equivalent. When use is high, the pressure drops so demand goes up to maintain that pressure, so prices per megawatt rise to incentivize power plants to step on the gas pedal to produce more. When use drops off, that production needs to reduce to prevent over pressurization of the grid. With battery storage, that pressure swing diminishes. It’s effectively a pressure regulator.
Additionally, the home power management system via UPS and inverters does exactly what you’re saying in terms of using it when it’s available. At times of high demand and high cost and low supply, your home could seamlessly switch over to your home battery supply for your energy needs to remove strain on the grid, and this would be attractive to set up through things like proposed tax credits and generally reducing your home energy bill. So at 3pm in an August heat wave, your AC could be battery powered from when you charged while you slept the night before. And you’ll recharge tonight when everybody’s AC has switched off for the most part. All this to say: you’re absolutely right and we already agree, but also we can use emerging tech and legislation to vastly expedite this badly-needed transition.