Have you ever heard of “net metering”?
It means that if your electric company gives you net metering, you can connect a generator or solar panels to your house and sell excess electricity back to the utility at the same price that they bill you for.
Sounds great right?
No, actually its a major problem for the utility.
The reason is that power plants take a significant amount of time to throttle up or down. If everyone in the area has solar power feeding back into the power grid, sudden changes in sunlight can cause major fluctuations and destabilize the power grid.
So what is the solution?
Dynamic pricing. Some areas already do this. How it works is that the price you pay (or receive) for electricity depends on the conditions on the power grid at the moment, updating as fast as possible.
When the grid has a deficit of power at the moment (maybe a power plant is struggling to throttle up to meet demand) the price goes way up.
If the grid has a surplus power at the moment, the price goes down, even going negative.(meaning you must pay to dump your power into the grid, or be paid for consuming excess power)
What this does is create an economic incentive for people to invest in equipment that actually stabilizes and supports the power grid.
For example if you have an electric car charging in your garage, it knows the price of power, and it can start charging faster when the price drops, or it can dump its battery power back into the grid when the price is high. The battery in your car is actually earning money as it sits idle!
Same with solar panels. Even if the installation doesn’t have batteries, the system can choose to stop selling power to the grid when it isn’t wanted.
Likewise, your heated pool can choose to absorb electricity when the price is low.
This is the future of the renewable energy economy in my opinion.
TL,DR: This exists in parts of europe
Doing it in real time like you are suggesting (I think?) would make it hard to adapt to, as many consumers cannot be switched at will (dishwasher, dryer etc.) or needs to keep a certain state (water heater). Also, as far as I can tell none of the common solar inverters can regulate output to the grid (beyond turning off entirely) and batteries are not financially viable yet for most people.
In Norway (and a few other European countries) we have hourly pricing that is set the day before based on projected production and consumption (see: https://en.wikipedia.org/wiki/Nord_Pool). This has the same effect, but makes planning and actually taking action according to the price fluctuations much easier for the customer. More and more companies here are making smart products that can help with this, as well as hobbyists making add-ons for smart home systems to control when power is used. I use Home Assistant and currently have my water heater running the cheapest hours of the day, working on the mini-split and bathroom heat next. When I get my solar install later this summer I'll be moving those loads to use solar as much as possible, with cheapest hours as the backup option if there is no sun. Pretty much exactly what OP wants to achieve, no?
The grid and electricity are also handled by separate companies here, to reduce abuse and exploitation and create competition wherever possible. The grid is owned by municipal companies that have limits set on their yearly income, while the electricity is handled by private companies trading electricity and competing to provide better plans for the customers. Several are offering electricity basically at cost, opting instead to try and make money of smart devices and apps to help their customers spend less on electricity and thus further helping move loads according to prices.
It's all a bit complicated to explain so i hope this makes any sense at all. It's not a perfect system, but it does seem to work and will hopefully only get better as smart home technology catches up.