I think you have this backwards. This isn't the power company shutting off your power. This is telling your agent (in this case Griddy) to stop buying power under some conditions that you define.
I understand... But in the eyes of the law, Griddy is your power company, and their equipment shutting off your supply might break a lot of laws about disconnecting people without giving the requisite notice, legal procedure, etc.
Where do you draw the line? "Griddy, please turn my power off if the price goes above $1/kwh"... "Griddy, please turn the power off if I forget to pay the bill.", "Griddy, I'll take a $10/month discount if the power gets turned off when my bill is paid late?", "Griddy, I want to use non-ripoff plan, so I'm happy for you to turn my power off the minute I pay late".
See how it isn't really feasible to stop power companies forcibly illegally disconnecting debtors if you allow a debtor to agree to be disconnected voluntarily?
If the property owner has a button to override the cut-off and turn the power back on then that should satisfy any legal requirements related to unilateral disconnection of power. The disconnect should happen on the customer's side anyway. The power company just needs to provide accurate information about the current price in a form that can be used by an automated switch. Important circuits could be placed on a separate panel with a higher cut-off point.
Where do you draw the line? "Griddy, please turn my power off if the price goes above $1/kwh"... "Griddy, please turn the power off if I forget to pay the bill.", "Griddy, I'll take a $10/month discount if the power gets turned off when my bill is paid late?", "Griddy, I want to use non-ripoff plan, so I'm happy for you to turn my power off the minute I pay late".
See how it isn't really feasible to stop power companies forcibly illegally disconnecting debtors if you allow a debtor to agree to be disconnected voluntarily?