I am looking to put a raspberry pi to sleep using a uC to save power and to also wake it back up when the uC needs to unload processing requests. Unfortunately, I need an SBC of some sort with this capability as I need to have easy access to OS functionality and the pi looks very appealing due to cost. After some research, the pi does not appear to have power management to support this type of functionality easily.
What are my options for this? If I shut down the pi using the command line while power stays plugged in, will it still draw close to the same amount of power compared to when it is on and not doing a whole lot? Is there anything out there currently that I could connect to GPIO of my uC to cut power after shut down that is inexpensive?
What are all of the things I can do to reduce power consumption of a pi (don't yet know which model I am targetting) both physically and from the command line (I would just run a shutdown script to disable as much as possible)?
Finally, this will be in a PV array application and I expect this to be deployed for upwards of 10-15 years, so every watt counts!
EDIT: It is also important to note that I will be gaining access to the pi via terminal, so I do not need any graphics capability whatsoever.