I do love the idea of microcontrollers for doing random stuff around the house, but one thing I've never figured out is how do you reliably power them in a smal

I do love the idea of microcontrollers for doing random stuff around the house, but one thing I've never figured out is how do you reliably power them in a small footprint, having a switching power supply seems incredibly wasteful for a single ATtiny, and I don't know how long batteries can last.