alt Hacker NewsI believe you need 5v to run the regular $4 pi pico board. The chip only requires 3.2v though so maybe it’s not a hard requirement? There are probably other lighter weight RP2040 boards but I don’t think months or years-long low power usage was an intended goal— it’s $4 (still!) with 40 GPIO pins and PIO and it runs micropython for people scared of/chafed by C— it’s a prototyping/hobby tool.
Pi Pico has a lower power mode that sleeps when not in use that draws well under 5v, but you the programmer have to activate it. I think it is called “lightsleep” but may be wrong.