Comment by dvh
This summer I've made indoor (no direct sunlight) solar powered kitchen timer and I used STM32L011, it's winter and it's still working and voltage is stable. The power consumption is 100-150uA (28uA for display, 80uA for mcu, the rest is 1.2-to-3V boost). But it's only on when I cook (maybe 1h a day).
Very cool. Though it's unfortunate that most DIY electronics projects end up looking like IEDs, mine included