I use a Bitaxe Gamma connected to a Jackery Explorer 300 that rarely gets used (maybe once or twice a year) and the Jackery is powered/recharged by a 100w solar panel. It mines Bitcoin through Braiins Pool with Lightning payouts to my Speed Wallet. It is slow, but doesn't cost anything to power. The Bitaxe uses about 21-25w with rest of the wattage charging the Jackey. It'll run overnight and start charging in the morning on a full sunny day.