The lifespan of a 12V battery when powering devices through an inverter varies greatly, but generally, you can expect anywhere from a few hours to over a day depending on the battery's capacity, the inverter's efficiency, and the load it's supporting. A 12V battery lasts based on the appliance and its power consumption. However, actual performance varies. They can transform your 12v battery, typically found in cars, into a portable power source, letting you enjoy some of the conveniences of home even off the grid. Finally, multiply run time hours by 95% to account for inverter losses.