Most of my 18V Ryobi packs spend their days on a shelf, fully charged and waiting for a drill I might not touch for weeks. That stored energy has real value when the grid drops, and I've already covered how tool batteries hold up in a blackout. Getting the most from them comes down to the adapter. A USB adapter handles phones and tablets, a clip-on inverter supplies a true 120V outlet, and a 12V step-down adapter feeds gear that runs on DC. The runtime math is simple: multiply volts by amp hours. An 18V 6.0Ah pack stores about 108Wh, and a 4.0Ah pack stores about 72Wh, before conversion losses take their share.