What will I need in an inverter for powering my laptop when shoreline power is not available-100/150/200 watt? I'm connected via Verizon wireless. Beyond my laptop how can I determine whether I can handle any appliance using an inverter and the accessory plug. Is it as simple as the appliance says 60 watts on the back and therefore if have a 150 watt inverter I could add another 90 watt appliance to the second inverter plug and still be okay. Hope my question is reasonably clear!