There are many reasons to own a generator, but how you plan to use it determines the size —meaning the amount of power—and type you need. Adding up the running watts and the highest starting wattage of all the devices you wish to power with a generator will help you determine the size of the generator you will need. As we mentioned, most appliances, like lights, TVs, laptops, and small appliances, run on 110-120 volts. If you need to power 240-volt devices, you’ll need a generator and connection equipment that facilitates it. You will most often see watt-hours listed as the “capacity” of a battery-based generator (i.e., power station or solar generator).