The amount of energy your electronics consume will indicate how powerful of a generator you'll need. For example, a laptop will consume about 60-70 watts per hour, whereas a typical space heater will use about 1,500 watts per hour. Needless to say, if you're only trying to charge your phone and laptop, you won't need anything too fancy. However, if you're trying to heat your tent, you'll want a generator that's a little more robust.