Generators are usually sized in watts or amps. Appliances without a motor are usually rated in watts or amps as well. Appliances with a motor (such as a refrigerator) will draw more current during motor startup (2 or 3 times as much!) so you need to allow for that.
You can convert watts to amps by using the relationship that W = V x A. For example a 60 watt light bulb at standard 120V household current: 60W = 120V x A so A = 60 / 120 = 1/2 Amp.
Be sure that you use a generator safely by turning it off during refueling and only use them outside in a well ventilated area, because carbon monoxide can silently kill indoors!
When in doubt, consult with a qualified electrician before an emergency strikes. They can install (to code) a transfer box and other equipment to make a permanent generator installation worry-free.
