http://grilltip.blogspot.com/2015/06/tips-for-grilling-on-go-this-summer.html

Fill 'er Up: Make sure to bring enough propane or charcoal to keep the fires burning for your entire trip. On average, a 20-lb. propane tank will last for approximately 12-14 hours-but you'll need an adapter hose to attach it to a portable gas grill. A smaller, easy-to-tote 1-lb. tank will last for approximately an hour and a half, so make sure to plan your meals and pack accordingly. For charcoal grills, you'll need about 50 briquettes to fuel a standard stand-up charcoal kettle-so plan to use 30 briquettes each time you grill for a compact model, like a Smokey Joe.