What's a well-designed gas grill? Unfortunately, there's no magic formula. In general, such grills have at least three or four burners, with 12,000 to 15,000 BTUs per burner. In the best of all possible worlds, they come with heavy cast iron or rod stainless steel grates, which produce handsome, well-defined grill marks. Ideally, they'll have easy to empty grease catchers and rotisseries with separate burners.
But much the way a four-cylinder sports car can out-perform an eight-cylinder SUV, the overall performance is more a function of design than numbers and the best way to pick a gas grill is to see it in action. Ideally, when you preheat it to high, you'll reach temperatures of 700 to 800 degrees. One way you can boost the performance of a moderately priced gas grill is to preheat it the time recommended by the manufacturer, then continue preheating it another 10 or 15 minutes while you drink more beer.