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Why Gas Grills Need to Preheat Longer

By Cook's Illustrated Published September 2015

We call for preheating charcoal grills and gas grills for different amounts of time. Why the difference?

We call for preheating charcoal grills for 5 minutes but gas grills for a full 15 minutes. Why the difference? Both types of grills cook food through radiant heat and conductive heat. Radiant heat browns and cooks the portions of food between the bars of the cooking grate; the hot grate cooks food it touches through conductive heat. (Both types of grills also cook food through convection, the transfer of heat through air.) With a charcoal grill, because the hot coals produce an abundance of radiant heat, preheating the grill is simply serving to heat up the walls and cooking grate. But with a gas grill, preheating serves two functions. Gas flames do not produce much radiant heat, so manufacturers place metal bars, ceramic rods, or even lava rocks between the flames and the cooking grate. It takes about 15 minutes for these items to convert the heat of the flames into radiant heat that can both get the grate searing hot and cook food directly. So what happens when you skimp on the time? Our test—toasting bread for 1 minute on gas grills preheated for just 5 and 10 minutes—shows that the results suffer.

PREHEATED 5 MINUTES

PREHEATED 10 MINUTES

PREHEATED 15 MINUTES