Grilling with Gas, Grilling with Charcoal

July is National Grilling Month, and that’s a special time for ThermoWorks because we love grilling! We think you probably do too, but that doesn’t mean you don’t have questions about it, and this post is going to try to answer some of them.

Among the most common questions that come up when it comes to grilling are questions of grill type. Gas? Charcoal? Egg shape or kettle? Are they really that different? To answer these questions, we didn’t go to manufacturer’s websites, we got out our trusty high-temp ceramic type-K probes with the extended range fro -58 to 2200°F (-50 to 1204°C) and our Thermadata^® loggers and started taking data. Below we’ve compiled a thermal profile for several types of grills and a smoker so that you can better understand what to expect from—and how to set up—your grill this summer!

Grill types

Most grills can be broken into two major families: those that are fueled by gas of some kind (natural gas or propane), or those that are fueled by charcoal. Within those two families, things break down further. Gas grills can come in all shapes and sizes, and for that reason are great for cooking for large groups. Charcoal grills are often a little smaller, but no less popular! The kettle type and ceramic egg (kamado) type lead the charcoal pack, with dozens of variations on those two themes.

Below, we’ll discuss some of the thermal characteristics of these grills, but we will not be going into specifics on grill brands or models. These are general principles that will hopefully help you become a master of your own grill.

To learn about the heat profiles of each grill type, we used high-heat probes at grill level and two inches above grill level, taking data for each cooking environment. We also used a thermal imaging camera to help us understand the environments better. Sadly, that camera only has a heat range up to 626°F (330°C), so we couldn’t really show the full range of temperatures in many of the grills. (Fire is usually in the range of 1200°F [649°C].) But the relative temperatures across the grill surfaces are still relevant and instructive.

Gas grill heat profile

The internet is full of questions about cooking with gas grills, and it might be because gas grills are the first grill that many—though not all!—people use. The ease of dial-controlled temperature is an appealing feature for many cooks. To see how the actual heat of these grills performed, we heated our natural-gas grill to high heat on the left side, leaving the right side turned off as if we were preparing for a reverse sear or two-stage cooking. Probes were placed over the flame and in the “cool” zone. The grill grate in this particular grill was 2″ from the surface of the  “flavor bar” heat plates suspended above the flames themselves.

You can see in the graph above that the grill surface on the hot side remains hot enough to sear food throughout the cook, while the air just above the surface does not. Two-stage cooking using the cool side will only work with the lid closed, as the 110°F (49°C) that you can get with the lid open is not sufficient to cook anything at all.

When the lid is closed, the ambient temperature for the grill-roasting side jumps into the 325–400°F (163–204°C) range, great for two-stage cooking and cooking things more slowly than over the hot fire of the direct-cooking side. Even with the lid closed, the two-zone cooking differential is still apparent in the thermal image: 

Kettle grill heat profile

The kettle is the most iconic grill in America and with good reason. It’s easy to transport and it is easily customizable. But how does it look, thermally speaking? We started a single layer of coals and distributed them across the charcoal grate, then put probes at grate level and 2″ above. We started with the lid on, then with the lid off, then with the coals moved to one side for indirect cooking with the lid on. The grill grate in this grill was 3.5″ above the surface of the single layer of coals. Take a look at the data:

You can see the intense heat of the charcoal in this graph. With the lid on, the temperatures above the coals soar into the 600–650°F (316–343°C) range. If you want real searing heat for your meat, this it is! In fact, that approached the range that many wood-fired pizza ovens burn at, and is why grilled pizzas work so well on a kettle grill.

With the lid off, temperatures become subject to breezes and the chunky nature of the fuel itself. They hover in the 200°F (93°C) range. If you try to cook with the lid off on a kettle grill, it will take quite a while. Moving the coals to one side and recording the temperature data on the other side shows a perfect grill-roasting temperature around 350°F (177°C). The temp in our cook trails off a bit there because we’d expended a lot of fuel with the lid off. Keeping the lid on is much more energy efficient, as you get higher temps for far longer!

Ceramic egg style grill heat profile

Though a relative newcomer to the American grilling scene, these ceramic eggs have acquired a devoted following. They are famous for steady heat, due to their thick ceramic walls. We set up the diffuser plate for this cook, as one would for indirect cooking, with the lid closed. (We are aware that these grills can achieve much higher temperatures without the diffuser plate!) The data shows that the reputation for consistency is well earned. The temperature curve for this cooker was exceptionally flat, and right in the perfect range for grill-roasting. Interestingly, the sensor at the surface of the grill was cooler than that 2″ above the surface. This is most likely because of the convection currents within the cooker, carrying the hotter air up around the sides of the diffuser, making the air hotter higher up than at grill level.

But perhaps the most interesting feature here is the effect that the legs of the diffuser have on the temperature profile.

The diffuser legs create a shield against the scorching heat of the charcoal, which means that if you are careful, you can use a leave-in probe with this cooker! If you make sure your probe cable lies along the path created by the diffuser, it can be safe from the extreme temps that otherwise would short-out its components. Take the diffuser out, though, and your probe wires are likely to get fried!

Pellet smoker heat profile

This is not, strictly speaking, a grill, but rather a smoker with grill-like characteristics. Some of these smokers claim to be able to sear your food as well as smoke it, which would be great for things like reverse searing a tri-tip. To see how well that might work, we set one to 250°F (121°C) on the controller with the lid closed, then turned the heat to “high,” which the display said was 450°F (232°C). We also ran it at searing temp with the lid open to see if what the temperatures would be like at the surface and 2″ above it. 

You can see the cyclical nature of the thermostat turning on and off in the initial section. You can also see that while the smoker does reach the 450°F (232°C) needed for a sear, it takes about 15 minutes to get there from the smoking temperature. However, the cyclical on-off evens out at that temperature. The right side (away from the pellet box) ran hotter than the left side which is right by the pellet box. Opening the lid caused a steep temperature drop, but managed to maintain something in the realm of a smoking temperature—just don’t think that you can sear with the lid open.

This thermal image of the smoker shows that there are hotspots, just like in any other cooker. The plate under the grate acts as a diffuser for both heat and smoke in this case, but if your cable were to droop down below the grate, it could be exposed to much higher, possible destructive temperatures. After all, that smoke is coming from fire and fire is too hot for thermometer cables!

Takeaways

Charcoal vs. gas grill: which is hotter?

Charcoal burns hotter than gas. Our probes 3.5″ above the charcoal bed had much higher temperatures than those only 2″ above the gas elements themselves. If you want high, high heat, charcoal is the way to go.

Can I use leave-in probes while grilling?

Using leave-in probes while grilling calls for caution and care. The transitions on our Pro-Series^® probes are rated to 644°F (340°C), and, though the thermal imaging we used only goes up to 626°F (330°C), the heat sources we encountered were well hotter than that. You may recall from our Caveman Steaks post that the charcoal we were cooking in topped out around 1200°F (677°C).

If you are cooking over indirect heat, you can carefully use probes. Make sure they don’t cross any direct-heat zones and try to keep them from laying across grill grates, which can conduct the energy to them far more efficiently than air. Keeping the shortest possible distance from where the probe enters the cooker to the food is helpful: if you string the wire a long distance across the cooker, it’s more likely to sag and come in contact with hot elements of the cooker. A shorter path creates higher tension, keeping the cable up off the grill.

In an egg cooker, guide the cable over the legs of the diffuser, in a kettle approach the food from the side opposite your stack of coals. On a gas grill, keep the thermometer away from the hot side.

(For more on caring for your probes in high-heat environments, see our post about probe safety.)

The best grill for the job

We hope that this data can be of use to you. There is, ultimately, no best grill for everything: it all depends on what you want to cook, how you want to cook it, and how involved with that cooking you want to be. But with our thermal tools and information, you can make that choice with greater confidence.

But what more can we do? Is there an experiment or observation you’d like to see us do with our high-heat probes? Do you have a question about a certain style of grill or smoker that thermometry can answer? If so, let us know in the comments! Temperature matters, and we’re here to help you get the thermal knowledge that you need to make your cooking as good as it can be.

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