A propane smoker has always asked one thing of its owner. Somebody has to mind the knob. The flame stays the size you set, while the weather changes everything around it.
Masterbuilt’s answer is the ThermoTemp XL, model MB20051316. It is a 40 inch vertical cabinet with a thermostat on the gas. The dial asks for a temperature, not a flame. A sensor inside then turns the burner up or down to hold it.
Without that sensor, this would be just another gas cabinet. So this smoker review asks a single question. Can a gas smoker now be left alone like an electric one? And what does that sensor fail to fix?
First Impressions of the Masterbuilt 40-Inch ThermoTemp XL Propane Smoker
It arrives as a tall black cabinet in two parts. The upper door carries a window over the racks. A shorter lower door closes over the burner, the chip tray and the water bowl.
Underneath, four splayed legs hold a sloping control panel. Wheels on the legs let you roll it across paving. At 92 pounds, you will be glad of them.
Setup is mostly the legs and the regulator hose. Everything else, from racks to chip tray, just slots in by hand.
The panel carries one orange dial, marked 225, 275 and 325 on its face. To its right, an orange push button fires the igniter.
The first cook feels oddly calm for propane. You open the tank, set the dial, press the button and latch both doors.
Smoke rolls from the damper soon after. Through the glass you watch ribs darken without opening anything. A live flame under the chips gives a bolder smoke than an electric element.
Key Features of the Masterbuilt 40-Inch ThermoTemp XL Propane Smoker
Every feature here serves one goal: keep a gas fire steady without you. Some do it with electronics. Others simply keep the food door shut.
- ThermoTemp control. A temperature sensor reads the cabinet and adjusts the burner to match your dial setting. This is the feature you pay for.
- Push-button igniter. One press lights the burner. No match, no long lighter, no crouching at an open firebox.
- Safety shut-off valve. If the flame blows out, the valve cuts the gas to the burner. Nobody watches a burner at three in the morning, so this is no small thing.
- Fuel gauge on the regulator. The Type 1 regulator shows how much propane is left. You learn before bedtime whether the tank will last.
- Four chrome-coated racks, 960 square inches. That figure is the one capacity number Masterbuilt prints the same way everywhere.
- Two doors. The lower door opens onto chips and water. The racks above stay sealed while you feed it.
- Window in the upper door. Bark and colour are visible with the seal intact.
- Removable water bowl and wood chip tray. The bowl adds moisture and catches drips. The chip tray sits over the flame.
- Adjustable damper and locking latch. The damper sets how fast smoke leaves. Closing the latch squeezes the gasket so smoke leaves by the damper, not the seams.
- Tank retention bracket. The cylinder clips upright against the cabinet leg. A bumped hose cannot drag it over.
The capacity claims, though, do not agree. The product page promises room for 16 chickens or 6 turkeys. Masterbuilt’s own dimension artwork says 6 chickens or 4 turkeys. Plan your holiday around the smaller numbers.
On a plain propane cabinet, heat is a guess. You set the valve, then wind, sun and cold meat push the box around. You spend the day nudging the knob.
ThermoTemp hands that job to a sensor. When the box drops, the burner opens up. When it climbs, the burner backs off. On a breezy afternoon that is the difference between watching the dial and leaving it.
Gas also gives this cabinet reach that electrics lack.
Masterbuilt’s page says the dial goes to 375°F. A gallery image of that very dial prints 350°F. Even the lower figure can render chicken skin. Low electric ceilings struggle to do that.
One number is missing entirely. Masterbuilt publishes no burner rating for this smoker. Retailers quote two very different figures, and neither comes from the maker.
That leaves this review with no heat density figure to report. The cabinet also has four stacked racks, not one grate the flame fires through. Dividing a guessed burner by stacked shelves would tell you nothing useful.
What the thermostat cannot do is make the box even from top to bottom. The flame sits low, so the bottom rack runs hottest. Rotate racks once on a long cook, and put the fattiest cut nearest the fire.
The split door quietly makes the sensor’s job easier. Topping up chips through the lower door spills little heat from the racks. The burner then has a small dip to correct, not a cold cabinet to rebuild. Open the big door only to wrap or pull the meat.
Build, handling and durability
The body is steel, black and insulated, in the maker’s words. No gauge or wall build is published. At 92 pounds it does not rock when the door swings. The latch holds the seal firm.
The window is the honest compromise. Glass cannot be insulated the way a steel panel can. Smoke will also film it during long cooks.
Durability rests on three small parts: the sensor, the gas valve and the igniter. A cheaper propane box has none of the three. All of them sit low and outdoors, near grease and rain.
The steel shell will outlast them, given a dry corner. A fitted cover between cooks is cheap protection. So is a habit of closing the tank valve before the dial.
Running costs, upkeep and value
Propane is the only running cost, plus wood chips. With no published burner rating, any figure for cook time per tank would be invention. The regulator’s fuel gauge is your best guide. A spare full tank is sensible before an overnight brisket.
Masterbuilt lists the ThermoTemp XL at $399.99. On September 23, 2026, Amazon had it at $339.99, the same as on October 20.
That gap makes the thermostat easier to justify. A plain propane cabinet asks you to do the sensor’s job yourself. Here a machine does it, for a modest premium.
The saving is really in your day. Without ThermoTemp, a twelve hour cook means checking the dial every hour or so. With it, you check the meat instead.
Upkeep follows the usual vertical smoker routine. When the cabinet is cold, slide out the water bowl and pour off the fat. Empty the ash and spent chips from the tray.
The chrome racks reward gentle cleaning. A soft brush and warm soapy water protect the coating better than steel wool. Give the glass a damp cloth after each cook, while the residue is soft.
Possible Masterbuilt 40-Inch ThermoTemp XL Propane Smoker Complaints
- The thermostat parts get only a year. The sensor and valve are why you paid more. They also sit outdoors near heat and grease. A failure after month twelve comes out of your pocket.
- The maker’s numbers wobble. The top setting appears as 375°F and 350°F. Chicken counts swing from 16 to 6. Trust the 960 square inches, and test the rest on your own patio.
