If you’ve had trouble getting your baked goods or roasted meats to turn out according to the recipe, it could be that your oven accuracy is off. A good cook should know their oven well. Are the settings accurate? How stable is the oven after it gets to your setting?
The experts at America’s Test Kitchen say, “Ovens are inaccurate. Since all ovens cycle on and off to maintain temperature, even the best models will periodically deviate from the desired target by at least a few degrees throughout cooking.” “On top of this,” they say, “we’ve found that ovens set to the same temperature can vary by as much as 90 degrees.”
Kitchen ovens use a very simple on/off temperature control scheme. For example, if you set the oven to 350°F, once it gets there (or several degrees past it), the internal thermostat turns the heat off. When the temperature falls somewhere below the 350°F set point, the heat will switch on again. The actual temperature in the oven will “oscillate” or bounce up and down around your setting over the course of several minutes per cycle. The variance between the high and low peaks can be quite large. At a setting of 350°F, the actual peaks might be as high as 400°F and as low as 300°F.
You can monitor this oscillation with the right thermometer and use your knowledge of the oven’s performance to adjust your settings. The highs and lows are important but so is the average. If you set the oven to 350°F, but the center of your oscillation is 330°F, your baked goods will take longer to brown. If the center is higher, say 370°F, the external surfaces will brown more quickly than the insides.
Even expensive ovens with microprocessor controls and digital displays will oscillate and need to be checked for accuracy. Older dial-set ovens may, or may not be accurate, too. Be aware that even an advanced oven that can be switched between convection and traditional heat will actually perform differently between the two methods.
The ChefAlarm from ThermoWorks has a built-in Max/Min feature that can be used to track the high and low peaks in your oven’s oscillation and the information can be used to find the accuracy of the average actual control temperature vs. your setting. Pair the ChefAlarm with the optional Pro-Series High Temp Air Probe which comes with an oven grate clip to easily affix the probe in the center of the oven. Alternatively, you could position the included meat penetration probe with the tip in the oven’s center by using an aluminum foil ball as a stand to hold the probe about an inch above the grate. Make sure the cable avoids touching burners.
Set your oven rack to the center position and attach your probe. Set the High Alarm for 350°F. Set the oven to 350°F and close the door. When the ChefAlarm goes off, silence the audible alarm by hitting any button.
(While pre-heating, you could also clear the Timer function and hit the Timer Start/Stop button to start a Count-Up cycle. When the oven gets to your alarmed set point, stop the Count-Up timer and note the lapsed time. Now you know how long it takes to pre-heat your oven.)
When the alarm alerts you that the oven has hit 350°F, clear the Max/Min registers by holding down the Clear button. Now you can go away and wait for at least 30 minutes. During this time, the Max reading will capture the highest temperature in the oven and the Min reading will capture the lowest reading. Make a note of these on a piece of paper then when the reading is approximately half way between them, clear the registers again. Monitor for another 30 minutes then come back and make another note of the Max and Min temperatures. (You can set the built-in timer for 30 minutes to remind you to come back). DO NOT open the oven door while running these tests.
The second set of Max and Min temperatures provide a very accurate analysis of the oven’s performance. Now you know the spread of the oven’s oscillation. The center of these temperatures is the average temperature of your oven’s actual setting. Whatever difference between this number and the original setting of 350°F can be used as an offset the next time you set your oven. If the actual temperature average is 362°F, the next time you want 350°F you would set the oven to 338°F.
Some ovens can be calibrated to adjust the set point and/or to minimize the oscillation. Consult your oven manufacturer for instructions or call a service technician.
Rather than cooking solely by time and oven setting, ThermoWorks always recommends that most foods should be cooked to a target temperature and that probe-style thermometers like ChefAlarm or DOT be used to track food during cooking. Spot-checking thermometers like Thermapen or ThermoPop should be used to check meats in several places when you’re close to done or to probe baked goods. Nevertheless, it’s still important to know your oven well. ChefAlarm makes this easy.