The holiday cooking season coming right up, and that means you’re oven is about to get a real workout. But 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.”
The Truth About Your Oven’s Heating Cycle
Not every oven is created equally as far as accuracy is concerned and oven temperature accuracy can drift over time. In fact, most ovens are off their set point by about 25-50°F. For example, if your oven is set to 325°F (163°C), but averaging a higher temperature of 360°F (182°C) at that setting, your cooking results will be off the mark.
Ovens have thermostats that trigger a heating cycle to keep the internal temperature near the set temperature. 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.
The ChefAlarm®, with the optional Air Probe and Grate clip, is the perfect tool for testing your oven’s accuracy. 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 temperature oscillation and that information can be used to find the accuracy of your oven’s setting vs what it is actually doing.
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.
How to Test Your Oven’s Accuracy
Follow these easy steps to test your oven’s accuracy with a ChefAlarm:
- Start with your oven off completely.
- Set an oven rack to the oven’s center position and attach the grate clip to the middle of the cooking rack.
- Attach an air probe to the middle of the cooking rack with a grate clip (Pro Series® Air Probes work best, but your standard ChefAlarm probe can work as well).
- Set the High Alarm to 350°F (177°C).
- Start the count-up mode on your ChefAlarm by tapping the “Timer Start/Stop” button. (This will tell you how long it takes your oven to preheat.)
- Set the oven to 350°F (177°C) and close the door. Do NOT open the door while the test is running!
- When the alarm sounds, you can silence it by tapping the “Alarm On/Off” button. (If the alarm doesn’t sound for a full 20 minutes, that means your oven is running cool. Skip this step, and proceed as usual.)
- Clear the recorded Min/Max temperatures by holding down the “Clear” button.
- Set your timer for 30 minutes using the Up Arrow button, tap “Timer Start/Stop” to start the count-down mode, and wait.
- When the timer sounds after 30 minutes, note the Max and Min temperatures shown in the upper left-hand corner of your ChefAlarm. This shows you how much oscillation your oven manifests while stabilizing around your target temperature.
- Clear the Min/Max readings by holding down the “Clear” button again and set another 30 minutes on your ChefAlarm timer.
- After the second half hour (when your ChefAlarm timer sounds a second time) note this second set of Max/Min temperatures on your notepad, as well. This second set of temperatures will give you a better sense of the performance of your oven over time.
- Take the average of the second two numbers to see what the average temperature of your oven is at that set point. (For example, if your second set of temperatures yielded a Max of 378°F [192°C] and a Min of 354°F [179°C], your average oven temperature when your oven is set to 350°F [177°C] is actually 366°F [186°C].)
- The difference between this number and the original setting is your “offset.” (In our example, your oven would have a 16°F [9°C] offset—the difference between 366°F [186°C] and 350°F [177°C]).
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.
If your oven is not easily calibrated, use the offset temperature you calculated to manually adjust your oven settings. (For example, a 16°F [9°C] offset would mean that if the recipe calls for 350°F [179°C] , you should set your oven to 334°F [168°C].)
- The same offset should hold true for higher and lower temperatures since the error is in the thermostat. But to be completely sure, you could perform this same calibration test at different set temperatures—every 100°F (38°C), for example.
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.