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Ovens aren't built to hit exact temperatures, and it might affect the way you cook.
You use your oven almost every day, but do you really know how it works? Understanding how your oven heats up and manages its temperature could help you figure out why your brownies are always soggy in the middle, or why your pizza crust is burnt to a crisp, or why your chicken never cooks fast enough.
When you set your oven dial, you’re really setting a thermostat, just like you do when you set the temperature in your living room. If the temperature in the oven is lower than the thermostat setting, a heating element switches on. If it’s higher, it switches off. Sounds simple, right?
The principle is easy to understand, but there are plenty of factors that make real-world performance much more difficult to predict. Your oven dial might be set to 350°F, but it doesn’t perfectly hit and hold the target heat for two main reasons: First, heating elements are binary—they can either be on or off. They aren't designed to hover at specific settings. Second, ovens don’t continuously monitor their own temperatures—it happens periodically, whether it’s every few minutes or seconds. The temperature is in a constant state of flux, overshooting the target and slowly falling beneath it, over and over again—and rarely settling right at the target.
When we analyze an oven's performance, we look at whether the fluctuations averaged the target temperature, and how large the fluctuations strayed from the average temperature. Here's a typical pattern:
Individual results vary, but almost every oven we've tested follows the same general shark-tooth shape.
But what is it that makes most ovens react sluggishly to temperature swings, while a few others are much more precise? Well, ovens haven’t changed much in the past 25 years. Most of them still use a mechanical or electromechanical thermostat, which is basically just a metal rod suspended in a tube of gas. The gas expands as the rod heats, and when it reaches a target temperature, it signals the oven to turn off the heat—or turn back on again when it cools off. Since heat transfer isn’t instantaneous, there’s a period of latency.
Some newer ovens, though, use electronic sensors like thermal resistors and thermocouples, which are more sensitive to temperature changes. This keeps their cooking cavities within a small temperature range—the mark of a consistent and precise oven.
Temperature control is an area where many ovens could stand to improve, but you can start to apply these lessons to your cooking today. Your oven probably spends most of its time at the wrong temperature, so plan accordingly and monitor your food—especially if the cooking time is short, when it's more sensitive to big temperature swings. It all just illustrates the point that the most important part of cooking isn't the tools or the ingredients, but how much attention you pay to your food.