It's all fun and games in the CNET Appliances Test Lab until it's time to bake biscuits. Then, it's science.
Testing the performance of ranges and ovens here at CNET is a mix of balancing the objective data we collect, such as temperature readings, with more subjective observations, like how something tastes. It's impossible to rate the flavor of a burger or the texture of a chicken's skin by simply staring at graphs and charts. Instead, we combine data collection with taste testing to produce a well-rounded review that will let you know if an oven or range is a good investment for your home.
We're always updating and improving our test methodology for oven and range reviews, and you can expect much of what you read below will evolve.
Test environment, equipment and terminology
For the data-gathering portion of our tests, we use the following tools:
Environmental multimeter: We use this device to track ambient temperature and relative humidity during testing. Oven performance isn't as sensitive to environmental variables as that of other large appliances, but we generally like to perform our test at plus or minus 4 degrees Fahrenheit of 75 degrees Fahrenheit (24 degrees Celsius), and plus or minus 15 percent of 45 percent relative humidity.
Wireless multimeter: Our multimeter helps us ensure that the voltage from our power outlets to each oven remains at or above the recommended specification. Falling below spec could result in lower heat output and longer cooking times.
Whole-lab integrated system: We use thermocouples to measure temperatures during testing in ovens and on cooktops. The thermocouples are connected to hardware from National Instruments and custom software we built in-house, which then collects all the temperature data.
Stopwatches: We measure times with standard stopwatches you might see on a basketball court.
A quick note about the appliances: We test both ranges and ovens in the Test Lab. These terms are sometimes used interchangeably, but there is a difference. A range has both a cooktop and an oven (and we test both parts), while an oven is just that.
We're always looking at new ways to test products, but currently we have four tests we perform on each oven. We run each test at least three times on each unit. We'll conduct an additional test run if the results of an individual test fall outside an acceptable margin of variation. If that result is closer to our initial tests, we'll throw out the out-of-range score, and average the three best results. If the follow-up result is still out-of-range, we begin troubleshooting, which can include consulting with the manufacturer if necessary.
We test ovens in traditional bake modes and convection bake modes. Most newer oven models have a convection fan in the back of the oven cavity that circulates heat for more even baking. A convection fan also cooks food faster, so you often have to convert a recipe's temperature. Most convection ovens have an auto-conversion function that dials down the temperature automatically, and we use this feature when available. If an oven doesn't automatically convert the temperature, we follow the widely accepted method of subtracting 25 degrees F (about 15 degrees C) from a recipe's recommended cooking temperature.
We follow the manufacturer's recommendation for what level to place oven racks for baking, roasting and broiling, which can vary from appliance to appliance. We also follow package instructions and use the median recommended baking time when we use canned biscuits for tests.
We first test how well the oven bakes when it has just one rack of food and when it has two racks of food (we refer to them as single and double rack tests, respectively). For the single rack test, we bake a package of Pillsbury Grands Homestyle Buttermilk biscuits for 15 minutes at 350 degrees F (177 degrees C) on traditional mode, i.e. we don't use the convection fan. For the double rack test, we bake 24 Pillsbury Buttermilk biscuits for 9 minutes at 450 degrees F (232 degrees C) on convection mode. Keep in mind that we enable the auto-convert feature when available, which will lower this temperature.
For both single and double rack tests, we set the oven to the appropriate temperature. Then, we remove the biscuits from the refrigerator, where they've been resting for at least 12 hours at 38 degrees F (3 degrees C). For single-rack tests, we place the eight biscuits in the pack of Grands 2 inches apart on an AirBake baking sheet. For the double-rack tests, we fill two baking sheets, each with three rows of four biscuits, with 2 inches of space between each row and column. When the oven notifies us that it has reached the desired temperature, we wait 1 minute before we place the biscuits in the oven.
After the appropriate amount of time has passed for the test, we open the oven door, remove the biscuits onto cooling racks for pictures and turn off the oven. We evaluate the results by looking for even browning across the tops of the biscuits, and taste testing for moistness. After we take pictures of the biscuits, we convert them to color representations to better show the varying levels of brownness.
For our roasting test, we use a whole chicken that weighs about 5.5 pounds (about 2.5 kilograms). We follow this recipe, but only use salt, pepper and olive oil to season the chicken. We truss the chicken, place it on a roasting pan and roast it at 425 degrees F (218 degrees C). We use thermal probes in the chicken's breasts to track the internal temperature of the chicken. The probes are connected to our integrated system so we can track the temperature as it cooks. We remove the chicken from the oven once it has reached 165 degrees F (74 degrees C), the US Food and Drug Administration's recommended minimum temperature for cooking poultry, and record how long it took to reach that temperature. If either probe measures under that, we record the additional time required to hit temperature.
To evaluate an oven's roasting performance, we taste both sides of the chicken, looking for crispy skin, and moist white and dark meat.
We use hamburger patties to test an oven's broiler, a cooking function that applies direct heat to the item that you're cooking, for a straight-from-the-grill flavor. We use ground beef made of 80 percent lean beef and 20 percent fat for these tests. With a kitchen scale, we measure 5.3-ounce (about 150-gram) portions of beef and use a hamburger press to form six patties per test round.
Once the patties are made, we place them in three wire holders that we made in-house (this helps us flip the burgers during our tests) and arrange them in two rows of three on a broil pan. Then we insert thermal probes into the center of each patty to record internal temperature.
We turn on the broiler and use the default setting, then begin recording the voltage usage. We preheat the broiler for 5 minutes, wait an additional minute, then place the broil pan in the oven. We close the door unless an oven's manual recommends open-door broiling. We let the burgers cook for 6 minutes, then flip them. We turn off the broiler and remove the broil pan once each burger patty has reached an internal temperature of 145 degrees F (about 63 degrees C). With the data we collect on our software, we can see how long it took for each patty to cook, which often varies. We also evaluate each burger's interior and exterior in terms of moistness and char.
We use two different tests when evaluating cooktops. The first is a water boil test that we conduct on the cooktop's highest-power burner. We begin by recording the oven voltage, as well as the date, time, burner location and ambient temperature and relative humidity. We fill a 5-quart (4.7-liter) pot with 112 ounces (about 3 kilograms) of water. The starting temperature for the water is is 75 degrees F (24 degrees C), which we obtain with the help of Intellifaucet valves.
We secure a thermocouple to the side of the pot with a bobby pin and put the end into the center of the pot about an inch from the bottom. We turn the burner onto its highest setting and use our system to record how long it takes for the water to reach 209 degrees F (about 98 degrees C), a boil temperature we determined based on our Louisville, Kentucky office's elevation and barometric pressure.
The second cooktop test evaluates an oven's ability to maintain a steady temperature after a longer period. We mix a can of Campbell's Condensed Tomato Soup and a can's worth of water in a 2-quart (1.9-liter) pot. We place the pot on the smallest-powered burner on the cooktop and insert a thermocouple in the pot in the same manner as with the boil-water test. We turn the burner to its medium setting and begin recording the temperature in our integrated system.
Once the soup has reached a temperature of 160 degrees F (about 71 degrees C), we change the burner to its lowest setting and let it cook for 20 minutes, while also recording the temperature in our system. After 20 minutes, we look at the data to determine how much the temperature of the soup varied after the heat was turned down.
Putting it all together
With all of the data we collect, plus the lingering memories of tasty (or terrible) samples, we take a big look at the oven or range we're testing to rate how well the oven performed. We also perform additional anecdotal tests on any special features, such as a pizza oven setting. We score the appliance based on that performance, along with its design, features and usability.