I tested the $300 Panasonic NN-SD997S with inverter technology against three other countertop microwaves: the $290 Sharp Convection Grill R-820JS, the $279 Whirlpool WMC50522AS, and the $219 Amana AMC2166AS. As the most expensive of the four models, it was the microwave to beat.
To test it, I popped popcorn, baked potatoes, heated lasagna and macaroni-and-cheese frozen dinners, reheated pizza, defrosted chicken, boiled water, cooked burgers, and made omelets -- all in this microwave. It also means I endured a lot of taste tests (with varying levels of deliciousness) to deliver you a comprehensive review. You're welcome.
For the most part, I am really happy with this microwave. It looks sleek and professional and it's a good deal -- $300 for 2.2 cubic feet of capacity and 1,250 watts. You're definitely getting a powerful, capable appliance for a midrange countertop price. The inverter technology and sensor modes disappointed on occasion, but I'm going to make a bold statement about microwave functionality: every single model is going to require some trial and error; the tech for flawless moisture sensors and perfect default settings just isn't there yet. Fortunately, this particular model didn't require much tweaking, so I consider that a relative success.
This Panasonic would be best suited for someone who regularly cooks large quantities of food in their microwave. It will take up a lot of countertop space, or a lot of cabinet space if you want to buy the $180 accessory kit and turn it into a built-in model. If you're on the hunt for a midrange appliance that performs well and masquerades quite effectively as a higher-end product, you may have just met your match.
Let's talk design and usability
This large, 2.2-cubic-foot microwave weighs 36.8 pounds and its external measurements come in at approximately 14 inches high, 24 inches wide, and 20 inches deep. It's decked out in a stainless steel finish and the display screen and dial are illuminated with blue LEDs; my fellow review editors and I unanimously agreed that this was the best looking of the four microwaves. The entire instrument panel is extremely intuitive, especially for a model offering advanced features that have the potential to muddle an otherwise straightforward display. There's even a menu option that provides step-by-step cooking instructions in three different languages if you need more assistance.
You can plug this versatile microwave into an outlet and situate it on a countertop or you can spend an extra $180 on the optional built-in kit for custom installations. Just make sure to bring along a plate from home when you're comparing models in person to see which internal capacity suits your needs. This Panasonic's 2.2 cubic feet is on the extra large side, so you might not need all that space. If not, some of the other models we're reviewing have smaller internal capacities and will likely take up less space on your counter. The Amana, for example, got high marks for performance and has an internal capacity of 1.6 cubic feet.
What about features?
The most uncommon feature on this microwave is its inverter technology. Inverter technology makes lofty claims that it can cook delicate foods like eggs and fish more evenly than traditional microwave heating tech. That's because most microwaves operating on 50 percent power switch off and on between 100 percent and 0 percent power to achieve that 50 percent average. Instead, the inverter tech maintains the low power level throughout the cooking process. Supposedly, this makes all the difference.
Sensor technology is another feature offered on this microwave. It uses a moisture sensor to determine the status of your food. There's no need to input a timer, you just select a specific sensor category and hit "start." Sensor cooking on this microwave can make oatmeal, breakfast sausage, omelet, soup, frozen entrees, frozen pizza (single-serving), frozen pocket sandwiches, potatoes, fresh vegetables, frozen vegetables, canned vegetables, white rice, brown rice, frozen dinners (which seems unnecessary since the frozen entree sensor covers the same weight range), pasta, stew, ground meat, and fish fillets. It also has a sensor reheat function.
How did it perform?
Because it has a moisture sensor, instead of a preset that always cooks your food for the same amount of time, the Panasonic automatically senses the doneness of whatever you're making. So I tested the sensor's ability to bake potatoes, heat Stouffer's frozen lasagna and macaroni and cheese, reheat pizza, and defrost chicken. I also tested how quickly this model could boil 1 cup of water, how evenly it could cook a burger, and how well it could make a two-egg omelet as per Panasonic's own inverter technology recipe. Let's see how it did.
The one preset that isn't sensor-controlled is the popcorn mode. You just press the popcorn button; it defaults to 3.5 ounces and it pops for about 2 minutes and 20 seconds. The average number of kernels per bag is 448, and the first test returned 97 unpopped kernels (21.65 percent), the second test returned 73 unpopped kernels (16.29 percent), and the third test returned 69 unpopped kernels (15.4 percent). The more kernels it popped, the more burnt pieces it produced. So, really, the first test with 96 unpopped kernels made the best popped popcorn.
Overall, the Amana performed the best. It had fewer unpopped kernels and no charred pieces. The Whirlpool had more unpopped kernels than the Panasonic, but no burnt pieces, and the Sharp performed extremely poorly on its default setting, yielding considerably more unpopped kernels than popped. Overall, I was happy with the Panasonic's default and its performance.
I used the baked-potato sensor mode for this test. For each of the three tests, the sensor cooked the potato to near perfection (for a microwaved potato). The potatoes clocked in at 12.05, 14.65, and 12.65 ounces and the sensor adjusted accordingly. The first test took under 8 minutes, the second 9:02, and the third, 8:08. It performed extremely well, producing soft, evenly cooked potatoes every time. The Whirlpool also had consistently good potatoes with the added bonus of crispy skin. The Amana produced decent results, but the potato preset defaults to an average weight of 10 ounces. Unless you use a 10-ounce potato every time, you're going to get inconsistent results. The Sharp potato preset yielded undercooked potatoes for all three tests.
I used a 10.5-ounce single-serving Stouffer's frozen lasagna meal for the first test, and 19-ounce double-serving Stouffer's frozen lasagna meals for the second two tests. Using the sensor function, the first test took 7 minutes, 59 seconds. It was very well cooked and tasted great. The second test cooked for 11:23 and needed a full three additional minutes to reach 160 degrees (food safety regulations stipulate that the internal temperature should reach 160 degrees before you eat it). For the third test, I deviated from the sensor testing and tried the box instructions (about 14.5 minutes). That worked a lot better than the second test.
The sensor performed extremely well for the smaller frozen lasagna meal, but not as well for the 19-ounce double-serving meal. This tells me that the sensor isn't perfect and some trial and error on your part will be necessary. Regardless, it still performed extremely well compared with the Sharp, Whirlpool, and Amana microwaves.
Frozen mac and cheese
I used three identical 12-ounce single-serving Stouffer's macaroni and cheese dinners to test the sensor's frozen dinner function. Oddly, the first test cooked for 7:45, the second for 8:32, and the third for 7:27. While all three of the results hovered around done, the second was slightly overcooked and the third was slightly undercooked and actually needed an additional 30 seconds.
This tells me that the sensor works pretty well, but that you still need to check the temperature of your food before eating it. Microwave technology has moved pretty slowly, and even when a sensor gets close, it still might not reach that 160-degree minimum.