CNET logo Why You Can Trust CNET

Our expert, award-winning staff selects the products we cover and rigorously researches and tests our top picks. If you buy through our links, we may get a commission. Reviews ethics statement

Panasonic NN-SD997S microwave review: Midprice microwave boasts high-end features

This $300 countertop model employs inverter tech, which claims to cook "delicate foods" like eggs and fish more evenly. But are there less expensive countertop microwaves that can still get the job done?

Megan Wollerton Former Senior Writer/Editor
10 min read

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.


Panasonic NN-SD997S microwave

The Good

The <b>Panasonic NN-SD997S</b>'s impressive internal capacity will feed a large family and the sensor functions generally deliver. Also, its high wattage yields quick results.

The Bad

The inverter technology claims to make "delicate foods" like eggs and fish better than its non-inverter competition. It didn't.

The Bottom Line

If you're interested in the inverter tech angle, you may be disappointed. But if you don't expect to get artisanal omelets from a microwave, it's still a solid choice for a large, midprice countertop model.

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.

Panasonic's NN-SD997S microwave uses inverter technology (pictures)

See all photos

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.

Colin West McDonald/CNET

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.

Colin West McDonald/CNET

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.

Colin West McDonald/CNET

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.


Katie Pilkington/CNET

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.

Ry Crist/CNET

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.

Ry Crist/CNET

Baked potatoes

Ry Crist/CNET

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.

Frozen lasagna

Katie Pilkington/CNET

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

Megan Wollerton/CNET

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.

Reheat pizza

Ry Crist/CNET

I relied on the Panasonic's nifty sensor reheat function to reheat all three slices of pizza. The reheat time hovered around 1:15 for all three tests. While all three slices were definitely heated, They verged on being overdone. The sensor did work, but not perfectly.

Katie Pilkington/CNET

Defrost chicken

Ry Crist/CNET

The Panasonic comes with an inverter turbo defrost function, and I defrosted one chicken drumstick per test. Weight is the determining factor for successful defrosting, so I weighed each chicken drumstick in ounces and found the closest corresponding weight on the microwave (display options are given in pounds by the tenth of the pound). This required a bit of rounding, but it gets pretty close to the actual weight.

The first drumstick I tested weighed close to 0.4 pound and the turbo defrost function defaulted to 1:30. The second drumstick was also close to 0.4 pound, so it defrosted for 1:30 as well. The third drumstick was 0.3 pound, and it defrosted for a short 58 seconds. To test how well the defrost function performed, I used a meat thermometer on various parts of each drumstick to determine temperature range. The temperature disparity was larger in the first two tests, with ranges from 33 degrees to about 55 degrees and one outlier reading of 83 degrees on the second test. The third test was the most successful, with every temperature reading coming in under 40 degrees.

Ry Crist/CNET

The other microwaves also had temperature ranges of various sizes. The takeaway here is that the defrost setting behaves a bit sporadically and temperature readings can vary a lot. If you're planning to cook your food immediately, this may not be a big issue, but if you want to be very thorough, stick it in the fridge overnight instead.

Water boil

I heated 8 ounces of water in a 16-ounce measuring cup. At the two-minute mark, the water had reached a rolling boil in all three tests. The Panasonic microwave reached a boil faster than the other three. That's most likely due to its 1,250-watt output.


Katie Pilkington/CNET

Behold the microwave burger test. This is a test that strikes fear into the heart of many a seasoned appliance reviewer (well, maybe just me). If you remember, I tested burgers in a Panasonic and a Frigidaire toaster oven not too long ago and got terrible results (we all did, in fact). However, the Sharp convection microwave has a grill function and it even comes with a grill rack, so burger testing was a necessary evil.

If you couldn't already tell from my dramatic language, I was not excited about the taste test. Interestingly, though, all of the microwaves cooked burgers that were surprisingly edible. Nothing amazing, but no mutant hellspawn, either (a la the toaster oven burgers). The Sharp was the expected winner because of its grill functionality and it did not disappoint. It definitely turned out the best burgers we sampled. It also took upward of 19 minutes to cook them.

The Amana, Panasonic, Whirlpool, and even the small GE countertop microwave in our own office kitchen made decent burgers without a fancy grill function in under five minutes. They definitely look a lot worse than the Sharp's results in the photos, but that's mainly because the Sharp cooked on a grill rack and was then transferred to a plate, whereas the others were cooked directly on the plate (and we forgot to tidy them up for the photos).

Ry Crist/CNET

If you're really into burgers and want to make slightly better ones in your microwave, the Sharp -- or another convection grill microwave -- might be a good choice for you. But, if you just want to make a burger in a hurry, any old microwave will do.


Megan Wollerton/CNET

I'm going to venture a guess here -- you probably haven't made eggs in a microwave. Well, me neither. So I was intrigued when I saw that the Panasonic Web site proudly displays an omelet recipe designed specifically for its microwaves with inverter heating technology.

As you know, inverter tech is supposed to cook delicate foods better than other microwaves. My question: Has anyone ever expected a microwave to make a good salmon fillet? Or an omelet, for that matter? If you're making an omelet in a microwave, you're probably going for speed and efficiency over quality. In other words, I wasn't sure how to manage my expectations.

With a healthy dose of skepticism, I followed Panasonic's two-egg omelet recipe, and the results were surprising. Like the burgers, all four of the microwaves made edible omelets. No, they weren't restaurant-quality, but they weren't bad either.

The Sharp convection microwave produced the best results: fluffy, tasty omelets. This is likely due to the Sharp's comparatively low wattage (900 watts) and its slow-cooking convection heating technology. The Panasonic came in at a close second. That isn't great considering the recipe was made by Panasonic for Panasonic inverter microwaves. The Whirlpool came in third, and the Amana came in fourth -- that's most likely due to their high wattage (1,200 watts) and lack of a specialty heating feature.

Should you really buy this thing?
I would not buy this microwave strictly for its inverter technology. If you want evenly cooked food, the absolute best bet still seems to be a lower wattage, a lower power setting, and/or convection heating. That's why the Sharp outperformed the Panasonic on the omelet test; if you want the best results, you're going to have to be patient.

Also, the sensor heating only worked sporadically, although we found that to be the case with all of these microwaves. Either the presets didn't account for weight differences, or the moisture sensor over- or undercooked the food. Either way, a bit of tweaking will be necessary. The question then becomes -- is it worth it to spend $300 or close to $500 (with the built-in kit) for a microwave with less-than-perfect advanced features?

I would say yes. You should consider this model for its internal capacity, wattage, design, and overall performance. That combination is hard to find in a $300 microwave. So, if those things are high on your priority list, this is still a good choice. The microwave has always been more of a convenience appliance; something you rely on for its efficiency rather than quality. Of course, you really hope for efficiency and quality, and I think the Panasonic NN-SD997S has struck a really nice balance between the two. You might just have to tweak the sensor from time to time.


Panasonic NN-SD997S microwave

Score Breakdown

Performance 8Usability 9Design 9Features 8