Panasonic NN-SB458S Review

The NN-SB458S is a sleek and modern-looking offering from Panasonic that gave satisfactory performance across our range of tests. It's smaller than many of the microwaves we tested, having a 10.6" turntable and measuring only .9 cu. ft., but is still big enough to accommodate most plates and foods.

Performance Comparison

Heating

Excelling most at leftover heating, the Panasonic scored well across our range of heating tests, aside from pizza heating. We use five distinct heating tests to evaluate how well each microwave heats. After testing 14 different microwaves, the average heating score came in at 5.8, and the NN-SB458S came in at 6.2, which is slightly above average overall.

Heat Map

To better understand how each microwave heats, we create a heat map by spreading an even layer of jet-puffed marshmallow creme on a circular piece of parchment paper cut to the size of the turntable, 10.6" in this case, and heating it on high for two minutes. We judge how well each microwave completes this task and that score contributes to 35% of the overall heating score.

We noted a small brown section in the center of the test disc and a larger, close-to-burnt ring around the perimeter that turned dark brown but not quite black. Ideally, we're looking for an even shade of color throughout the test disc or a symmetrical gradient as the color changes, indicating a smooth transition as temperatures increase. In this case, the middle and outsides seemed to heat much faster than the area in between, but nothing was burnt, netting the NN-SB458S a score of 6/10.

Heating Speed

The speed at which each microwave heats is tested by placing a beaker of 125 mL of refrigerated water in each microwave and then heated for 45 seconds on high. After heating, the beaker is removed from the microwave and we measure the temperature of the water to determine how much the water was heated. This testing metric contributes to 20% of each microwave's overall heating score.

Starting with a temperature of 59 degrees, we heated the water for 45 seconds, and the end temperature was 148, netting an increase of 89 degrees. Overall, the NN-SB458S scored 7/10 in our heating speed assessment.

Leftovers Heating

We loaded up a dinner plate with equal portions of mashed potatoes and green beans, along with 4 links of precooked breakfast sausages, to test how well each microwave heats leftovers. To keep results consistent, all of the food is refrigerated before heating. We selected the 12 oz dinner plate heat function (or equivalent function) on each microwave to perform this part of the testing.

The Panasonic's 12 oz heat function elected to add 4 minutes and 30 seconds to the clock and got to heating. It ended up with a score of 9/10 on this test, the highest leftover heating score of all the microwaves that we tested. We noted that each of the different foods was heated evenly and to a comfortable, edible temperature, averaging 154 degrees across all three.

Soup Heating

Taking into account the wattage of each microwave we tested, we allowed microwaves with less than 1,100 watts three minutes and microwaves with more than 1,100 watts two and a half minutes to heat a can of chicken noodle soup. Before measuring the temperature, we allow the heated soup to stand for one minute. We stir the soup with the thermometer and take temperature readings in different sections of the soup to come up with an average overall temperature.

Being a 900-watt microwave, the NN-SB458S was allotted three minutes to heat the soup. We felt that the soup was heated to just about the perfect temperature to eat right away, but, it would quickly become cold if not eaten right away. The temperature of the soup measured 153 degrees directly after being heated.

Pizza Heating

To test each microwave's pizza-heating capability, we take two pieces of pizza and heat them on high for 45 seconds. After heating, we use an infrared thermometer to determine the temperature range in multiple places on both pieces of pizza. We finish off our testing by eating the pizza and noting the different temperatures and textures the heating has affected.

The Panasonic performed average or better across most of our testing. However, it seemed to struggle with the pizza heating test. One slice of pizza was hardly heated at all, and the other had some hot spots, but the heating seemed patchy and uneven across the slice.

Frozen Foods

To evaluate how well each microwave in our lineup heats frozen foods, we selected four of the popular frozen foods to test with burritos, pot pies, lasagna, and hot pockets. We pop each frozen food into the microwave we're testing, heat it up according to the manufacturer's instructions, and then use temperature probes to take numerous readings. An ideal test result would heat the frozen food to an ideal eating temperature and have an even spread of heat throughout the food with little to no cold spots.

In our testing of the NN-SB458S, the frozen burrito was heated up to an ideal average temperature of 181 degrees and had very little variation in the temperatures taken throughout the burrito. The lasagna test didn't fare as well as the burrito, a few spots met or exceeded the ideal temperature of 165 degrees but there were quite a few cold sections, and the largest swing was a whopping 52 degrees lower than the high of 180 degrees. The hot pocket heated well, with only a seven-degree difference between temperatures on average. The pot pie heat test scored well as well, showing only a six-degree temperature difference on average, and in all places the probe measured, the temperature was above the minimum of 165 degrees.

Defrosting

Using one lb. of frozen ground meat, we freeze the meat overnight to make sure to keep test results consistent and then use each microwave's defrost setting to see how well they can determine the correct amount of time needed and defrost the meat without cooking it, only flipping if the microwave instructs to do so. We measure the weight of the meat before and after, the more the weight drops, the better the defrosting performance.

In our test, the NN-SB458S selected ten minutes and twenty seconds to defrost the frozen ground meat and instructed us to flip it halfway through the time allotted. None of the ground meat was cooking during the defrosting, and very little of the meat was still somewhat frozen. We felt that it defrosted well enough that it would be ready to cook in the state that it finished.

Ease of Use

To complete our ease-of-use assessment we review each microwave's quick buttons, interior lighting, timer, friction when placed on multiple different surfaces, and how well the popcorn setting works.

The NN-SB458S lacks quick start buttons that require just one touch to get things heating, the lighting too, is less than optimal. The timer is simple enough and easy to use, but when measuring how much friction the microwave has when placed on different surfaces, it moved every time we touched it. Whether pushing buttons to start heating or opening and closing the door, this microwave could benefit from some rubber feat to hold it in place during use. The popcorn setting works very well, leaving behind only 9 unpopped kernels and no burning on any popped pieces.

Should You Buy the Panasonic NN-SB458S?

If you're looking for a microwave on a budget that is a solid performer across a wide range of tasks, the NN-SB458S may be right for you. However, if your microwave use often involves heating up pizza, this isn't the right microwave for you. Aside from the pizza heating, this microwave is an adequate performer at a fair price. The only caveat is some lack of ease-of-use features, which some other models perform better.

What Other Microwaves Should You Consider?

If, after reading this review, you think this may not be the right microwave for you, check out some of our other top performers identified during our testing. The Magic Chef MC110MB is a top pick that stood out in our testing especially when heating frozen foods. The GE JES1109RRSS is the best overall microwave that we reviewed and excels at each of the different metrics we tested, but that performance does come at a cost as it is also the most expensive microwave that we reviewed.