Panasonic NN-ST665B Specs: What They Mean for Your Kitchen

The Panasonic NN-ST665B is a 27-liter inverter microwave oven with a 1000W output, designed to cook food more evenly and defrost it faster than conventional microwaves. For your kitchen, these specs mean you get a large-capacity oven that can handle whole roasts and large casseroles, while the inverter technology gives you precise, consistent power that prevents overcooked edges and undercooked centers. This article explains each key specification in plain language, so you can decide if this model fits your cooking habits and counter space.

Formula

The calculator above estimates the energy consumption of your microwave based on the cooking time and power level. The formula is:

Energy (kWh) = (Time in minutes / 60) × (Power in watts / 1000)

Where:

• Time = cooking time in minutes (e.g., 5 minutes)
• Power = microwave output power in watts (e.g., 1000 W)
• Energy = electricity used in kilowatt-hours (kWh)

To estimate the cost, multiply the energy by your electricity rate (the calculator uses a default of $0.15 per kWh, but you can adjust this in your head or use a different calculator).

Worked Example

Using the default values from the calculator: 5 minutes at 1000 watts.

1. Convert minutes to hours: 5 / 60 = 0.0833 hours
2. Convert watts to kilowatts: 1000 / 1000 = 1 kW
3. Multiply: 0.0833 hours × 1 kW = 0.0833 kWh
4. Cost at $0.15/kWh: 0.0833 × 0.15 = $0.0125 (about 1.3 cents)

So a 5-minute cook at full power uses roughly 0.083 kWh and costs about 1 cent. This matches the calculator’s output (rounded to 0.083 kWh and $0.01).

What the 27-Liter Capacity Means

The 27-liter (about 0.95 cubic feet) interior is the largest category for countertop microwaves. It fits a 12-inch dinner plate comfortably, a 9×13-inch baking dish, or a 5-quart casserole. For families or people who batch-cook, this capacity means you can reheat a full lasagna or cook a whole chicken in a microwave-safe roaster. However, it also takes up more counter space—roughly 19 inches wide, 15 inches deep, and 12 inches tall—so measure your space before buying.

Inverter Technology: Why It Matters

Traditional microwaves use a transformer that turns the magnetron on and off in cycles. When you set 50% power, the oven runs at full power for a few seconds, then shuts off for a few seconds. This causes hot spots and uneven cooking. Panasonic’s inverter technology instead delivers a continuous, steady stream of power at any level from 10% to 100%. For delicate tasks like melting chocolate or defrosting frozen meat, this means no scorched edges and no partially frozen centers. The inverter also allows for a more compact power supply, which is why this oven is relatively slim for its capacity.

1000 Watts: How Fast Is It?

The 1000W output is on the higher end for home microwaves (typical models range from 700W to 1200W). Higher wattage means faster cooking and boiling. For example, boiling 2 cups of water takes about 2 minutes at 1000W versus 3 minutes at 700W. This speed is a plus for busy kitchens, but it also means you need to adjust cooking times from lower-wattage recipes. If you’re used to a 700W oven, reduce cooking time by about 30% when using this Panasonic. The inverter’s precise control helps avoid overcooking, but you should still check food earlier than the recipe suggests.

Defrosting and Sensor Cooking

The NN-ST665B includes a defrost function that uses the inverter to deliver low, even power, which is much better than the on-off method. It also has a humidity sensor that detects steam from food and automatically adjusts cooking time and power. This is useful for reheating leftovers or cooking frozen vegetables—you don’t have to guess the time. For best results, use the sensor reheat for foods with consistent moisture, like soup or rice, and cover dishes to help the sensor read humidity accurately.

Common Problems and How to Avoid Them

One common issue is uneven defrosting if you don’t turn the food halfway through. Even with inverter technology, thick items like a whole chicken benefit from a pause to break apart pieces. Another problem is using metal containers—this oven, like all microwaves, must only be used with microwave-safe cookware. Also, the inverter system can be more sensitive to power surges; plugging it into a dedicated circuit is recommended to avoid tripping breakers. Finally, the turntable (which is 34.5 cm in diameter) can be removed for cleaning, but make sure it’s properly seated before use.

Comparing to Other Microwaves

Compared to a standard 700W microwave, the NN-ST665B cooks faster and defrosts more evenly, but it costs more. Compared to a 1200W model, it’s slightly slower but uses less energy and is gentler on delicate foods. The inverter technology is a significant upgrade over traditional models, but if you rarely defrost or cook at low power, a cheaper non-inverter microwave might suffice. Also, this Panasonic is a countertop model—it’s not designed for built-in installation, so ensure you have adequate ventilation space (at least 3 inches on the sides and back).

Safety and Usage Tips

Always use microwave-safe containers: glass, ceramic, and plastic labeled “microwave safe.” Avoid metal, aluminum foil, and dishes with metallic trim. When heating liquids, use a wooden stir stick or microwave-safe object to prevent superheating (when water heats above boiling point without bubbling, then erupts). For baby food or formula, always stir and test temperature before serving. Never run the oven empty, as this can damage the magnetron. Keep the door seals clean to prevent leaks, and if the door doesn’t close properly, stop using the oven and have it serviced.

Frequently Asked Questions

Q: Can I use metal in the Panasonic NN-ST665B?
No, metal should never be used in any microwave, including this one. Metal reflects microwaves, causing sparks and potential fire. Use only microwave-safe glass, ceramic, or plastic.

Q: How do I clean the inside without damaging the inverter?
Unplug the oven, remove the turntable, and wipe the interior with a damp cloth and mild detergent. Avoid abrasive pads and harsh chemicals. Do not submerge the oven in water.

Q: Is the inverter technology worth the extra cost?
If you regularly defrost meat, melt chocolate, or cook delicate sauces, yes—the even power prevents hot spots and gives better results. If you mostly reheat leftovers, a standard microwave may be sufficient.

Q: What does the “sensor” do exactly?
The humidity sensor detects steam released from food as it heats. It automatically adjusts the cooking time and power to prevent overcooking. For example, reheating a bowl of soup, the sensor stops when the soup is steaming evenly.

Q: Does this microwave need a special outlet?
It uses a standard 120V outlet, but because it draws about 1500W, it’s best to plug it into a circuit that isn’t shared with other high-power appliances to avoid tripping the breaker.

Q: Can I bake or grill in this microwave?
No, this is a standard microwave only—it does not have convection or grill functions. For baking or grilling, you’d need a convection microwave or a separate oven.

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in t | Cook time | min | 5 | 0
in p | Power level | W | 1000 | 100
out energy | Energy used | kWh | (t / 60) * (p / 1000) | 3
out cost | Cost at $0.15/kWh | USD | ((t / 60) * (p / 1000)) * 0.15 | 2