Best Microwave Ovens on Amazon. The efficiency of microwave ovens is efficient that is microwave kitchen appliances use electromagnetic radiation. The functionality of the microwave makes the cooking process interesting. Kitchen appliances use electromagnetic radiation. Heats food quickly and cooks it as well. It works by generating high-frequency radio waves. Which rapidly vibrates water, fat and sugar molecules in food. These built-in combo ovens are the most advanced in consumer test reports in terms of heat generation. And it’s ideal if you’re short on counter space. The beauty of a separate cook top and wall oven is that it has a lot more flexibility in a simple design. Such as a cook top on an island that is for example, an oven is installed at a height on the other side of the kitchen.