A microwave is more economical than a stove when it comes to cooking most food. However, when using the burners on an electric stove to boil water, for instance, the range is slightly more economical.
The reason microwaves are more economical for most uses is because they heat and cook much faster than a traditional oven, and their heat waves are focused. Information from the Energy Star program estimates that reheating or cooking small portions of food in a microwave may save up to 80 percent of the energy used compared to using a traditional oven. Keeping a microwave clean increases its efficiency, as well.