The economics of usage of the two items depends on the heat and the quantity of food. Note microwave converts electromagnetic radiation into heat, while the oven uses gas or electricity to cook. For effectiveness, the oven cooks faster than the microwave, the cheapest form of energy for oven is gas because it is cheap, but electric oven will take more energy to cook, while microwave has wattage between 600 to 1500 watts will take more energy and electricity.