A microwave oven uses less energy than a conventional oven. Even though this statement is broadly true, a microwave oven isn’t always the most efficient way to cook.
So what appliance should you use to heat up or cook your dinner: A gas stovetop? An electric-resistance stovetop? An induction stovetop? A gas oven? An electric oven? A countertop toaster oven? A crockpot? Or a microwave oven?
If all you care about is energy efficiency, it’s possible to come up with an answer to this question — but the answer will depend on the quantity and the type of food you are cooking.
If you care about the taste of your food, on the other hand, energy efficiency probably doesn’t matter. For example, if you are cooking a traditional paella, the answer is, “An open fire fueled by prunings from a vineyard” — and energy efficiency be damned.
A microwave oven uses quite a bit of power — between 950 and 1,720 watts — but it usually isn’t operated for long. According to a 2001 Home Energy article, “the typical residential microwave oven consumes about 110 kWh of electricity per year.” If you are paying 15¢/kWh for electricity, your microwave oven is costing you only about $16 a year to operate.
According to The Consumer Guide to Home Energy Savings, a publication of the American Council for an Energy-Efficient Economy, cooking a casserole costs 16¢ if you use a conventional electric oven; 8¢ if you use a toaster oven; 7¢ if you use a gas oven; 6¢ if you use an electric crockpot; and 3¢ if you use a microwave oven. (These calculations are based on the assumption that natural gas costs 60¢/therm, and electricity costs 8¢/kWh. To bring these estimates roughly in line with current energy prices, the estimated costs should be increased by 40% to 100%.)
However, there are many factors…