pc (12/21/82)
When cooking small quantities, microwave ovens use less energy than conventional ovens and, in some cases, stove-top cooking. However, in many cases microwaves use considerably more energy. Two potatoes bake using less energy in the microwave, but six potatoes are much more economically done in a conventional oven (particularly a small, well insulated oven). Most vegetables cook with far less energy on the stove than in a microwave. Energy consumption goes up with the size of the piece of meat and at some point (depending on the meat) uses much more energy than conventional cooking. A good rule of thumb is probably: if two cooking methods take comparable amounts of time, the microwave method probably uses far more energy. By the way, although I've seen no one mention it, I have had good success with cakes. It took awhile to get the timing right. A warm coffee cake after dinner is a nice treat and can be thrown together while the coffee/tea is brewing and the table is being cleared. It did take practice, however. P. Collins HP Labs, Palo Alto CA
jb (12/27/82)
I'm having trouble understanding how making six potatoes in a microwave oven can consume much more energy than using a conventional oven. Where does all the extra energy go? Granted that the transformer in the microwave unit will heat up as well as the potatoes, but the conventional oven uses energy to heat up a significant mass of metal to the same temperature as the potatoes, and maintains that temperature for a much longer time. Can someone enlighten me?
jim (12/29/82)
A microwave oven is an electronic device and operates at some efficiency less than 100%. Probably something like 60% of the electricity that goes in actually comes out as microwaves. The rest is dissipated as heat from the microwave tube and does little if any cooking. It is just vented into the room. A conventional electric oven converts > 99% (some is radiated as radio energy at harmonics of 60 Hz or as red light) into heat. If your conventional oven were perfectly insulated, it would consume less energy than your microwave for a sufficiently long cooking time. For shorter cooking times the microwave will do better because it doesn't have to heat up a massive oven interior. I don't have any hard figures on whether the microwave is more efficient or not. My conventional oven consumes about 2000 watts, but the element is not on all the time. A simple microwave (no probes or power settings) will consume 1200 watts or so continuously, but will be on for a shorter period of time. I suspect that a search of back issues of `Consumers Reports' would provide an answer to this, but I don't have the time to look. To put all this in perspective, consider that an automobile will consume about 70,000 watts of power at highway speed. A person consumes about 100 watts idling, and maybe as much as 1000 watts at peak output.