Which is more efficient for boiling a cup of water, my microwave oven or my propane stove?
Is there a general calculation to compare propane or natural gas to electrcity for cooking?
Although the microwave itself is more efficient than the propane stove, that’s not the whole story. You have to consider the energy losses over whole cycle from burning propane to boiling water.
Using the stove, you burn propane and get 100% of the heat that can be released chemically, but perhaps 33% of this gets into the water.
Using the microwave, you start by burning propane (or more probably methane) in a power station to generate steam to turn a generator that sends electricity down a cable to your home. Because of the basic laws of heat engines and losses in transmission lines, only about 33% of the energy released gets into your home. And although the microwave is close to 100% efficient at transferring this energy to the water, the electronics that generate the microwaves are only 50% efficient (check the rating plate on your microwave — a 650W microwave consumes 1300W).
So the overall efficiency from gas to boiling water in this case is only about 16% — half as good as your simple propane stove!
Coleman Two-Burner Propane Stove