energy - Which is more efficient, heating water in microwave or electric stove?

So our propane tank in the kitchen ran out again today.

Which is more energy efficient, boiling water in a microwave on an electric stove? All things being equal i.e. starting temperature and mass of water.

Not so much about which is faster, but which will cost us less kWh generally.

I realize boiling from the stove noticeably heats up the environment as well, and continues emitting warmth long after its power had been switched off. Does the kettle have a higher thermal capacity than the micro-safe glass container (therefore needing to absorb more calories) or is that difference negligible with say 1kg of water? Haven't been inside a microwave to feel its thermal capacity/overhead though.

As far as dominant conduction/convection/radiation methods of transfer, it seems fairly obvious in both cases.

Answer

Looks like Ron Maimon is right, and the efficiency is pretty much the same for a microwave oven and an electric stove. There are some results of an actual comparison for boiling a cup of water (the method does not look very accurate though, and the models used are old) at http://michaelbluejay.com/electricity/cooking.html : 0.087 kWh for a microwave oven vs. 0.095 kWh for an electric stove. Furthermore, energy used for cooking does not make a large part of your energy bills anyway (http://www.aceee.org/consumer/cooking : "If you don’t cook much, more efficient cooking appliances won’t save much energy!").