Americans, I'm so confused!! Do you really microwave water instead of boiling it with a kettle or jug? An el cheapo kettle costs like, $10.
Yes, I really microwave water sometimes. I'll use a stovetop kettle if I'm making a whole pot of tea, but if it's just one cup the microwave seems easier. I used an electric kettle in my office in grad school where I didn't have easy access to a stovetop or microwave on the same floor, but it has sat in my basement ever since.
Thanks to Retire-Canada for the link to relative efficiency numbers so I don't have to do my own science. :-)
It shows that an electric kettle is slightly more efficient than a stovetop kettle, which is in turn more efficient than the microwave. But the important note there is that for the kettles to be more efficient you need to boil exactly the amount you need; putting any extra water in there can easily nullify the advantage.