I've been boiling water in a microwave for years......I use a measuring cup, 2 cups worth....3.5 minutes in my microwave.  I use the water for "cup o' noodles" and for making Jello..........plus the occasional cuppa.......

My bete noir is the frozen burrito........I one accidently nuked one for upwards of 20 minutes (although I really don't know at what point the microwave gave up the ghost......You ever see a fireplace log in the morning, black and ashy, with an eerie glow deep within?  That was my burrito.