I just ran the identical test...everything the same except the temperature (it's -20 C tonight) and something unexpected happened.

The water boiled in about the same time but this time the stove ran for a mind boggling 31 minutes! 10 full minutes longer than what it's rated to do. I wouldn't have believed it if I had not have been sitting out in the cold with a digital probe thermometer freezing my buns off watching it go.