You need to start the test with the temperature water you typically use backacking. It is amazing how much difference it makes. To save fuel I fill and solar heat a 2L platypus as soon as I get into camp. A few hours of sunshine will really heat it up, especially if you put a black stuff sack behind it. Heating breakfast water, cold from the night, takes almost twice as long. I have never had enough nerve to take the platypus inside my sleeping bag to keep the water warm for AM coffee.