http://www.brightsideofnews.com/news/2009/10/14/columbia-footwear-now-selling-bugathermo-rechargable2c-heated2c-boots-.aspx overall rating -25F/-32C. This is without even turning the heating element on.
have three settings, Low, Medium and High; each of these settings provides a different level of heat and also affects your battery life. When running on low the heating element can generate up to 113F/45C of internal heat [at the heating pad], this gives you an estimated battery life of about eight hours. On Medium you get a toasty 122F/50C and roughly six hours of battery. If you are so cold as to need the high setting you are looking at an almost uncomfortable 140F/60C and four hours. The temperature setting is controlled through a button on the side, next to this button is a set of three lights that indicate the temperature level you are currently on.
*****
http://gearjunkie.com/Columbia-Bugathermo-and-Snow-Hottie-bootsIn short, Columbia has missed the aforementioned Holy Grail by a long shot. The Bugathermos are clunky and uncomfortable. Design flaws include a bad fit on the top of the midfoot area, where boot flex causes material to fold over and press into your foot. Fit around the calves was uncomfortable and loose on long hikes.
And the embedded heaters? I could barely feel the warmth. When hiking on a 10-degree day with the heat turned on for one foot, but off for the other, my feet felt about the same.
To be sure, Thinsulate insulation keeps these boots warm. I could walk in the snow for long periods on zero-degree days with no issue. But the internal heater, powered by lithium-polymer batteries, was almost unnoticeable.
