Bikram yoga, or "hot yoga," is conducted in a room that is heated somewhere around 105 degrees Fahrenheit. The Bikram method consists of a set series of 26 poses, but not all instructors or classes follow the series. Doing these poses in heat is meant to make you sweat more, thus flushing more toxins from the body. The heat also encourages muscle flexibility.
It's quite possible that you might burn more calories doing hot yoga, not only because of the temperature, but also as your muscles loosen in the heat and you are likely to go deeper into challenging poses. On average, a 150-pound woman may burn about 680 calories performing 60 minutes of Bikram yoga.
However, you're likely to find that calories burned is just a bonus to practicing Bikram yoga; the flexibility, peace of mind, awareness of your body and the feeling of your body being "cleansed" far outweighs any notion of calorie burning.
Note that Bikram yoga may not be for everyone. The heat may cause or aggravate health issues as it raises your core body temperature. Pregnant women should avoid doing Bikram yoga unless it's cleared by their doctor. And anyone with health conditions, such as high blood pressure, or those who are not currently exercising should clear any type of exercise regime with their doctor before beginning.
The same precautions listed in the previous post should be followed with power yoga.