Just as a point of reference for you. I use a small portable propane heater that advertises to produce 3800 BTU/hr. SO this would equate to roughly 1,100 (3.4 BTU = 1 watt). You are talking about a quarter of that. My heater doesn't turn the blind into a sauna......it simply takes the sting out of the cold and makes it less miserable. Now my blinds are not insulated or sealed real well and propane means I have to have a window open to vent the fumes as well. The idea of heat without the fumes is great, but I am not sure how long a battery is going to provide that heat source. Batteries ain't cheap, and lugging one back and forth won't be fun either....especially in the cold. My propane heater stays in the blind and I simply bring a 16oz bottle with me if needed (I tend to keep a couple in the blind once it gets cold and thru hunting season) and one of these bottles last 5 to 6 hours.