Inuheat PowerPacks feature very sophisticated electronics and include a “fuel gauge” that keeps track of how much electrical charge is in each PowerPack. As energy is released to heat your garment, the fuel gauge monitors the energy flow and can very accurately tell you how much remaining time you will have heating power at any given heat setting. This feature is unique to Inuheat and is very accurate. This gives you confidence to go enjoy your cold-weather pursuit without concern that you will run out of heat when you need it.