There is no way to rate a vaporizer as most efficient in absorption, as each persons lung capacity is different and can absorb at a different rate. No vaporizer can claim that it can make your lungs absorb the most efficient unless its custom designed for your needs. There is just no way to make this claim. Efficiency in vapor rate? Can you please better explain to me how what this means as im trying to figure out what it is your trying to say with this one. You are talking about vapor production as in how fast it can produce vapor? Some people are cloud chasers and some people are not. Having a vaporizer that can deliver a large cloud or as small as needed or as much as needed is the ideal picture, but having a vaporizer that can only deliver small wisps or very thin vapor then that vaporizer has limits. As for amount used to produce vapor, there is science involved in that a little bit but at the most it has to do with vaporizable content. It has to do with the temperature drops when cold air is introduced into the air stream. Example is Thc Vaporizes somewhere around 380-400, well lets say you have your temp at 390 when no cold air is introduced if constant 390 is achieved then the vapor production will be greater then lets say a vaporizer that starts at 390 but as more you pull the cooler it gets and less vapor is produced. This brings me to the point of the amount of vapor produced per load is based on how hard you ride the button to keep the temperature in the ideal range. There are vaporizers that can produce massive amounts of vapor on a .15 load because they keep the temperature steady even when cold air is introduced into the air path. The amount of vapor produced will be also depended on the vaporizable content like i said. One can only claim that the temperature never drops due to cold air being introduced into the air path. It can be efficient in keeping the ideal temperatures but thats about it. Now when you go into efficiency all these have to be taken into consideration but they are not big players. How efficient is the heater? How efficient is the battery? That is what makes or breaks a vaporizer. If a vaporizer can not vaporize, or can not constantly provide vapor even if cold air is introduced into the air path, and can not vaporize more then lets say .5 without it needing a charge then its not efficient at all. Now when you look at the numbers you will see that not only Does the Hercules 3.7v vaporize more herbs per charge, not only does it keep producing vapor even if cold air is introduced into the air path, not only does it provide with as little or as much as possible with the given heater, I would say it is most efficient. Because You can get .7-.9 per charge. You can regulate the vapor production with the button. Vapor production stays the same even cold air is introduced Now when you take all three and you have other models to compare it with, and the other models do 2 out of the 3 but can not match lets say the battery efficiency then you have a clear choice. Sorry for the rambling but this is my understanding and i might be wrong, but it has gotten the job done so far.