Sorry, I thought you were on a wind up! From your original figures, the efficiency would be 100% (obvs). Wind back a couple of pages to the equation Joeman and JRH gave and stick eta in there, rearrange and insert the actual input/output values. That will allow you to calculate the efficiency of the unit. You can then account for the characteristics of the components pre and post the unit and calculate the absolute current draw. This value will only be applicable for a specific environment so if you change temperature for example, the calculated value will change a bit. I reckon it'll be between 4 and 5 though. You like 5 so we'll go with that.