According to the average monthly data of OA “KEZ” from January 2010 until March 2011 for two series of electrolysis, working at the plant, a regression analysis of the dependences of the average voltage, current yield, specific consumption of electricity from the water vapor pressure in atmospheric air (P) was performed. Increase in P by 10 mm Hg does not affect the amount of working interference, increases the current efficiency by 0.480. 63%, reduces the specific power consumption by 73-78 kW • h/t. The observed regularities are explained by a decrease in the fluorine content in flowing into the cryolite-alumina melt of alumina by the removal of desorbed hydrogen fluoride with water vapor in the presence of fluorinated alumina in the range of APG punching.