What it means?
The  BEE (Bureau of Energy Efficiency) India, in collaboration with the  International Institute of Energy Conservation, has come up with a star  rating system.
How it works?
The  star rating system is a way of measuring energy efficiency. It�s  applied to all electronic products such as refrigerators, TVs, ACs and  so on. Every AC model can get its EER tested and get a star rating.  Currently, it�s voluntary, not mandatory for companies to get a star  rating for their models. 
Benefits
Higher the Star rating of the AC, lesser is its power consumption.