http://www.whirlpoolindia.com - Purchasing a window AC is something that troubles many people. However, from an energy efficiency point of view, there is no preferred pick. Both of them can be equally effective. What matters is EER. EER illustrates the amount of temperature reduction an AC is able to offer per watt of electricity it uses. Offices of energy efficiency, assess them on its star evaluation, founded on EER of ACs. Higher the Energy Efficiency Ratio, higher the star rating it will have. Hence, a five star rated AC offers more temperature reduction per watt of electricity consumed.