Which AC unit uses the least energy?

ENERGY STAR Certified Room Air Conditioners

Many people buy an air conditioner that is too large, thinking it will provide better cooling. However, an oversized air conditioner is actually less effective - and wastes energy at the same time. Determine the square footage of the area you'd like to cool by using the ENERGY STAR square footage and this chart. Remember that bigger is not always better!

Many AC units have an EER in the 9's. These are just a little bit better.

	GREE GAC06AA-A3RNB5C	GE AJCQ06LCFQ1	Friedrich WS08C10D
Cooling Capacity (Btu/hr)	6450	6500	8000
Type	Through the Wall	Through the Wall	Through the Wall
Reverse Cycle	No	No	No
Casement Window	None	None	None
Energy Efficiency Ratio (EER)	10.4	10.4	10.4
Date Qualified	06/06/2013	09/09/2013	10/25/2013

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[PDF]list of qualifying models These qualify for a rebate because of being high EER